manojsir-science blog

SCIENTISTS' HIDE & SEEK : A JOKE

2009-08-31T01:29:00.001-07:00

Once all the scientists die and go to heaven. They decide to play hide-n-seek.

Unfortunately Einstein is the one who has the den...He is supposed to count upto 100...and then start searching...

Everyone starts hiding except Newton...

Newton just draws a square of side 1 meter and stands in it right in front of Einstein.

Einstein's counting 1,2,3...,97,98,99,100...He opens his eyes and finds Newton standing in front...

Einstein says " Newton's out...Newton's out..."

Newton denies and says "I am not out...I am not Newton..."

All the scientists come out to see how he proves that he is not Newton.

Newton says "I am standing in a square of area 1 meter squared...That makes me Newton per meter squared...Since one Newton per meter squared is one Pascal, I'm Pascal, Therefore Pascal is OUT...!!!!!!!!!

ENVIRONMENT AND ENVIRONMENTAL PROBLEMS - III : LONG ANSWERS

2008-08-27T01:03:00.000-07:00

GIVE ANSWER IN DETAIL

*INDEX-TOPIC SEARCH

Describe sources of air pollution in brief.
ANS :

The two types of sources of air pollution are : Natural sources and man-made sources.
Natural sources(factors) polluting the atmosphere are : volcanoes, forest fires, decaying plants, storms, pollen grains, lightening-induced chemicals, etc.
Man-made sources of pollution are : Burning of firewood, burning of fossil fuels, automobile smoke, aeroplanes, power stations, industrialisation, agriculture, wars, atomic explosions, deforestation, mining, oil refineries, etc.

Mention harmful effects of water pollution.
ANS :

Mercury mixed with water causes the disease Minamata. It is a poisonous disease and may cause death. It was first observed in coastal area of Minamata city of Japan.
Chemicals like mercury, cadmium, cobalt, etc. present in water cause diarrhoea.
Biological Oxygen Demand(BOD) of clean water is less. BOD of polluted water increases and harms aquatic organisms, sometimes causing their destruction.
Accumulation of domestic sewage and fertilisers results in the increase of nitrates and phosphates in water. These promote the growth of algae and other microorganisms. Thus, there is excessive loading of aquatic ecosystem with nutrients and algal growth, a phenomenon called eutrophication. Due to eutrophication BOD increases and organisms die.

Describe the interrelationship between population, environment and development.
ANS :

Exploding population at increasing speed has become a major problem to environment and development at global level.
Increase in population leads to increase in demand for food. This leads to increase in the use of fertilisers and pesticides.
Excessive use of fertilisers and pesticides causes pollution which has direct and indirect effect on human health.
Increasing demand for space due to population explosion results in encroachment of fertile and agricultural land, forests and habitat of wild life.
To maintain the existence of human life, the balance between population, environment and development must be maintained.

List out different laws for environmental protection.
ANS :For the protection and conservation of environment, following laws have been enacted by the Government of India :

Environment (Protection) Act, 1986
Forest (Conservation) Act, 1980
Water (Prevention and Control of Pollution) Act, 1974
Wildlife (Protection) Act, 1972
The Motor Vehicle Act, 1983
Prevention of Cruelty to Animals Act, 1966
Air (Prevention and Control of Pollution) Act, 1981
The Insecticide Act, 1968

Describe harmful effects of air pollution.
ANS :

Burning sensation in eyes, nose and throat.
Diseases of lungs like bronchitis, asthma, etc. caused by pollutant gases like SO₂ and NO₂.
Diseases of respiratory system spread through dust particles. Silicosis is caused by silica and asbestosis is caused by asbestos.
Cancer caused by carcinogenic pollutants.
Heavy metals inhaled through air cause poisonous effects.
Increase in ultraviolet radiation reaching earth due to depletion of ozone layer causes skin cancer, damage to eyes and damage to immune system.
Dissolution of atmospheric gases like SO₂, SO₃, NO₂ in moisture results in formation of sulphuric acid and nitric acid. This causes acid rain which harms organisms, various monuments and buildings.
Carbon dioxide and methane absorb heat and increase the temperature of earth's atmosphere. This is known as Greenhouse effect. This increase in temperature results in melting of ice on polar regions and causes sea level to rise.

Write a descriptive note on Prevention and Control of Air Pollution.
ANS :Two types of methods are used for prevention and control of air pollution :

Methods for controlling gaseous pollutants :

Combustion : This method is used for pollutants in the form of organic gases or vapours. These pollutants are converted into water vapour and relatively less harmful products such as CO₂ by flame combustion or catalytic process.
Absorption : In this technique, the gaseous effluents are passed through specific scrubbers or absorbers. The gaseous pollutants are absorbed and air is purified.

Methods for controlling particulate emissions :

Wet Scrubbers : Wet scrubbers are used in chemical, mining and metallurgical industries to trap SO₂, NH₃, metal fumes, etc.
Electrostatic Precipitators : The gas or air stream containing aerosols in the form of dust, fumes or moisture is passed between two electrodes. The aerosol particles get precipitated on the electrodes.

NOTE : The diagram in the textbook showing WET SCRUBBER is actually the diagram of BAG FILTER.
Describe prevention and control of water pollution.
ANS :Sewage treatment and Oxidation pond are the two methods of controlling water pollution.

SEWAGE TREATMENT :

This method involves three steps.
During first step, large components and suspended matter are isolated by sedimentation and converted into harmless matter which can be used as fertiliser.
During second stage, air containing oxygen and bacteria is passed through water in an aeration tank. The bacteria degrade organic substances. Then chlorination is performed.
During tertiary(third) stage, substances like nitrates and phosphates are removed to obtain clean water.

OXIDATION POND :

This method, developed by National Environment Engineering Research Institute(NEERI), Nagpur, is used to treat industrial effluents and sewage.
Oxidation pond is a shallow pond where domestic as well as industrial waste matter is stored.
This water is mixed with microorganisms and algae which oxidise carbonic components present in water and water gets purified.

ANS :

ENVIRONMENT AND ENVIRONMENTAL PROBLEMS - II : BRIEF ANSWERS

2008-08-24T08:14:00.000-07:00

ANSWER IN BRIEF

*INDEX-TOPIC SEARCH

Mention types of environment with examples.
ANS:

Physical environment : atmosphere, lithosphere, hydrosphere.
Biological environment : plants, animals, microorganisms.
Cultural environment : social traditions, economic, political.

Draw a chart showing types of environment.
ANS:[SEE THE CHART]

Mention various environmental problems.
ANS:Various environmental problems include :

Decrease in habitat of wildlife
Wastage of water
Deforestation
Soil erosion
Desertification
Depletion in biodiversity

Write a few sentences on air pollution.
ANS:

The transparent layer of gases surrounding the earth is called atmosphere.
In balanced atmosphere the ratio of various gases is fixed.
When this balance is disturbed due to any reason, it is called air pollution.
The major reasons for air pollution are population explosion, urbanisation, industrialisation and heavy transportation.

Mention natural sources of air pollution.
ANS:Natural sources of air pollution are : volcanoes, forest fire, storms, pollen grains, dust particles, decaying plants, lightening-induced chemical reactions, etc.

Mention man-made sources of air pollution.
ANS:Man-made sources of air pollution are : Burning of firewood, burning of fossil fuels, industrialisation, agriculture, smoke from automobiles, aeroplanes, wars, atomic tests, deforestation, power stations, mining, oil refineries, etc.

Explain : Acid rain.
ANS:

Combustion of fuels and industrial smoke add pollutant gases like NO₂, SO₂, etc. in the atmosphere.
These gases dissolve in moisture present in air and form acids like nitric acid and sulphuric acid.
When these acids come back to earth through rain, it is called Acid Rain.
Acid rain harms various organisms, monuments and buildings.

Explain : Greenhouse effect.
ANS:

Gases like CO₂ and methane have the property of absorbing heat.
These gases, when present in atmosphere, absorb the heat of the sun rays reflected by the earth.
This results in the warming of earth's atmosphere.
This is called Green-House Effect.
Due to Greenhouse effect, the ice on polar regions may melt increasing the sea level.

Describe the methods for controlling gaseous pollutants.
ANS:[Refer to Long Answer about prevention and control of air pollution]

Describe the methods for controlling particulate emissions.
ANS:[Refer to Long Answer about prevention and control of air pollution]

Mention sources of water pollution.
ANS:The sources of water pollution are :

Industries
Population explosion
Sewage
Pesticides and fertilisers
Radioactive waste
Oil(spillage of oil)
Heavy metals
Harmful microorganisms.

Describe sewage treatment.
ANS:[Refer to Long Answer about prevention and control of water pollution]

Describe Oxidation Pond method.
ANS:[Refer to Long Answer about prevention and control of water pollution]

List out pollutants causing land pollution.
ANS:Pollutants causing land pollution are : fertilisers, ashes, coal, domestic waste, paper, card board, plastics, rubber, clothes, metals, glass, construction materials, dead bodies of animals, insecticides, radioactive waste, etc.

Mention effects of land pollution.
ANS:

Agricultural land becomes less fertile.
Insoluble pesticides like DDT decrease the secretion of sex hormones as well as the calcium level.
Soil erosion occurs. The amount of soil washed out in 6 months can be sufficient to make bricks needed to construct houses of entire world.

Describe the main points for prevention and control of land pollution.
ANS:

The pollutants can be decomposed and removed through biological processes.
They can be converted into organic fertilisers.
Non-decomposable waste can be used to fill up the pits.
Specific incinerators can be used for final disposal of waste.

Write about biodegradable pollutants.
ANS:

The pollutants which can be decomposed by microorganisms are known as biodegradable pollutants.
Faecal matter, solid sewage waste, domestic waste, agricultural waste, paper, wood, clothes, etc. are biodegradable.

Write about non-biodegradable pollutants.
ANS:

The pollutants which cannot be decomposed by microorganisms are known as non-biodegradable pollutants.
Pesticides like DDT, mercury, lead, aluminium, arsenic, plastics, etc. are non-biodegradable.
These pollutants remain for a long time in environment and enter the organisms through food chain and biogeochemical cycle.
Then they get accumulated in large amount in their bodies, a phenomenon called biomagnification.

Write a few points about environmental balance.
ANS:

Environmental balance is essential for all organisms including man.
Pollution leads to the loss of environmental balance.
Environmental imbalance causes harmful effects on life of organisms.
Judicious use of non-renewable sources is necessary for the maintenance of environmental balance.
Personal as well as social awareness regarding environment like keeping one's surroundings clean automatically helps in the maintenance of balanced environment.

Write some points about conservation and protection of environment.
ANS:

Conservation of environment means prevention of excessive use of such activities which provide individual and commercial benefits and lead to environmental damage.
Almost all countries in the world have made laws for the conservation of environment. These laws help protect and Conserve environment.
One should be aware of such laws to make it possible to protect and conserve environment.

Describe environmental problems.
ANS:

Activities of man continuously disturb the environment and create various problems.
Population explosion, industrialization and other human activities create following problems :

Decrease in habitat of wildlife
Wastage of water
Deforestation
Soil erosion
Desertification
Depletion in biodiversity

Why do aquatic animals die in polluted water ?

ANS: Due to pollution of water by domestic sewage and fertilizers there is an increase in nitrate and phosphate components. these components cause many fold growth of algae and other micro-organisms. This is called eutrophication and due to it the biological oxygen demand (BOD) of the aquatic ecosystem increases and the organisms die.

ENVIRONMENT AND ENVIRONMENTAL PROBLEMS - I : MCQs & SHORT ANSWERS

2008-08-22T23:59:00.000-07:00

*INDEX-TOPIC SEARCH

MULTIPLE-CHOICE QUESTIONS

SELECT THE CORRECT ALTERNATIVE:

Which of the following is a greenhouse gas ?

Methane
Oxygen
Nitrogen
Hydrogen

______ is used to convert organic pollutants into water vapour and CO₂.

Electrostatic precipitator
Flame combustion
Absorption
Wet-scrubber

______ are used in electrostatic precipitators.

Catalysts
Absorbers
Electrodes
Chemicals

Biological oxygen demand of ______ is the least.

sewage
sea water
pure water
polluted water

Compounds of ______ cause Minamata disease.

mercury
cadmium
cobalt
fertilisers

Due to eutrophication______.

BOD increases
BOD decreases
algae are destroyed
water becomes less harmful

______ is the first step of sewage treatment.

Precipitation
Chlorination
Sedimentation
Aeration

World Environment Day is celebrated every year on ______.

5th March
15th April
15th May
5th June

We and our surroundings together are called...

environment
atmosphere
lithosphere
hydrosphere

Which of the following is not an environmental problem ?

Wastage of water
Conservation of water
Deforestation
Land erosion

Volcano is ______ source of pollution.

artificial
natural
both
man-made

Which rays strike on earth due to depletion of ozone layer ?

Ultraviolet
Infrared
Visible light
Microwaves

Which method is used for the removal of sulphur dioxide and ammonia from the polluted air ?

Wet scrubbers
Absorption
Gravitational method
Electrostatic precipitator

BOD is ______ in polluted water and ______ in potable water.

more, less
less, medium
medium, more
less, more

Which of the following is responsible for acid rain ?

Hydrogen
Oxygen
Sulphur dioxide
Methane

Which pollutants are responsible for bronchitis ?

O₂, CO₂
CO, CO₂
SO₂, NO₂
Cl₂, H₂S

Which method is used to control pollutants of particulate nature ?

Combustion
Absorption
Electrostatic precipitators
Oxidation pond

ANSWERS TO MCQs

(1) A (2) B (3) C (4) C (5) A (6) A (7) C (8) D (9) A (10) B (11) B (12) A (13) A (14) A (15) C (16) C (17) C (18)

SHORT QUESTIONS

ANSWER IN SHORT:

What does 'environment' mean ?

ANS :The social, economical, physical and chemical factors surrounding an organism are collectively known as 'environment' for that organism.
What is studied in environmental biology ?

ANS :The interrelationship between organisms as well as between living and nonliving components is studied in environmental biology.
Mention types of environment.

ANS :Types of environment are : (i)Physical environment (ii)Biological environment (iii)Cultural environment.
Mention the major reason for environmental problems.

ANS :Population explosion is the major reason for environmental problems.
Define : Pollution.

ANS :Pollution is an undesirable change in the physical, chemical or biological characteristics of air, water and soil.
Mention common pollutants.

ANS :Various gases, heavy metals, pesticides, fertilisers, radioactive materials, high temperature, etc. are major pollutants.
Mention types of pollution.

ANS :Air pollution, water pollution and land(soil) pollution.
What is atmosphere?

ANS :The transparent layer of gases surrounding the earth's surface is called atmosphere.
Mention common causes for air pollution.

ANS :Urbanisation, population explosion, industrialisation and heavy transportation are common causes for air pollution.
Mention respiratory diseases caused due to air pollution.

ANS :Asthma, bronchitis, silicosis and asbestosis are diseases caused due to air pollution.
Mention pollutants causing asthma and bronchitis.

ANS :SO₂ and NO₂ are pollutants causing asthma and bronchitis.
What are carcinogens ?

ANS :Substances causing cancer are called carcinogens.
What rae the effects of depletion of ozone layer ?

ANS :Depletion of ozone layer increases the amount of ultraviolet radiation reaching the earth which, in turn, causes skin cancer and damages eyes and immune system.
What is Greenhouse Effect ?

ANS :The warming up of earth's atmosphere due to absorption of heat by gases like CO₂ and methane present in the atmosphere is called Greenhouse Effect.
Which type of pollutants cause air pollution ?

ANS :Gaseous and particulate pollutants cause air pollution.
What is water pollution ?

ANS :The mixing of undesirable chemical, physical or biological components with pure water is called water pollution.
What is the full form of BOD ?

ANS :The full form of BOD is Biological Oxygen Demand.
What is Eutrophication ?

ANS :The pollution caused due to growth of algae and other microorganisms under the influence of nutrients is called Eutrophication.
Which components promote algal growth in water ?

ANS :Compounds having nitrates and phosphates promote algal growth in water.
What is the full form of NEERI ?

ANS :NEERI stands for National Environment Engineering Research Institute.
Mention prime causes for land pollution.

ANS :Urbanisation, population explosion and industrialisation are prime causes for land pollution.
Mention solid waste pollutants causing land pollution.

ANS :Faeces of humans and other animals, dead bodies and domestic waste are solid pollutants causing land pollution.
How are pollutants classified ?

ANS :Pollutants are classified as biodegradable and non-biodegradable pollutants.
What is meant by biodegradable pollutants ?

ANS :The pollutants which can be decomposed by microorganisms are called biodegradable pollutants.
What is meant by non-biodegradable pollutants ?

ANS :The pollutants which cannot be decomposed by microorganisms are called non-biodegradable pollutants.
Give examples of biodegradable pollutants.

ANS :Faecal matter, solid sewage waste, domestic waste, agricultural waste, paper, wood, clothes, etc. are biodegradable pollutants.
Give examples of non-biodegradable pollutants.

ANS :Pesticides like DDT, mercury, lead, aluminium, arsenic, plastics, etc. are examples of non-biodegradable pollutants.
What is Biomagnification ?

ANS :The accumulation of harmful non-biodegradable substances in the bodies of organisms through the foodchains and biogeochemical cycle is called Biomagnification.
Demand of what increases due to population explosion ?

ANS :Demand of space and food increases due to population explosion.
What is conservation of environment ?

ANS :Conservation of environment means such activities which provide individual or commercial benefits by preventing excessive use leading to environmental damage.
Mention the effects due to depletion of ozone layer.

ANS :Increase in ultraviolet radiation reaching earth due to depletion of ozone layer causes skin cancer, damage to eyes and damage to immune system.
What work has been done by NEERI for water pollution ?

ANS :NEERI has developed Oxygen Pond method for the treatment of industrial effluents and sewage.

ANS :

HEREDITY AND EVOLUTION - III : LONG ANSWERS

2008-08-19T00:28:00.000-07:00

GIVE ANSWER IN DETAIL

*INDEX-TOPIC SEARCH

Explain : Heredity and variation.
ANS :
HEREDITY :

Transmission of characters from parents to offsprings is known as heredity.
Fertilised egg or zygote carries hereditary information.
The zygote develops into a particular type of offspring only.
Thus, eggs laid by a sparrow hatch into sparrows and a dog reproduces to give birth to pups only.

VARIATION :

Variation means some individual diversity in the organism of one generation from that of the parental generation.
Variation passes from generation to generation.
In sexual reproduction, both similarities and variation are clearly observed among the offsprings of same parents.
Due to variation, any two persons rarely show complete similarity.

Explain : Mendel's concept of heredity.
ANS :

Mendel proposed that for regulation of every character in an organism there is a pair of factors.
During Mendel's time, nothing was known about chromosomes and DNA.
T.Boveri and W.S.Sutton proved that a gene is a part of chromosome.
Thus, Mendel indicated the path of transmission of factors from parental generation to offsprings through gamates.
Both Mendelian factors(genes) as well as chromosomes are present in pairs. They get separated from each other during meiosis when a haploid(n) gamate is formed.
During fertilisation, gamates fuse to form a zygote(2n) carrying characters which later on get transmitted to the offspring.

Write a note on sex determination and chromosomes OR Explain the role of chromosomes in sex determination.
ANS :

The phenomenon determining whether the developing embryo will be a male or a female is known as sex determination.
During the investigation on grasshoppers, one additional unpaired chromosome was observed in the male. This additional chromosome is called X-body and is known as sex chromosome since it is associated with sex determination.
The second sex chromosome is called X-chromosome if it is similar to the previous one and is called Y-chromosome if it differs from the X-chromosome.
In humans, the female has 2A + XX chromosomes and all the ova are A + X type.
The human male has 2A + XY chromosomes. This leads to 50% sperms of A + X type and 50% of A + Y type.
The fertilisation of an ovum by a sperm of A + X type produces a female whereas the fertilisation of an ovum by a sperm of A + Y type produces a male.
In some species, like turtle Chrysema Picta and lizard Agama agama, the sex determination is regulated by environmental factors.

What is biological evolution ? Mention the evidences supporting evolution and different theories of evolution.
ANS :

The sequential and well-organised process of gradual structural changes in species is called biological(organic) evolution.
Evidences of comparative anatomy, comparative embryology, vestigial organs, fossils, connecting links, physiology and taxonomy support biological evolution.
The various theories of evolution are :

Lamarck's theory of inheritance of acquired characters.
August Weismann's Germplasm theory.
Darwin's theory of Natural Selection.
Hugo De Vries' Mutation theory.

Explain : Chromosome is the physical basis of heredity.
ANS :

The discovery of the process of sexual reproduction involving gamates established the concept of transmission of genetic material.
Mendel proposed that there is a pair of factors for regulation of every character though during his time little was known about chromosomes and DNA.
T.Boveri and W.S.Sutton experimentally proved that gene is a part of chromosomes.
Mendelian factors(genes) as well as chromosomes are found in pairs but they get separated during meiosis forming haploid(n) gamates.
During fertilisation, gamates fuse to form zygote(2n) in which the characters are stored and transmitted to the offspring.
It was proved that the genes are located on chromosomes and the number of chromosomes is fewer than that of genes because the number of characters in an organism is very large. Thus, there are 23 pairs of chromosomes in human being but the total number of genes present on them is about 30,000 to 40,000.
It has been established that gene is a segment of a large molecule called DNA(DeoxyriboNucleic Acid).
DNA is the important component for the expression of genetic information from one generation to the other. Every chromosome possesses one molecule of DNA.
In some viruses, RNA(RiboNucleic Acid) is the genetic material. Such viruses are called retrovirus. The virus causing AIDS in human beings is a retrovirus.
Thus, chromosome is the physical basis of heredity.

Describe the structure of chromosome.
ANS :

Chromosomes are carriers of genes.
Chromosomes can be identified by staining.
In prokaryotes only one chromosome occurs whereas in eukaryotes many chromosomes occur in pair.
The paired structure of chromosomes is known as diploid(2n) and is seen in somatic cells. They are called homologous chromosomes as both the chromosomes of a pair are exactly similar.
The number of diploid chromosomes is fixed for a species.
In reproductive cells the chromosomes are haploid(n), i.e. they are half in number.
During cell division(metaphase), different chromosomes get separated from each other and their morphological study becomes possible.
A group of minimum two chromatids forms one chromosome.
The diameter of each chromatid is 60 A°.
Chromatids are joined with each other by a dark region called centromere or primary constriction. Some chromosomes have additional secondary constriction.
Variation can be seen in position and number of centromere.
The length of chromosomes is 0.2 - 5.0μ (micron) andtheir diameter ranges from 0.2 - 2.0μ.

Write a note on types of chromosomes.
ANS :

Chromosomes are classified depending on the position of the centromere.
There are four types : (i)Metacntric (ii)Sub-metacentric (iii)Acrocentric (iv)Telocentric.
Metacentric :

The centromere is present exactly in the centre.
All four arms of chromatids are equal in length.

Sub-metacentric :

The centromere is situated slightly away from the centre.
The two arms of chromatids on one side are long and the other two arms are short.

Acrocentric :

The centromere is located far from the centre near one end.
The two arms of chromatids on one side are very long and the other two arms are very short.
In some chromosomes, a small filamentous structure possessing a round tip is present on the distal end of short arms. This part is known as satellite.
A short filament called nucleolar organiser region connects satellite with the short arm.

Telocentric :

The centromere is situated at the tip of the chromosome.
The two arms are located only on one side.

Describe Watson-Crick model for structure of DNA.
ANS ::

In 1953, Watson and Crick proposed a model showing molecular structure of DNA.
In the molecule of DNA two polynucleotide chains run in antiparallel directions and twist around each other to form a spiral helical structure.
One nucleotide is linked with another nucleotide by a phospho-diaster bond.
In the chain, sugar and phosphate are linked with their nitrogenous bases.
Purine type nitrogenous base of one nucleotide links with pyrimidine type of nitrogenous base by weak hydrogen bonds.
Adenine(A) links with Thymine(T) by two weak hydrogen bonds whereas Guanine(G) links with Cytosine(C) by three weak hydrogen bonds. Such pairing is known as complimentary pairing.
The purine to pyrimidine ratio in each DNA molecule is always 1 : 1.
The length of one helix is 34 A° and each helix possesses 10 nitrogenous base pairs.
The distance between two adjacent nucleotides is 3.4 A° and the distance between two opposite chains is 20 A°.

Explain different evidences supporting biological evolution.
ANS ::

Comparative anatomy, comparative embryology, vestigial organs and fossils are major evidences supporting biological evolution.
COMPARATIVE ANATOMY :

A number of common features of different kinds of organisms favour evolution.
Homologous organs like forelimb of humans, fins of fishes, wings of birds, limb of frog and forelimb of lizard perform different functions but show structural similarities.
All these organs might have evolved from a common ancestor from which these organisms have evolved.
Analogous organs like wings of birds and wings of insects perform same function of flying but their origins differ. Wings of birds are modifications of forelimb but wings of insects are ectodermal derivatives(i.e they have originated from skin).

COMPARATIVE EMBRYOLOGY :

Embryology provides strong evidence of evolution for the origin of different organisms.
During the early stage of development, the embryos of different vertebrates show similarities.
Later, their development results in clearly visible differences.
This is an evidence of the fact that the vertebrates have a common ancestor and origin.
Based on this fact Ernst Hackel proposed the 'Recapitulation Theory' which states that "Ontogeny recapitulates phylogeny".

VESTIGIAL ORGANS :

Morphological studies have identified some organs which have lost their functions. These organs might have been functional in their ancestors. Such organs are called vestigial organs.
Vermiform appendix associated with large intestine is a vestigial organ in humans but it is functional in herbivores like rabbit.
Nictitating membrane of eye is a vestigial organ in humans but it is functional in birds and gives protection to the eyes.
Thus, vestigial organs support evolution.

FOSSILS :

Fossils provide some evidence to support evolution.
Fossils of Archaopteryx(now extinct) show that it looked like a bird but it had maximum reptilian characters. This indicates that birds have evolved from reptiles.

ANS :

HEREDITY AND EVOLUTION - II : BRIEF ANSWERS

2008-08-17T11:30:00.000-07:00

ANSWER IN BRIEF

*INDEX-TOPIC SEARCH

Explain : Heredity.
ANS:

Transmission of characters from parents to offsprings is known as heredity.
Fertilised egg or zygote carries hereditary information.
The zygote develops into a particular type of offspring only.
Thus, eggs laid by a sparrow hatch into sparrows and a dog reproduces to give birth to pups only.

Explain : Variation.
ANS:

Variation means some individual diversity in the organism of one generation from that of the parental generation.
Variation passes from generation to generation.
In sexual reproduction, both similarities and variation are clearly observed among the offsprings of same parents.
Due to variation, any two persons rarely show complete similarity.

Explain : The number of chromosomes is fewer than the number of genes.
ANS:

Genes are located on chromosomes.
Genes are responsible for specific characters of an organism.
The number of chromosomes in an organism is small but the number of characters of an individual organism is very large.
For example, there are 23 pairs of chromosomes in a human cell but the number of characters is very large requiring a large number of genes(30,000 to 40,000).
Thus, the number of chromosomes is fewer than that of genes.

Explain : Mutation.
ANS:

Gene is a segment of DNA and is a unit of inheritance.
The nature of a gene is maintained generation after generation but sometimes it undergoes sudden inheritable changes known as mutation.
Mutation is one of the reasons of variation among individuals and species.

Describe the role of environmental factors in sex determination.
ANS:

In some species, the sex determination is regulated by environmental factors.
For example, in turtle Chrysema Picta, high incubation temperature results into development of a female.
In a lizard, Agama agama, high incubation temperature results into development of a male.

Mention various theories of evolution.
ANS:

Lamarck's theory of Inheritance of acquired characters.
August Weismann's Germplasm theory.
Darwin's theory of Natural Selection.
Hugo De Vries' Mutation theory.

Write a few points on Darwin's theory of Natural Selection.
ANS:

Darwin's theory of Natural Selection describes biological evolution.
It explains how evolution takes place with the help of variation.
It fails to explain how variation occurs.

Explain : Homologous organs with example.
ANS:

The organs showing similarities in origin but performing different functions are called homologous organs.
Forelimbs of human beings, fins of fishes, wings of birds, limbs of frog and forelimbs of lizard have structural similarities due to same origin but they perform different functions.

Explain : Analogous organs with example.
ANS:

The organs showing different origin but performing the same functions are called analogous organs.
For example, both birds and insects use wings to fly(same function) but their origins are different. The wings of birds are modifications of forelimbs whereas the wings of insects are ectodermal derivatives(i.e. they have originated from skin).

Write a note on components of nucleotides.
ANS:

DNA is a macromolecule made up of a large number of nucleotides.
A nucleotide is made up of three components :

Pentose sugar(deoxyribose sugar)
Phosphate group(H₃PO₄)
Nitrogenous base
The nitrogenous bases are of two types :
Purines
Pyrimidines
Adenine(A) and Guanine(G) are purines whereas Cytosine(C) and Thymine(T) are pyrimidines.

ANS:

HEREDITY AND EVOLUTION - I : MCQs & SHORT ANSWERS

2008-08-15T10:38:00.000-07:00

*INDEX-TOPIC SEARCH

MULTIPLE-CHOICE QUESTIONS

SELECT THE CORRECT ALTERNATIVE:

Variation is observed in...

asexual reproduction
sexual reproduction
both asexual reproduction and sexual reproduction
neither of them

The number of genes is______ the number of chromosomes.

same as
less than
more than
less than or equal to

In human being ______ pairs of chromosomes are present.

23
46
30,000
40,000

The number of genes in human being is about...

23
46
1,000-2,000
30,000 to 40,000

Every chromosome possesses ______ molecule/s of DNA.

23
4
2
1

Which of the following is true ?

Chromopsomes are located on genes.
Chromosomes are part of a chromatid.
Chromotids are part of a chromosome.
Prokaryotes have paired chromosomes.

What is the diameter of a chromatid ?

40 A°
50 A°
60 A°
70 A°

The chromatids are joined to each other by...

chromosome
centromere
gene
DNA

The length of a chromosome is...

0.2-0.5μ
60 A°
60μ
34 A°

The diameter of a chromosome is...

0.2-0.5μ
0.2-2.0μ
60 A°
34 A°

A satellite structure is found in ______ chromosomes.

metacentric
sub-metacentric
acrocentric
telocentric

The centromere is situated at the tip of ______ chromosome.

metacentric
sub-metacentric
acrocentric
telocentric

Which of the following is not a nitrogenous base ?

Adenine
Guanine
Cytosine
Deoxyribose sugar

The molecule of DNA has ______ structure.

linear
cyclic
helical
hexagonal

Adenine links with thymine by ______ weak hydrogen bonds in DNA.

one
two
three
four

Guanine links with cytosine by ______ weak hydrogen bonds in DNA.

one
two
three
four

In a DNA molecule adenine links with ______.

adenine
guanine
cytosine
thymine

Each DNA molecule contains purine and pyrimidine in the ratio ______.

1 : 1
1 : 2
2 : 1
2 : 3

The cells in human female have chromosomes of the type ______.

A + X
A + Y
2A + XX
2A + XY

The cells in human male have chromosomes of the type ______.

A + X
A + Y
2A + XX
2A + XY

The ovum produced by a human female is ______ type.

A + X
A + Y
2A + XX
2A + XY

If the sperm having ______ chromosome fertilises an ovum then ______ is produced.

X, male
Y, female
X, female
XY, female

The principle of inheritance of acquired characters was given by...

Lamarck
Weismann
Darwin
Hugo De Vries

______ gave Germplasm Theory.

Lamarck
Weismann
Darwin
Hugo De Vries

Mutation theory was described by ______.

Lamarck
Hugo De Vries
Darwin
Weismann

Fossils of ______ provide evidence of evolutionas the connecting link between birds and reptiles.

Dinosaurs
Lizard
Archeopteryx
Ostrich

______ gives detailed information of variation and evolution.

Lamarckism
Modern synthetic theory
Recapitulation theory
Darwinism

The process of inheritance of characters in living beings is called...

heredity
evolution
variation
migration

Individual variation means...

heredity
variation
evolution
similarities

The branch of biology related with heredity and variation is called...

Genetics
Evolution
Taxonomy
Livinglogy

Boveri and Sutton proved that...

Factor is responsible for information of heredity.
Variation is inherited generation to generation.
Chromosomes are transported by gametes.
Gene is a part of a chromosome.

The number of chromosomes in comparison to the number of genes is...

less
more
equal
more or equal

The unit of expression of genetic information from one generation to another generation is...

DNA
RNA
both DNA & RNA
blood

An example of retrovirus is...

the virus responsible for AIDS
TMV
bacteriophage
RIV

Generally, the gametes, according to the number of chromosomes, are...

haploid
diploid
triploid
none of three

In which type of chromosome is the centromere displaced slightly from the center ?

Metacentric
Sub-metacentric
Acrocentric
Telocentric

Which type of nitrogen base are Adenine and Thymine ?

purine and pyrimidine
pyrimidine and purine
purine and purine
pyrimidine and pyrimidine

The extra chromosome found in male insect is called...

X-body
Y-body
homologous
neutral

In which animal, the embryo develops into a male at high temperature ?

turtle
lizard
grasshopper
fish

Which principle was given by Darwin ?

Inheritance of acquired characters
Germplasm theory
Mutation theory
Theory of natural selection

SHORT QUESTIONS

ANSWER IN SHORT:

Define : Heredity.

ANS :Heredity is defined as 'the transmission of characters from parents to the off-springs'.
Give the meaning of variation from biological point of view.

ANS :From biological point of view, variation means some individual difference(diversity) in the organismof one generation from that of the parental generation.
What is Genetics ?

ANS :Genetics is the branch of biology which studies important aspects of heredity and variation.
What did Mendel propose ?

ANS :Mendel proposed that for regulation of every character(in an organism) there is a pair of factors.
What happens when a cross is made between two pea plants ?

ANS :When a cross is made between two pea plnats showing different characters, only one character is seen in the offsprings but the successive generations show both characters.
Who showed that gene is a part of chromosome ?

ANS :T.Boveri and W.S. Sutton showed that gene is a part of chromosome.
Where are genes located ?

ANS :Genes are located on chromosomes.
Of what is a gene the segment ?

ANS :A gene is a segment of DNA(deoxyribonucleic acid).
Who established the DNA as a component for expression of genetic information from one generation to the other ?

ANS :Griffin, Avery, McLeod and McCarty established the DNA as a component for expression of genetic information from one generation to the other.
What is meant by homologous chromosomes ?

ANS :Homologous chromosomes are chromosomes occurring in pair and the members of a pair of chromosomes are exactly identical.
What is the difference between prokaryotic and eukaryotic chromosomes ?

ANS : In prokaryotes only one chromosome occurs whereas in eukaryotes many chromosomes occur in pairs.
What is the difference in number of chromosomes of somatic cells and reproductive cells ?

ANS :The number of chromosomes in reproductive cells is half(haploid) of that in somatic cells(diploid).
When do chromosomes get separated from each other ?

ANS :Chromosomes get separated from each other during metaphase of cell division.
Why can chromosomes be identified easily during metaphase ?

ANS :Chromosomes can be identified easily during metaphase because they get separated from each other.
What is centromere (primary constriction) ?

ANS :In a chromosome, the dark region which connectes two individual chromatids is known as centromere (primary constriction).
How are chromosomes classified ?

ANS :Chromosomes are classified depending on the position of the centromere.
Mention the types of chromosomes.

ANS :Metacentric, submetacentric, acrocentric and telocentric are the types of chromosomes.
What is nucleolar organisation region ?

ANS :A short filament connecting the satellite with the arm of an acrocentric chromosome is called nucleolar organisation region.
What is the full form of DNA ?

ANS :The full form of DNA is DeoxyriboNucleic acid.
What is DNA ?

ANS :DNA is a macromolecule in which a large number of nucleotide units is present.
Why is DNA known as polynucleotide ?

ANS :DNA is known as polynucleotide as it is a macromolecule consisting of a large number of nucleotide units.
Mention the components of a DNA nucleotide.

ANS :The components of a DNA nucleotide are : (1)Pentose sugar(deoxyribose sugar),(2)Phosphate group(H₃PO₄) and (3)Nitrogenous base.
Mention the types of nitrogenous base in DNA.

ANS :Purines and pyrimidines are the types of nitrogenous base in DNA.
Mention the purines present in DNA.

ANS :Adenine and Guanine are the purines present in DNA.
Mention the pyrimidines present in DNA.

ANS :Cytosine and Thymine are the pyrimidines present in DNA.
What is complimentary pairing ?

ANS :The linking of a purine type nitrogenous base with a pyrimidine type nitrogenous base by weak hydrogen bonds in a DNA molecule is called complimentary pairing.
What is the length of each helix in a DNA molecule ?

ANS :The length of each helix in a DNA molecule is 34 A°.
How many nitrogenous base pairs are present in one helix of DNA ?

ANS :10 nitrogenous base pairs are present in one helix of DNA.
What is the distance between two adjacent nucleotides in a DNA molecule ?

ANS :The distance between two adjacent nucleotides in a DNA molecule is 3.4 A°.
What is the distance between two opposite chains of a DNA helix ?

ANS :The distance between two opposite chains of a DNA helix is 20A°.
What is the biological name of the fruit fly ?

ANS :Drosophila melanogaster is the biological name of the fruit fly.
What is mutation ?

ANS :A sudden inheritable change in the nature of a gene is called mutation.
Mutation is one of the reasons of variation. True or false ?

ANS : TRUE
What is the effect of high incubation temperature in determining sex in a turtle, chrysema picta ?

ANS :The high incubation temperature in a turtle, chrysema picta, results in the development of a female.
What is the effect of high incubation temperature in determining sex in a lizard, agama agama ?

ANS :The high incubation temperature in a lizard, agama agama results in the development of a male.
Give an example of a plant showing sex determination.

ANS :Coccinia indica is a plant showing sex determination.
What are the two basic factors of evolution ?

ANS :Variation and heredity are the two basic factors of evolution.
How is a new species evolved ?

ANS :A new species is evolved during evolution process due to small changes in the heredity of one generation which gives rise to a new generation with different characters.
Mention the types of evidence that support the biological evolution.

ANS :Evidences of comparative anatomy, comparative embryology, vestigial organs, fossils, connecting links, physiology and taxonomy support biological evolution.
Which theory of evolution did Darwin give ?

ANS :Darwin gave the Theory of Natural Selection.
Mention the limitation of Darwinism.

ANS :Darwinism explains evolution with the help of variation but it does not explain how variation occurs.
What are homologous organs ?

ANS :The organs showing similarities in origin but performing different functions are called homologous organs.
What are analogous organs ?

ANS :The organs different origin but performing same functions are called analogous organs.
Who proposed recapitulation theory ?

ANS :Ernst Hackel proposed recapitulation theory.
What does recapitulation theory state ?

ANS :Recapitulation theory states that 'Ontogeny recapitulates phylogeny'.
What are vestigial organs ?

ANS :Those organs found in an organism which are not functional but which might have been functional in ancestors are called vestigial organs.
What do you study in Genetics ?

ANS :We study important aspects of heredity and variation in Genetics.
What is satellite(in a chromosome)?

ANS :Satellite is around structure at the tip of the filament on the distal end of the short arm of an acrocentric chromosome.
What is retrovirus ? Give an example.

ANS :Retrovirus is a virus with RNA as hereditary material. The virus causing AIDS in humans is a retrovirus.
What is organic(biological) evolution ?

ANS :A natural process of structural sequential transformation of species which is slow but progressive is called organic(biological) evolution. OR The structural and well-organised process of gradual changes in species is called organic(biological) evolution.

ANS :

ANS :

REPRODUCTION IN ORGANISMS - III : LONG ANSWERS

2008-07-24T23:40:00.000-07:00

GIVE ANSWER IN DETAIL

*INDEX-TOPIC SEARCH

Describe fission as a method of reproduction.

ANS :Fission occurs in unicellular organisms. Binary fission and multiple fission are its two types.

BINARY FISSION :

An organism produces two unicellular organisms identical to the parent cell through mitotic division.
Amoeba, paramoecium, etc. reproduce by binary fission.

MULTIPLE FISSION :

Under certain circumstances, the nucleus of a cell divides several times within the cell forming many nuclei.
Each nucleus is then surrounded by cytoplasm to form a separate unit.
All these newly formed cells then come out of the mother cell(parent cell) by breaking the wall and behave as a new organism.
Plasmodium, amoeba, paramoecium, etc. exhibit such reproductive event.

Describe budding as a method of reproduction.

ANS :

Budding is observed in both unicellular and multicellular organisms.
In unicellular organisms, some part of the body swells out at one point and developes into a 'bud' due to the formation of nucleus and cytoplasm within it. This bud then separates from the parent cell and behaves as an independent organism. Sometimes the buds form a chain before being separated. Example : yeast.
In multicellular organisms like hydra, a part of its cylindrical body swells and develops into a bud. This bud then grows and separates from the mother's body to develop as an independent daughter animal.

Describe spore formation as a method of reproduction.

ANS :

Spore formation is the most common method of asexual reproduction in majority of bacteria and fungi.
During spore formation, a structure called sporangium develops from fungal hypha which is a filamentous structure.
The nucleus in sporangium divides several times and forms many nuclei.
Each nucleus gets surrounded by cytoplasm and forms small unicellular structure called spore.
When sporangium bursts, the spores spread into the surrounding environment and germinate into new hypha forming mycellium which behaves as new organism.
Mucor and Rhizopus reproduce by this method.

Describe regeneration as a method of reproduction.

ANS :

Regeneration is the ability of an organism to reproduce the lost parts of its body.
When some body part of an organism breaks suddenly, a new part similar to the lost (broken) part is created at the point of breaking after some time.
All broken parts thus develop into new organisms.
Hydra, planaria, sponge and starfish reproduce by regeneration.
Some filamentous algae increase their number by this method. Algae filaments break frequently and each broken piece develops into independent algae. This is called fragmentation.

Describe role of sex hormones in humans.

ANS :

Once a male reaches puberty, testes start producing sex hormone testosterone. Similarly, in females, ovaries start producing sex hormones estrogen and progesterone.
These hormones play an important role in the regulation of the processes of spermatogenesis (in male) and oogenesis (in female).
Sex hormones are also responsible for the structural development, maintenance and functions of accessory sex organs.
They induce secondary sexual characters at proper age.
The secondary sexual characters in male include : growth of hair on face, chest and other body parts; change in voice, aggressive behaviour and mental agitation.
Those in female include : changes in face and body, development of mammary glands, change in the pitch of voice, vigilant behaviour and sentimental approach.

What is the difference between menstruation and menopause ?

ANS :When a woman (girl) attains puberty, her reproductive system becomes functional. As a result the ovary starts releasing ovum and this phenomenon is repeated after a definite period as a cycle. When an ovum is released the uterine wall gets ready for the implantation of fertilised ovum (zygote). If the ovum is not fertilised within certain period, it gets destroyed and the uterine wall disintegrates resulting in the breaking of blood vessels. The disintegrated tissue along with blood flows out through vagina. This flow of blood continues for about 3-5 days and is called menstruation.

Menstruation, as a part of sexual cycle, starts at the age of about 10-12 years and its commencement indicates that the reproductive system of the woman has become active. The reproductive system then remains active up to the age of about 45-50 years and then becomes non-functional. The sexual cycle stops and menstruation ceases. This is called menopause. Thus, menopause marks the end of reproductive period of a woman.

Describe vegetative propagation in detail.

ANS :

Development of a new plant from root, stem or leaf is called vegetative propagation.
Some higher plants exhibit this method of reproduction.
Examples : (i)Development of buds from the root of sweet potato.(ii)Development of buds on potato tuber.(iii)Development of buds on the margin of bryophyllum leaf.
Besides natural method, artificial vegetative propagation is also used to increase production. Cutting, layering and grafting are commonly used methods of artificial vegetative propagation.

Describe various methods of artificial vegetative propagation.

ANS :

CUTTING :

In this method, a piece of root, stem, leaf or sometimes a bud is sown in soil which develops into a new plant.
The piece of the plant sown in the soil develops roots downwards in the soil and aerial organs in the external environment.
this method is useful for large scale production which is greatly economical and profitable.
Example : sugarcane, grapes, rose, phalsa.

LAYERING :

In this method, a branch of stem of a plant is bent towards the soil in such a way that some part of the branch remains inside the soil and its tip remains outside.
The part covered by the soil develops roots.
When this part is detached from the parent plant, it grows independently into a new daughter plant.
Example : Lemon, guaua, hibiscus, jasmine and bougainvillaea.
In plants like strawberry and raspberry, sometimes a branch comes into contact of the soil naturally and develops as a daughter plant after producing roots.

GRAFTING :

Grafting is a method in which two parts of different plants are joined together in such a way that they unite to grow as one plant.
A part of an adult (mature) plant is tied up with a unit of soft plant to get early flowering in the soft plant.
The portion of the plant having roots on which grafting is performed is called 'stock'.
The portion of the plant which is grafted on the other plant is called 'scion'.
By this method, desirable characteristics of different plants can be combined.
This method is very useful for plants whose seeds have long dormancy period and poor germination capacity.
Example : On the stock of lemon, a scion of lemon or orange can be grafted. This method is widely used to increase the production of mango.

Describe reproductive system in human male.

ANS :

A pair of testes is the main reproductive organ in human male.
Vas deferens and penis are the accessory reproductive organs.
Seminal vesicle, prostate gland and bulbourethral gland are the accessory reproductive glands.
The two testes lie in a muscular sac called scrotum outside the abdominal cavity in the region between legs.
The temperature in the scrotum is 3°C lower than that of the body. This temperature is suitable for the process of spermatogenesis.
The sperms produced in the testes are transported through vas deferens to the penis.
Sperms mix with the semen which is formed by the secretions of reproductive glands.
Semen provides movement to sperms so that they can reach the egg cell(ovum).
In male, urine and sperms get released through the same path called urinogenital path.

Describe reproductive system in human female.

ANS :

The main reproductive organ in human female is a pair of ovaries located in the abdominal cavity.
The reproductive system includes ovaries, fallopian tube (oviduct), uterus, cervix, vagina and vaginal opening.
Accessory reproductive organs include labia major, labia minor and clitoris.
Ovaries possess many ovarian follicles which become mature at puberty stage and form graffian follicle. Graffian follicle form the structure of ovum.
Generally, one ovarian follicle becomes active alternately and forms one ovum.
The free end of the oviduct towards ovary is fimbricated and funnel shaped. It is known as oviductal funnel.
The oviducts on both sides join in the middle to form inverted triangular shaped muscular sac called uterus. The mouth of uterus opens into vagina through narrow cervix.
Vagina opens outside the body through vaginal opening.
There is a separate urinary opening above the vaginal opening. Thus, in female, the urinary passage and genital passage are separate from each other.

Describe sexual cycle in human female.

ANS :

The sexual cycle in female starts at puberty stage when the development of ovum starts in ovary from ovarian follicle.
When the ovum develops (matures) up to a definite stage it is released by rupturing of ovarian follicle. This is called ovulation.
During first 13 days of cycle, development of ovum occurs and ovulation takes place on the 14th day. After ovulation, the ovum enters oviduct through oviductal funnel.
Simultaneously, the walls of uterus get ready for the implantation of embryo.
If fertilisation occurs, the implantation of embryo on the walls of uterus takes place and the process of supply of nutrition to embryo starts.
If fertilisation does not occur, the walls of uterus that got prepared for implantation in the form of blood-filled tissues start disintegrating.
This results in the breakdown of blood vessels and the broken uterine wall tissues come out through vagina along with blood. This is known as Menstruation.
Menstruation may last for 3-5 days during which abdominal pain is experienced.
Then the cycle is repeated. Generally menstruation cycle is repeated every 28-32 days.
The secretion of sex hormones at puberty stage is responsible for the commencement of menstrual cycle. With this the female attains the ability of conception.
The sexual cycle generally remains functional up to the age of 45-50 years. Then gradually the sexual cycle stops due to hormonal changes and menopause starts indicating the loss of the ability of conception.

Describe fertilisation and embryo development in humans.

ANS :

During the sexual cycle of a female ovulation occurs on the 14th day and the ovum enters the fallopian tube.
If copulation occurs during the period when the ovum is present in the oviduct, sperms released in semen try to reach the ovum with the help of the fluid substances present in semen.
If one of the sperms can reach the egg(ovum) in the oviduct, then fertilisation takes place.
If fertilisation occurs, then the walls of uterus start further developments.
The embryo(fertilised egg) reaches the walls of the uterus and gets implanted on the wall.
An umbilical cord develops from the embryo to the uterine wall and supplies nutrition to the embryo from mother's body.
For the protection of the developing embryo, a structure (amnion) filled with amniotic fluid develops.
The birth of the child takes place, usually, after 40 weeks or 280 days. (this is the time for the development of the embryo into a mature baby).
Duration from zygote formation till birth of the child is called embryo developing time.
When the development of the embryo is complete, a new born child comes out of the mother's body by breaking the amnion. This event is known as delivery.
The calculation of embryo development time starts from the first day of last menstrual cycle.
The normal weight of the foetus(at the time of birth) should be about 3-3.5 kg.

Write an explanatory note on population control.

ANS :

Growth of population is one of the biggest problems in the world. The population of India has crossed 1 billion mark and it needs serious attention . Also, frequent delivery can be dangerous to both the mother and the child as it results in ill health and the birth of a weak baby.
Keeping the growth rate of population limited by using some scientific devices is called population control.
Types of such devices include : (i) Birth-control tools (ii) Chemical devices (iii) Surgical devices.
Birth-control tools :
A condom used by males prevents the entry of semen into vagina during copulation.
A copper-T or a loop used by a female prevents implantation in uterus.
Chemical devices include birth-control pills containing hormones which prevent implantation.
Surgical methods :
In males, the vas deferens is cut and tied up to prevent the transport of sperms. The method is called Vasectomy.
In females, the oviduct is cut and tied up to prevent the transport of ovum. The method is called Tubectomy.
A doctor must be consulted before following any method of population control to avoid side effects.

Write a note on sexually transmitted diseases (STDs).

ANS :

Sexually transmitted diseases are infectious and some times they prove fatal.
The diseases occurring due to unsafe sexual intercourse are called Sexually Transmitted Diseases(STDs).
Such diseases are caused by virus, bacteria, fungi and protozoans.
Syphillis is caused by Treponema Palidium.
Gonorrhoea is caused by Neissena Gonorrhoea.
Symptoms of STDs :
Inflammation of the passage of urine.
Lesions on the skin of urinary tract and vagina.
Itching sensation in penis or vagina.
Lesions on genital passage.
STDs are curable by proper treatment, so a doctor must be consulted immediately without hesitation when any of the symptoms of STDs become visible.
AIDS can prove fatal. Research work is in progress to find out medicines to cure AIDS.
WHO has given several guidences to prevent the spread of STDs and to protect human race.
In India, NACO (National AIDS Control Organisation) and other NGOs (Non-Government Organisations) are functioning to create awareness about STDs.
Individual Care :

One should keep awareness about the cleanliness of the reproductive organs.
There must be limit in developing friendship with opposite sex.
Use of birth-control tools during intercourse can prevent such diseases.
The best one is to learn to keep control on sexual desires.
Morality must be imposed as religious practice.

ANS :

REPRODUCTION IN ORGANISMS - II : BRIEF ANSWERS

2008-07-20T23:27:00.000-07:00

ANSWER IN BRIEF

*INDEX-TOPIC SEARCH

What is reproduction ? Mention its importance.
ANS:
The process by which organisms produce new organisms similar to them is known as reproduction.

The importance of reproduction is :

It maintains the existence of each species.
It transfers hereditary characteristics to the next generation.
It brings concomitant changes in evolutionary events.

What is asexual reproduction ? Mention its types(methods).
ANS:The process of reproduction in which any somatic part of the body of a single organism develops into a new organism is called asexual reproduction.

Its types are :

fission
budding
spore formation
regeneration
vegetative propagation

What is vegetative propagation ? Mention its different methods.
ANS:Development of a new plant from the root, stem or leaf is called vegetative propagation.

The different methods of vegetative propagation are :

Cutting
Layering
Grafting

Write a note on fission as a method of reproduction.
ANS:

Fission occurs in unicellular organisms.
It is a method of asexual reproduction.
Binary fission and multiple fission are its two types.
Amoeba, paramoecium,plasmodium,etc. reproduce by fission.

Explain : Binary fission.
ANS:

It is a method of asexual reproduction occurring in unicellular organism.
An organism produces two unicellular organisms identical to the parent cell through mitotic division.
Amoeba, paramoecium,etc. reproduce by binary fission.

Write a note on puberty.
ANS:

Puberty is the stage in the life of a human being when the reproductive organs show gradual change in structure and they become functional.
A boy attains puberty at the age of 13-14 years whereas a girl attains it at the age of 10-12 years.
During puberty,testes in male start producing sperms and sex hormone testosterone.
Similarly, ovaries in female start producing ovum and sex hormones estrogen and progesterone.

Mention accessory reproductive glands and their function in human male.
ANS:Seminal vesicle,prostate gland and bulbourethral gland are the accessory reproductive glands in human male. The secretions of these glands form semen which provides movement to sperms so that they can reach the egg cell easily.

Mention the requirements of fertilisation of an ovum.
ANS:

Ovulation must have occurred and hence the ovum must be present in the oviduct.
Copulation must occur before the ovum gets destroyed.
A sperm must reach the ovum to fertilise it.

Why is population control needed ?
ANS:Population control is needed to control population growth which is the biggest problem in the world. Also, frequent deliveries can be dangerous for the health of a female and they can result in the birth of a weak(unhealthy) child.

Mention symptoms of STDs (Sexually Transmitted Diseases).
ANS:

Inflammation of urinary tract and hence pain at the time of passing urine.
Lesions on skin of the urinary tract.
Itching sensation in penis or vagina.
Lesions on genital passage.

What individual care should one take to prevent STDs ?
ANS:

One should keep awareness about the cleanliness of reproductive organs.
There must be limit in developing friendship with opposite sex.
One should use birth-control tools during intercourse to prevent such diseases.
One should learn to keep control on sexual desires.
Morality must be imposed as a religious practice.

Distinguish between menarche and menopause.

ANS:

ANS:

REPRODUCTION IN ORGANISMS - I : MCQs & SHORT ANSWERS

2007-07-29T04:56:00.000-07:00

*INDEX-TOPIC SEARCH

MULTIPLE-CHOICE QUESTIONS

SELECT THE CORRECT ALTERNATIVE:

Which of the following is not a unicellular organism ?

Amoeba
Paramoecium
Hydra
Yeast

Which of the following shows budding ?

Yeast
Amoeba
Paramoecium
Plasmodium

Which of the following shows multiple fission ?

Hydra
Yeast
Spirogyra
Plasmodium

Which is the most common method of reproduction in majority of fungi and bacteria ?

Binary fission
Multiple fission
Budding
Spore formation

Which of the following shows spore formation ?

Amoeba
Mucor
Plasmodium
Paramoecium

Regeneration is observed in ______.

Amoeba
Planaria
Spirogyra
Yeast

Which of the following does not show regeneration ?

Mucor
Planaria
Sponges
Starfish

Which of the following is not an artificial method of vegetative propagation ?

Cutting
Layering
Grafting
Hybridization

Testes produce ______ hormone.

Estrogen
Testosterone
Progesterone
Both estrogen and testosterone

Which of the following is not produced in the ovary ?

Ovum
Estrogen
Progesterone
Testosterone

The main reproductive organ of human male is ______.

a pair of testes
vas deferens
urethra
penis

The main female reproductive organ is ______.

Fallopian tubes
uterus
vagina
a pair of ovaries

The first phase of the sexual cycle in human female is called ______.

ovulation
implantation
menstruation
follicle phase

Menstrual flow(menstruation) lasts for about ______ days.

2 - 3
3 - 5
5 - 7
14

In a normal healthy woman, menstruation occurs every ______ days.

14
28 - 32
21 - 24
270

What marks the beginning of the reproductive life of a woman ?

ovulation
menopause
menarche
fertilisation

What is formed after fertilisation ?

A sperm
An ovum
A zygote
A gamete

Where does fertilisation take place ?

vagina
cervix
Fallopian tube
uterus

What should be the normal weight of a fully matured foetus (child at birth)?

2.5 - 3.0 pounds
2.5 - 3.0 kg
3.0 - 3.5 pounds
3.0 - 3.5 kg

______ prevents ovulation.

Testosterone
Progesterone
Estrogen
Contraception

Which of the following shows budding ?

Hydra
Amoeba
Paramoecium
Spirogyra

Several new individuals are produced.

Binary fission
Multiple fission
Both binary fission and multiple fission
Fertilisation

In grafting the plant rooted in the soil is called ______.

stock
sucker
scion
rhizome

Which of the following plants shows vegetative propagation ?

Wheat
Radish
Sunflower
Bryophyllum

Testes in human male are located in ______.

abdominal cavity
vas deferens
scrotum
penis

In the process of sexual reproduction ______.

only males are needed
both male and female are needed
only females are needed
only mitosis is involved

The process of release of an egg from the ovary is called ______.

reproduction
ovulation
menstruation
fertilisation

______ takes place in a woman after 45 - 50 years.

Menstruation
Ovulation
Menopause
Lactation

The period taken for one complete menstrual cycle is ______.

31 days
32 - 35 days
28 - 32 days
22 - 25 days

The development of foetus inside the uterus till birth is called ______.

gestation
parturition
lactation
fertilization

The unicellular fungus which shows bud formation is ______.

mucor
yeast
amoeba
none of these

The animal which shows regeneration is ______.

amoeba
paramoecium
hydra
rhizopus

The method by which desired characters of two plants can be combined is ______.

cutting
layering
budding
grafting

The disease caused by treponema palidium is ______.

AIDS
syphillis
gonorrhoea
hepatitis

Yeast reproduces by...

budding
fission
regeneration
spore formation

A chain of buds is formed in...

hydra
yeast
mucor
plasmodium

Vegetative propagation is observed in...

yeast
hydra
mucor
bryophyllum

______ is useful where seeds have long dormancy period and poor germination capacity.

Cutting
Layering
Grafting
Regeneration

______ is a very useful method for developing garden.

Cutting
Layering
Grafting
Budding

The stage at which there is a gradual change in structure of reproductive organs in human male and female is called...

spermatogenesis
oogenesis
menarche
puberty

The temperature in the scrotum is about ______ deg C lower than the body temperature.

2
3
5
6

Which of the following is not a part of reproductive system in human male ?

Testis
Seminal vesicle
Clitoris
vas deferens

Which of the following is not a part of reproductive system in human female ?

Ovary
Cervix
Vagina
vas deferens

The sexual cycle in human female starts at...

birth
the age of 45
the age of 28
puberty stage

Ovulation occurs on the ______ day of the sexual cycle.

14th
20th
28th
any

The sexual cycle in human female remains active(functional), generally, up to the age of...

30 years
35-40 years
45-50 years
55-60 years

The 14th day of sexual cycle in human female is important because on that day...

ovulation occurs
she becomes pregnant
menstrual flow starts
she gives birth to a child

______ fertilises an ovum in a female's body.

Blood
Testosterone
A sperm
Seminal fluid

The nutritional requirements of an embryo are maintained through...

ovarian follicle
oviduct
mouth
umbilical cord

In humans, generally, the birth takes place after ______ of embryo development.

14 weeks
28 weeks
40 weeks
280 weeks

The calculation of embryo development (age of embryo) starts from...

the first day of last menstrual cycle
the first day of first menstrual cycle
the last day of first menstrual cycle
the last day of last menstrual cycle

Which of the following is a chemical device of birth control ?

Copper-T
Condum
Birth-control pills
Loop

Where are the testes of human male located ?

In abdominal cavity
In vas deferens
In scrotum
In penis

The process of release of egg from ovary is called...

reproduction
ovulation
menstruation
menopause

The period after 45-50 years in woman is known as...

menstruation
gestation
menopause
lactation

How many days are there in one menstrual cycle ?

31
32-35
28-32
22-40

The period from the formation of embryo to birth is known as...

gestation
parturition
lactation
fertilisation

Every organism produces another identical organism. This event is known as...

growth
reproduction
alteration of generation
regeneration

The method by which the desired characters of two plants can be combined is...

cutting
layering
budding
grafting

During embryo development, the embryo is protected by...

amnion
placenta
umbilical cord
oviduct

ANSWERS TO MCQs:

(1) C (2) A (3) D (4) D (5) B (6) B (7) A (8) D (9) B (10) D (11) A (12) D (13) D (14) B (15) B (16) C (17) C (18) C (19) D (20) B (21) A (22) B (23) A (24) D (25) C (26) B (27) B (28) C (29) C (30) A (31) B (32) C (33) D (34) B

SHORT QUESTIONS

ANSWER IN SHORT:

What is reproduction ?

ANS : The process by which the organisms produce new organisms similar to them is known as reproduction.

Why is reproduction essential ?

ANS : Reproduction is essential for the perpetuation of species and thereby life.

Mention the types of reproduction.

ANS : Asexual reproduction and sexual reproduction are the two types of reproduction.

What is asexual reproduction ?

ANS : Asexual reproduction is the method of reproduction involving only a single individual (organism),i.e. only one organism is needed for reproduction.

Mention different types of asexual reproduction.

ANS : (i) Fission (ii) Budding (iii) Spore Formation (iv) Regeneration (v) Vegetative propagation, etc are types of asexual reproduction.

Mention two types of reproduction by fission.

ANS : Binary fission and multiple fission are the two types of fission.

What is binary fission ?

ANS :When two independent adult organisms are formed after the division of the nucleus and the cytoplasm of one (mother) cell into two (daughter) cells, the process of reproduction is called binary fission.

Give examples of organisms showing binary fission.

ANS : Amoeba and paramoecium show binary fission.

What is multiple fission ?

ANS :When the nucleus of one (mother) cell divides several times into many (daughter) nuclei, each forming an individual organism, the process is called multiple fission.

Give examples of organisms showing multiple fission.

ANS : Plasmodium and amoeba show multiple fission.

What is budding ?

ANS : Budding is a process of reproduction in which a small protuberance (bud) appearing on an adult cell gradually grows bigger and then behaves as an independent organism after being detached from the (mother) cell.

Give examples of organisms showing budding.

ANS : Yeast and hydra show budding.

What is the similarity between hydra and yeast ?

ANS : both hydra and yeast exhibit budding as the method of reproduction.

Mention some organisms showing spore formation.

ANS : Mucor, rhizopus and penicillium show spore formation.

What is sporangium ?

ANS : Sporangium is a structure developing from fungal hypha and it contains a nucleus (spore) which divides several times forming a large number of spores which develop into new hyphae after falling on the ground.

What is regeneration ?

ANS : The ability of an organism to replace the lost parts of its body is called regeneration.

What is fragmentation ?

ANS : When an organism breaks into two or more pieces after being mature and then each piece grows as an individual organism, the process is known as fragmentation.

Give examples of organisms showing fragmentation.

ANS : Oscillatoria and spirogyra show fragmentation.

What is vegetative propagation ?

ANS : Vegetative propagation is a method of reproduction in which a new plant developes from a part of a root, stem or leaf.

Give examples of plants showing vegetative propagation.

ANS : Potato, sweet potato, bryophyllum, etc. show vegetative propagation.

Mention names of artificial methods of vegetative propagation.

ANS : Cutting, layering, grafting etc are artificial methods of vegetative propagation.

Give examples of some plants in which cutting is used as a method of vegetative propagation.

ANS : Cutting is used as a method of vegetative propagatin for sugarcane, grapes, rose, phalsa, etc.

Give examples of some plants in which layering is used as a method of vegetative propagation.

ANS : layering is used as a method of vegetative propagation for lemon. guaua, hibiscus, jasmine, bougainvillaea, etc.

What is grafting ?

ANS : Grafting is a method of vegetative propagation in which two parts of two different plants are joined together in a specific manner so that they unite to grow as one plant.

What is 'scion' ?

ANS : The portion of the plant which is grafted on other plant is called scion.

What is 'stock' ?

ANS : The plant on which grafting is performed is called stock.

In what circumstances is grafting a better method ?

ANS : Grafting is a better method for plants where seeds are having long dormancy period and poor germination capacity.

At which stage of life the reproductive system of human being becomes functional ? (write one word).

ANS : Puberty.

Mention the age of puberty in male and female human beings.

ANS : The age of puberty in human male is about 13-14 years and that in human female is about 10-12 years.

Mention the names of human gonads.

ANS : Testis (testes) in male and ovary in female are human gonads.

Name the sex hormone of human male.

ANS : Testosteron is the sex hormone of human male.

Which hormones are produced in ovary of human female ?

ANS : Estrogen and progesteron are produced in the ovary of human female.

Which are the two processes referred to as gametogenesis ?

ANS : Spermatogenesis and oogenesis are referred to as gametogenesis.

Mention the optimal temperature for spermatogenesis.

ANS : A temperature 3 °C lower than the body temperature is optimal for spermatogenesis.

What is urinogenital path ?

ANS : Urinogenital path is the common opening through which both urine and the sperms are released.

What is ovulation ?

ANS : The release of an ovum from the ovary by rupturing the ovarian follicle is called ovulation.

What is menstrual cycle ?

ANS : The cycle of events taking place in the ovaries and uterus every 28 days and marked by the flow of blood is called menstrual Cycle.

What is menarche ?

ANS : The commencement of menstruation at puberty in a woman is called menarche.

What is menopause ?

ANS : Menopause is the stage in a woman's life when menstrual flow and other related events stop.

What is fertilisation ?

ANS : The union of the male and female gametes resolting in the formation of zygote is called fertilisation.

Mention the type of fertilisation taking place in humans.

ANS : Internal fertilisation takes place in humans.

Mention the term used for male gamete.

ANS : Sperm.

What indicates that the fertilisation has taken place ?

ANS : The absence of menstrual flow at its regular interval indicates that the fertilisation has occured.

What is implantation ?

ANS : The close attachment of the embryo with the walls of uterus is called implantation.

What is placenta ?

ANS : A special tissue between the uterus wall and the embryo (foetus) that fulfils the nutritional, respiratory and excretory needs of the foetus from mother's body is called placenta.

What is the function of amniotic fluid ?

ANS : The function of amniotic fluid is to protect the foetus against temperature changes and mechanical shocks.

What is gestation ?

ANS : The development of the foetus inside the uterus till birth is called gestation.

What is the average duration of pregnancy (gestation period) in human beings ?

ANS : The average duration of pregnancy in human beings is about 280 days or 40 weeks.

What is parturition ?

ANS : The birth of a fully developed foetus after the completion of gestation period is called parturition.

What is family planning ?

ANS : Family planning is the adoption of various new techniques which prevent fertilisation or pregnancy.

What is Zero (Rhythm) method ?

ANS : Zero or Rhythm method is a natural method of contraception in which sexual intercourse is avoided 3 days before ovulation and 1 day after ovulation.

What is 'coitus interruptus' ?

ANS : Coitus interruptus is a natural method of contraception in which the penis is withdrawn from vagina before ejeculation (of semen).

Mention two natural methods of contraception.

ANS : (i)Zero (Rhythm) method (ii) Coitus interruptus.

What is the full form of IUCD ?

ANS : The full form of IUCD is IntraUterine Contraceptive Device.

What is a contraceptive ?

ANS : A device or a substance that prevents fertilisation during intercourse is called a contraceptive.

What is contraception ?

ANS : Contraception is a method of prevention of fertilisation of ovum (pregnancy).

What is vasectomy ?

ANS : Vasectomy is the process of surgical removal of a small portion of vas deferens of a male to prevent fertilisation.

What is tubectomy ?

ANS : Tubectomy is the process of surgically cutting and tying the Fallopian tube of a female to prevent fertilisation.

What is the full form of WHO ?

ANS : The full form of WHO is World Health Organisation.

Define 'health' according to WHO.

ANS : According to WHO, health is a state of complete physical, mental and social well being and not merely the absence of disease.

What are STDs ?

ANS : The infectious diseases which are spread from an infected person to a healthy person by sexual contact are called Sexually Transmitted Diseases (STDs).

What is gonorrhoea ?

ANS : Gonorrhoea is the inflammation of urinogenital tract causing burning sensation during urination.

Which organism causes gonorrhoea ? (Write the name only).

ANS : Neissena gonorrhoea.

What is syphillis ?

ANS : Syphillis is an STD in which there are lesions in the mucuos membrane urinogenital tract and ulcers on genitalia.

Which organism causes syphillis ?

ANS : Treponema palidium causes syphillis.

What is the full form of AIDS ?

ANS : The full form of AIDS is Acquired
Immuno-Deficiency Syndrome.

Which virus causes AIDS ?

ANS : HIV or Human Immuno-deficiency Virus causes AIDS.

Name two animals that can regenerate their lost body parts.

ANS : Planaria and starfish.

Which two sex hormones are produced by ovary in human female ?

ANS : Progesterone and estrogen are produced by ovary in human female.

Name main sex organs in humans.

ANS : Apair of testes in male and a pair of ovary in female are the main sex organs in humans.

What is an ovary ?

ANS : An ovary is the main sex organ in human female which exists in pair and releases an every month to the fallopian tube.

Give the location and function of placenta.

ANS : Placenta is located between the wall of the uterus and the foetus and its function is to fulfil the nutritional, respiratory, developmental and excretory needs of the foetus by connecting the foetus to mother's body.

What is population control ?

ANS : The prevention of unwanted births by applying proper techniques so that the population does not increase rapidly is called population control.

When does a girl attain puberty ?

ANS : A girl attains puberty at the age of about 10-12 years.

What do you mean by reproductive health ?

ANS : Reproductive health means capacity to reproduce without getting diseases like AIDS, gonorrhoea, syphillis, etc. which are contagious and transmitted sexually.

What is the full form of NACO ?

ANS : The full form of NACO is National AIDS Control Organisation.

ANS :

CONTROL AND COORDINATION IN LIVING ORGANISMS - II : BRIEF AND LONG ANSWERS

2007-06-25T11:05:00.000-07:00

ANSWER AS ASKED

*INDEX-TOPIC SEARCH

Explain : Tropism

ANS:

The movement of curvature of plants in the direction of stimuli is known as tropism.
Phototropism : When illuminated by a unidirectional light, the response of a growing plant by bending towards that light is called phototropism.

Geotropism : The downward movement of the roots of the plants, for fixation and absorption, as a response to the gravitational force is called geotropism.
Chemotropism : The movement of a plant or its part as a response to certain chemicals is called chemotropism. For example, germination of pollen grains and development of pollen tubes as a response to the chemicals secreted by the surface of the stigma.

Explain : Explain : Nastic movement

ANS:

The response by some plants to the external stimuli without any directional movement of growth or curvature towards that external stimuli is called nastic movement.
Examples :

The leaves of Mimosa (touch-me-not) are sensitive to touch. They droop when touched.
All insectivorous plants bend down or curl up when touched by insects.
A sunflower plant bends towards the sun.

Of the above examples, (i) and (ii) are examples of thigmonastic response and (iii) is an example of photonastic response.

Distinguish between tropic movement and nastic movement.

ANS :

Explain : Photoperiodism.

ANS:

Photoperiodism is the phenomenon in which the duration of light decides the flowering and germination in plants.
Plants are (i) Long-day plant and (ii) Short-day plant on the basis of the duration of light received by them.
Day natural plants do not respond to photoperiodism.
Plants respond to photoperiodic stimulus by a specialised pigment present in them called phytochrome.

Explain : Coordination in animals.

ANS:

All multicellular organisms, except porifera, have well-developed nervous system.
Hydra and other cnidarians possess nerve cells which form a nerve net in the body.

In invertebrates, the nerve net condenses into nerve mass called 'ganglion'.
Insects have a bilobed nerve mass (brain), nerve cord and nerve ganglia.

Higher organisms possess sensory organs (receptors) related to light, hearing, taste, touch and smell.
Receptors receive the stimulus and pass on the message to the brain through sensory neuron.
The brain transmits information to the effector organ (generally muscles and glands) through motor neuron.
The brain acts as the center for the analysis of information.
Motor neurons stimulate the muscles of the organ to respond.
Hormones also play an important role in control and coordination in animals.
In vertebrates there is a successive development of nervous system.
The nervous system of human beings is highly developed.
Hormones secreted by endocrine glands control various biochemical and mechanical activities carried out in the organisms. This is chemical control.

Write an explanatory note on HUMAN BRAIN.

ANS:

Human brain is the main coordinating center for all the activities of the human body.
It is protected by a bony box in the skull called cranium and three membranes called meninges.
There is a fluid called cerebrospinal fluid in the space between these membranes.
Cerebrospinal fluid acts as a cushion and protects the brain from mechanical shocks.
The brain is divided into three regions : (i) fore-brain (ii) mid-brain and (iii) hind-brain.
FORE-BRAIN consists of cerebrum and olfactory lobes.

Cerebrum is the most complex and specialised part of the brain.
It consists of two cerebral hemispheres.
It has sensory area to receive impulse from the sense organs and motor area to send impulse to muscles and effector organs.
Cerebrum has four regions having different centers of activity : (i) frontal lobe (ii) parietal lobe (iii) temporal lobe (iv) occipital lobe.

The frontal lobe possesses centres for voluntary muscular activities.
Parietal lobe possesses the centres for temperature control, smell and touch.
Temporal lobe possesses the centres for auditory and olfactory reception.
Occipital lobe possesses the centres for visual reception.

MID-BRAIN is a part of the brain stem and possesses the regions for visual reception, auditory reception and touch.
HIND-BRAIN consists of cerebellum, pons and medulla oblongata.

Cerebellum is situated on the posterior side of the fore-brain and it controls the rhythmic movement of muscles, body balance and posture.
Pons connects various parts of the central nervous system and cerebellum by the transverse bands of nerves.
Pons takes part in the regulation of respiration and helps in the movement of head as per audio-visual perception in coordination with medulla oblongata and spinal cord.
Medulla oblongata possesses the centres to regulate heartbeats, breathing, blood-pressure, sneezing, coughing, vomiting, swallowing, hiccups, etc.

Write in brief about Spinal cord.

ANS:

Spinal cord is a cylindrical structure.
It is the posterior extension of of medulla oblongata.
The vertebral column and meninges protect the spinal cord.
There are 31 pairs of spinal nerves arising from the spinal cord.
These nerves connect various organs of the body to the brain.
They help in the conduction of impulses from brain to organs and from organs to brain.
They also perform reflex action.

Explain : Reflex action

ANS:

An unconscious and involuntary response of effectors to the stimulus is called reflex action.
Due to reflex action we suddenly withdraw our leg when we step on a very hot or pricking object.
Similarly, our response towards very hot or very cold water is sudden and involuntary.
The reflex action is performed by the spinal cord when the brain is busy or at rest.
In reflex action, a message from the receptors is relayed by sensory nerves to the spinal cord and the spinal cord sends response via motor nerve to the effector organ.
This entire pathway is called 'REFLEX ARC'.

Write a note on Autonomous nervous system.

ANS:

The system which is responsible for the intervention in the activities of the organs located in the body cavity without the awareness of brain is called autonomous nervous system.
This system controls heart, blood vessels, glands, uterus and coelomic organs.
Autonomous nervous system is of two types : (i) sympathetic (ii) parasympathetic.
The involuntary actions of the body are controlled and regulated by the coordination of these two systems.
The effects of sympathetic and parasympathetic nervous systems are complimentory and contradictory.
For example : If the sympathetic system increases the heartbeats abnormally, the parasympathetic system decreases it and brings it back to normal.

Mention characteristics of hormones.

ANS:

They are specific chemical messengers.
Generally the origin and the target area of hormones are different.
They are directly poured into the blood (from the gland) and carried by blood circulation.
The effect of a hormone is either rapid or slow (i.e. it may increase or decrease the speed of some process). For example, acetylcholine increases the speed of the conduction of impulses whereas decreases (slows down) the effect of sex hormones.

Write a note on endocrine glands.

ANS:

Endocrine glands play an important role in coordination (in animals).
These are ductless glands and secrete hormones which are specific chemical messengers.
The main endocrine glands are hypothalamus, pituitary,, pineal, thyroid, parathyroid, pancreas, adrenal, testis and ovary.
Pituitary gland is called the master gland as it regulates the secretion of hormones by other endocrine glands.
The function of the pituitary gland is controlled by the secretion of hypothalamus.

Mention different endocrine glands, hormones secreted by them and the functions of these hormones.

ANS:

How is brain protected ?

ANS : The brain is surrounded by cranium, a bony box in the skull and three membranes called meninges. In the space between these membranes there is a fluid called cerebrospinal fluid. This fluid protects the brain against mechanical shocks. Thus brain is protected.

CONTROL AND COORDINATION IN LIVING ORGANISMS - I : MCQs AND SHORT ANSWERS

2007-06-16T11:11:00.000-07:00

*INDEX-TOPIC SEARCH

MULTIPLE-CHOICE QUESTIONS

SELECT THE CORRECT ALTERNATIVE:

______ is the complimentary system of nervous system.

Circulatory system
Endocrine system
Lymphatic system
Skeletal system

Plant hormones are called ______.

hypohormones
metahormones
phytohormones
cytohormones

The leaves of mimosa are sensitive to ______.

light
touch
heat
smell

A sunflower plant bends towards the sun. It is ______ response.

Thigmonastic
seismonastic
thermonastic
photonastic

All multicellular organisms, except ______, have well-developed nervous system.

porifera
mammals
arthropoda
insecta

Nerve mass in invertebrates is called ______.

brain
neuron
ganglion
pelvis

Hormones are secreted by ______.

endocrine glands
blood
midbrain
liver

The space between meninges is filled with ______.

lymph
blood plasma
cerebrospinal fluid
ACTH

______ is not the part of hindbrain.

cerebellum
pons
medulla oblongata
cerebrum

______ protects spinal cord.

Cranium
Vertebral column
Skull
Ribs

______ pairs of spinal nerves arise from spinal cord.

21
31
32
42

Which of the following organs is not controlled by autonomous nervous system ?

Heart
Uterus
Glands
Eyes

The effects of sympathetic and parasympathetic nervous systems are ______.

complimentary
contradictory
complimentary and contradictory
none of above.

Endocrine glands ______.

secrete plasma
secrete nutrients
secrete hormones
secrete antibodies

Acetylcholine ______.

increases the speed of conduction of impulses
decreases the speed of conduction of impulses
quickens the effect of growth hormones
controls pituitary gland

______ is called the master gland.

Pineal
Pituitary
Thyroid
Thymus

______ hormone regulates ionic balance.

Vasopressin
Thyroxin
Glucagon
Testosterone

______ is the hormone responsible for development of female characteristics.

Adrenalin
Testosterone
Thyroxin
Progesterone

______ is responsible for lowering glucose level in blood.

Glucagon
Oxytocin
Insulin
Adrenalin

______ is responsible for increasing glucose level in blood.

Glucagon
Oxytocin
Insulin
Adrenalin

Prolactin regulates ______.

blood pressure
heartbeat
mammary glands
glucose metabolism

Nerve net is found in ______.

sponges
hydra
earthworm
cockroach

Which multicellular organism lacks the nervous system ?

Hydra
Locust
Sponges
Tapeworm

Which hormone functions as a growth promotor ?

Auxin
Ethylene
Abscisic acid
Both B and C

Which of the following shows thigmonastic response ?

Sun flower
Insectivorous plants
Lotus
Bryophyllum

Which two organs are connected by pons with the help of transverse band of nerves ?

Nerves of brain and spinal cord
Both the cerebral hemispheres
Cerebellum and central nervous system
Sympathetic and parasympathetic

ANSWERS TO MCQs:

(1) B (2) C (3) B (4) D (5) A (6) C (7) A (8) C (9) D (10) B (11) B (12) D (13) C (14) C (15) A (16) B (17) A (18) D (19) C (20) A (21) C (22) B (23) C (24) A (25) B (26) C

SHORT QUESTIONS

ANSWER IN SHORT:

What is a stimulus ?

ANS : Any environmental factor that affects a living organism by showing changes is called a stimulus.

What is the structural and functional unit of the nervous system in multicellular organisms ?

ANS : Neuron is the structural and functional unit of the nervous system in multicellular organisms.

What does the nervous system do ?

ANS : The nervous system controls and coordinates various activities in the body of an organism.

Mention some factors (stimuli) to which plants respond.

ANS : Light, touch, water, gravitational force, insects, chemicals, etc are some stimuli to which plants respond.

Mention some plant hormones.

ANS : Auxin, gibberellin, cytokinin, abscisic acid, ethylene, etc are some plant hormones.

Mention growth hormones of plants.

ANS : Auxin, gibberellin and cytokinin are growth hormones of plants.

Which hormones in plants are responsible for ripening of fruits and shedding of leaves ?

ANS : Abscisic acid and ethylene are responsible for ripening of fruits and shedding of leaves.

Which plant hormones retard growth ?

ANS : Abscisic acid and ethylene retard growth.

What is tropism ?

ANS : The movement of curvature of plants in the direction of stimulus is known as tropism.

What is phototropism ?

ANS : The bending of a growing plant towards unidirectional light as a response to the illumination is called phototropism.

What is geotropism ?

ANS : Geotropism is a growth response of a plant to the force of gravitation (gravity) in which the roots show the downward movement.

What is hydrotropism ?

ANS : Hydrotropism is a growth response of a plant towards water shown by the growth of roots towards water.

What is chemotropism ?

ANS : Chemotropism is a growth response (movement) of a plant towards certain chemicals.

Give an example of chemotropism.

ANS : The germination of pollen grains and the development of pollen tube as a response to the chemicals secreted by the stigmatic surface is an example of chemotropism.

Define : Nastic movement.

ANS : A response of a plant to an external stimulus independent of its direction is called nastic movement.

What is thigmonastic response ?

ANS : The bending down or curling up of insectivorous plants, when touched by insects, is called thigmonastic movement.

What is photoperiodism ?

ANS : Photoperiodism is the response of some plants to the duration of light which mainly affects the flowering and germination in plants.

Which specialised pigment is responsible for the photoperiodic response by plants ?

ANS : Phytochrome is responsible for the photoperiodic response by plants.

Which organisms possess nerve net ?

ANS : Hydra and other cnidarians possess nerve net.

What does the nervous system of insects consist of ?

ANS : The nervous system of insects consists of a bilobed nerve mass (brain), nerve cord and nerve ganglia.

What is the function of receptors in nervous system ?

ANS : Receptors receive the stimuli and pass the message to the brain with the help of sensory neuron.

What is sensory neuron ?

ANS : Sensory neuron is a nerve cell which receives the stimuli from receptor and passes the message to the brain.

What is motor neuron ?

ANS : Motor neuron is a nerve cell which receives information from brain, transmits it to effector organ and stimulates it to respond.

Through what do hormones reach the target organ ?

ANS : Hormones reach the target organ through blood.

What protects brain in human beings ?

ANS : A bony box in the skull called cranium and three membranes called meninges protect the brain in human beings.

What is the function of cerebrospinal fluid ?

ANS : Cerebrospinal fluid acts as a cushion and protects the brain from mechanical shocks.

Mention three regions of brain.

ANS : The three regions of brain are : forebrain, midbrain and hindbrain.

What does forebrain consist of ?

ANS : Forebrain consists of cerebrum and olfactory lobes.

Mention the regions of cerebrum.

ANS : The regions of cerebrum are : frontal lobe, parietal lobe, temporal lobe and occipital lobe.

Mention the centres located in frontal lobe region.

ANS : Frontal lobe possesses the centres for voluntary muscular activities.

Mention the centres located in parietal lobe region.

ANS : Parietal lobe possesses the centres for temperature control, smell and touch.

Mention the centres located in temporal lobe region.

ANS : Temporal lobe possesses the centres for auditory and olfactory reception.

Mention the centres located in occipital lobe region.

ANS : Occipital lobe possesses the centre for visual reception.

Mention the regions of the midbrain.

ANS : The midbrain has the regions for visual reception, auditory reception and touch.

Mention the parts of brainstem.

ANS : Brainstem consists of midbrain, pons and medulla oblongata.

What does hindbrain consist of ?

ANS : Hindbrain consists of cerebellum, pons and medulla oblongata.

What is the function of cerebellum ?

ANS : Cerebellum controls the rythmic movement of muscles, body balance and posture.

Mention the centres possessed by medulla oblongata.

ANS : Medulla oblongata possesses the centres to regulate heartbeat, breathing, blood pressure, sneezing, vomiting, coughing, swallowing, hiccups, etc.

What is reflex action ?

ANS : Reflex action is an unconscious and involuntary response of effectors to a stimulus.

What is reflex arc ?

ANS : Reflex arc is the pathway through which a message from receptors is relayed by sensory nerves to the spinal cord which sends to effectors for response via motor nerve.

Which organ performs reflex action ? When ?

ANS : The spinal cord performs reflex action when the brain is busy or at rest.

What is meant by autonomous nervous system ?

ANS : The system responsible for the control of organs located in the body cavity without the awareness of the brain is called autonomous nervous system.

Mention the organs controlled by the autonomous nervous system.

ANS : Heart, blood vessels, glands, uterus, coelomic organs, etc are controlled by the autonomous nervous system.

Mention two types of autonomous nervous system.

ANS : Sympathetic nervous system and parasympathetic nervous system are the two types of autonomous nervous system.

Write the names of important glands.

ANS : Hypothalamus, pituitary, pineal, thyroid, parathyroid, thymus, pancreas, adrenal, testis, ovary, etc are important glands.

Which gland is called the master gland ?

ANS : Pituitary gland is called the master gland.

Why is pituitary gland called the master gland ?

ANS : Pituitary gland is called the master gland because it regulates the secretion of hormones by other glands.

What controls the functioning of pituitary gland ?

ANS : The secretion of hypothalamus controls the functioning of pituitary gland.

What is the function of trophic hormones ?

ANS : Trophic hormones regulate the secretion from other endocrine glands.

Which hormone controls male characteristics ?

ANS : Testosterone controls the male characteristics.

What is the function of parathyroid hormone ?

ANS : Parathyroid hormone regulates the level of calcium and phosphate in blood.

Name growth inhibitors in plants.

ANS : Abscisic acid and ethylene are growth inhibitors in plants.

Which structure protects brain ?

ANS : The structure consisting of cranium and three membranes called meninges having CSF (cerebrospinal fluid) in between them protects brain.

How are ganglia formed ?

ANS : Ganglia are formed by the condensation of nerve nets at some junction in the body of insects.

Explain the importance of cerebrospinal fluid.

ANS :Cerebrospinal fluid between the meninges of brain act as a cushion and protect the brain against mechanical shock.

What is the role of phytochrome in plants ?

ANS :Phytochrome is a specialized pigment present in plants which plays an important role in control and coordination of plants with environmental stimuli.

TRANSPORTATION, CIRCULATION & EXCRETION IN ORGANISMS - III : LONG ANSWERS

2007-05-22T10:16:00.000-07:00

GIVE ANSWER IN DETAIL

*INDEX-TOPIC SEARCH

Describe : Xylem.

ANS :

Xylem is a tissue associated with the transport of water in higher plants.
Water absorbed through roots is transported to the stem, branches, leaves and flowers by xylem.
Tracheids and vessels (tracheae) are the main components of xylem.
TRACHEIDS :

Tracheids are present in pteridophytes, gymnosperms and some angiosperms.
They are long, thin and spindle-shaped cells.
They are dead as their nuclei are disintegrated.
There is deposition of lignin on the inner wall of the cells which provides mechanical support to tracheids.
The cells are arranged one above the other.
At the junction of two cells, the wall possesses pits through which water is conducted upwards.

VESSELS (TRACHEAE) :

They are present in angiospermic plants.
They are short, comparatively broad and blunt at both ends.
They are dead because the cytoplasm and nucleus disintegrate during the formation of vessels.
The cells are arranged one above the other.
The transverse wall between the cells disintegrates to form a continuous passage for rapid upward transportation of water.
Lignin deposition on the inner wall provides mechanical support.

Describe : Transportation of Mineral Elements in Plants.

ANS :

Plants absorb minerals (inorganic dissolved salts) by roots from the soil.
Absorption of minerals occurs simultaneously with the absorption of water but the process is independent. The minerals are in direct contact with the water film in between the soil particles.
Water enters roots through root hair along with minerals.
It then moves through root cortex and endodermis to reach the root xylem.
Then the water which contains minerals reaches to the leaf through inter-connected stem xylem.
The transportation of water and minerals from the roots to the leaves is known as ascent of sap.
Only about 5% of the absorbed water is used up in photosynthesis and other metabolic processes while remaining 95% is lost as vapour by the process of transpiration.

Describe : Phloem.

ANS :

Phloem is a tissue which translocates the carbohydrates and essential substances produced in leaves, and hormones synthesized at the shoot and root tips from their place of origin to the site where needed.
In pteridophytic and gymnospermic plants, the main component of phloem is the sieve cell.
In angiospermic plants the main components of phloem are sieve tube and companion cell.
Sieve cells are living as they possess cytoplasm and nucleus.
Sieve tube cell and companion cell are formed by the longitudinal division of a single cell.
Sieve tube cells are broad and their nuclei are disintegrated.
Companion cells are narrow and possess nucleus.
Companion cells are arranged laterally and longitudinally to the sieve tube cells and their nuclei regulate metabolic activities carried out in sieve tube cells.
The transverse walls (sieve plates) present between sieve tube cells are perforated. These pores are known as sieve pores. Due to the sieve pores the food can be translocated in both upward and downward directions.
The transverse wall between two sieve cells does not have pores hence the translocation of food is indirect.
Transport of food from leaves to other parts of the plant is called translocation.
Translocation of food is necessary to fulfil daily requirements of energy, to replace worn out cells and for plant growth.

Write an explanatory note on blood.

ANS :

Blood is a living, red coloured, liquid connective tissue which circulates constantly throughout the body.
The two main components of blood are : (1) Blood Plasma (2) Blood Corpuscles.
BLOOD PLASMA :

It is pale yellow, nonliving, intercellular matrix with basic properties.
It consists of 90% of water and 10% of various constituents like plasma proteins, nutrients, metabolic waste, enzymes, hormones, vitamins, etc.

BLOOD CORPUSCLES :

Three main types of blood corpuscles in blood plasma are : (1) erythrocytes or red blood corpuscles (2) leucocytes or white blood corpuscles (3) thrombocytes (blood platelets).
They are formed from the undifferentiated stem cells found in the bone marrow of long bones.
ERYTHROCYTES (RBC) :

They are round, biconcave and light red in colour.
They do not possess nucleus and mitochondria.
The cell membrane is thin and elastic.
The cytoplasm contains haemoglobin which is a conjugated protein containing iron. Iron gives red colour to haemoglobin.
Haemoglobin absorbs oxygen from the walls of the lungs and forms oxyhaemoglobin. It takes this oxygen to every cell of the body.
Similarly haemoglobin collects carbon dioxide from each cell and brings it to lungs.
Since haemoglobin transports respiratory gases, it is known as respiratory pigment.
Every day about 30 lakh (3 million) erythrocytes die and as much of them are formed in the bone marrow.
The average life span of an erythrocyte is of 120 days.

LEUCOCYTES (WBC) :

The leucocytes vary in size, shape, appearance of the nuclei and the cytoplasmic constituents.
They do not contain any respiratory pigment.
They destroy pathogenic microorganisms and harmful toxic substances.
As they can pass through very thin membranes of capillaries, they are capable of reaching any part of the body.
Thus leucocytes provide protection to the body.
Lymphocytes (a type of WBC) produce immunoglobulins.

BLOOD PLATELETS :

They are very small, spindle-shaped fragments of cells in blood plasma.
They do not have any nucleus.
Their cell membrane is very thin and sensitive.
They rupture when they come in contact with air and release chemicals which initiate the process of blood clotting.

Describe : Clotting of Blood.

ANS :

Blood vessels rupture when there is a wound. Blood oozes out from the wound. This blood comes in contact with air and the process of clotting starts. The process of clotting takes place in the following manner.
The blood platelets rupture at the point of injury.
The ruptured platelets release thromboplastin.
Thromboplastin converts prothrombin found in the plasma into thrombin. This requires calcium.
Thrombin converts liquid fibrinogen (in the plasma) into solid fibrin fibres. These fibres form a network at the point of injury.
The blood corpuscles entangled in this network form a solid layer which dries up and forms a solid clot which stops the flow of blood.
After some time, a viscous pale yellow liquid (serum) oozes out from the periphery of the clot.

Explain : Blood Transfusion.

ANS :

The transfer of blood from a healthy donor to a person in need is called blood transfusion.
Carl Landsteiner discovered that there are special antigens on the surface of erythrocytes and different antibodies in plasma.
If the antigen on the erythrocytes of the donor's blood and the antibody in the recipient's plasma are same, it causes clotting of the patient's blood and may lead to death.
There are two types of antigens 'A' and 'B' on the erythrocytes.
The corresponding antibodies which clump the blood are 'a' and 'b', respectively.
We have four different blood groups : A, B, AB and O.
Blood transfusion is possible between two persons having same blood group.
A person with 'O' group can donate blood to any person but can receive the blood of 'O' group only.
A person with 'AB' group can receive blood from any person but can donate blood only to a person with 'AB' group.
Rhesus factor (Rh) is also matched for blood transfusion.

Describe : Structure and Working of Human Heart.

ANS :

STRUCTURE :

Human heart is located slightly on the left side in the space between two lungs.
It is conical and of the size of a closed fist.
It has four chambers. Two upper chambers are called atrium and the lower chambers are called ventricle.
Left atrium, right atrium, left ventricle and right ventricle are the four chambers based on their location in the heart.
The walls of the atria are thin whereas the walls of ventricles are thick.
All four chambers are separated from one another by partition called septa.
There is a bicuspid valve between left atrium and left ventricle whereas there is a tricuspid valve between right atrium and right ventricle.
These valves allow blood to flow from atrium to ventricle but do not allow it to flow from ventricle to atrium.
Heart is made of cardiac muscles.

WORKING :

When all four chambers of the heart are in relaxed state (diastolic stage), deoxygenated blood from the organs enters the right atrium through the superior and inferior vena cava.
At the same time oxygenated blood from lungs enters the left atrium through the pulmonary vein.
When both the atria are filled with blood , they contract and deoxygenated blood from right atrium is poured into right ventricle through tricuspid valve. Similarly the oxygenated blood from the left atrium is poured into left ventricle through bicuspid valve.
When both ventricles are filled with blood, they contract (systolic stage) and deoxygenated blood from the right ventricle goes to lungs through pulmonary artery and oxygenated blood from the left ventricle is distributed to all the parts of the body (except lungs) through aorta.
Since the blood flows twice through the heart it is called double circulation.

Write a note on blood vessels.

ANS : There are three types of blood vessels : (1) Arteries (2) Veins (3) Blood capillaries.

ARTERIES :

They carry blood from the heart to different organs of the body.
Their walls are thick and elastic.
They do not have valves.
After entering an organ, they branch into small arterioles.

VEINS :

They carry blood from different organs to heart.
Their walls are thin and nonelastic.
They have valves.
After exiting an organ they unite to form vena cava.

BLOOD CAPILLARIES :

Around the tissues, the arterioles break up into fine vessels called capillaries.
They are thin and narrow.
Capillaries unite to form small blood vessels called venules.
Venules unite to form veins.
Necessary substances diffuse from blood into the tissues through thin walls of the capillaries.

Write a note on Lymphatic system.

ANS :

The transparent fluid that oozes out in the surrounding intercellular space and the tissue cells from the blood flowing in the capillaries is called lymph.
It is a pale yellow liquid connective tissue containing lymphocytes.
It is in direct contact with the tissue cells and provides them the necessary substances.
The excretory substances formed in the tissue cells diffuse into the lymph.
After this exchange of essential substances and excretory substances the lymph reaches the lymph vessel.
The lymphatic system begins with lymph vessels.
The lymphatic system consists of lymphatic vessels, lymphatic capillaries, lymph nodes and lymph glands.
Lymph circulates from tissue cells to the heart.

Explain : Excretion and Osmoregulation.

ANS :
EXCRETION :

During biochemical processes performed by body cells many unnecessary and toxic by-products are formed along with useful substances.
These unnecessary toxic substances are called excretory substances.
Excretion is the biological process involved in the removal of liquid excretory substances from the body.

OSMOREGULATION :

The amount of water in the body may increase or decrease due to biological processes.
Osmoregulation is the process of maintaining the required amount of water and proper ionic balance in the body.
Excretion and osmoregulation occur simultaneously.
Methods of excretion, the type of excretory products and the amount of water required for excretion are correlated to the habitat of the organism, availability of water and necessity of osmoregulation.
Different animals have various structures for excretion and osmoregulation.
Amoeba has a contractile vacuole, sponges have osculum, hydra has oral opening, platyhelminthes have flame cells, earthworms have nephridia and human beings have kidneys.
Fresh water organisms get large amount of water easily. In order to remove this excess water they excrete ammonia which is soluble in water.
Marine and terrestrial animals possess mechanism to conserve water as they do not get fresh water easily. Their excretory system is capable of reabsorbing water and they excrete concentrated urine after a long interval. Urine mainly contains urea.
Desert animals convert the concentrated waste into crystals of uric acid as they cannot afford to lose water.
Birds do not have urinary bladder. They excrete waste in the form of uric acid.

Describe excretion in earthworm.

ANS :

The body of earthworm is divided into a series of segments separated internally by septa.
Excretory organs of the earthworm are called nephridia which are absent in first three segments.
Nephridia are coiled tubes.
There are three types of nephridia : (i) septal (ii) pharyngeal (iii) integumentary.
There are two types of excretion : (i) enteronephric (ii) exonephric.
In enteronephric excretion the excretory products are poured into alimentary canal through nephridia.
In exonephric excretion the excretory products are thrown out of the body through skin.
There is a funnel-like structure called nephrostome at the anterior end of the nephridium.
Its posterior end has an opening called nephridiopore.
The fluid carrying wastes enters nephrostome.
The cilia present in the tubule help the fluid to move through the nephridium.
During the process useful substances are reabsorbed by the cells lining the tubules.
These useful substances are then passed into the blood.
The remaining waste fluid is thrown out through nephridiopore.

Describe excretion in human being.

ANS :
EXCRETORY SYSTEM :

Excretory organs consist of a pair of reddish brown bean-shaped kidneys, located in the abdomen.
From each kidney opens an excretory tube called ureter into the urinary bladder.
The bladder passes into a muscular tube called urethra.
Urethra opens out as small opening called urinary opening.
Kidney is divided into cortex and medulla.
Kidney consists of excretory units called nephrons.

STRUCTURE OF A NEPHRON :

A kidney has very minute tubular and convoluted structures known as uriniferous tubules (nephrons).
A kidney has about 10 lac (one million) such units.
Each nephron has a double-walled cup-shaped structure called Bowman's Capsule at its beginning.
Bowman's capsule encloses a small group of capillaries called glomerulus.
The short region after Bowman's capsule is called the neck.
The tubule after the neck is narrow and coiled.
It consists of proximal convolution, Henle's loop and distal convolution.
The distal convolutions of many nephrons join a common collecting duct which leads to the renal pelvis.
Renal pelvis opens into the ureter.

PROCESS OF FORMATION OF URINE :

Renal arteries bring blood containing the waste material to the kidney.
By ultrafiltration the blood is filtered out from blood capillaries into Bowman's capsule under pressure.
During the passage of this filtrate through tubular parts of nephron, useful products such as water, amino acids, minerals, ions, etc. are reabsorbed by blood capillaries surrounding the nephron.
The remaining fluid contains excretory substance called urine which passes into urinary bladder through ureter. When the bladder is filled with urine, it contracts and urine passes out of the body.

Mention functions of blood.

ANS :

Blood carries oxygen from lungs to other parts of the body.
It brings carbon dioxide from all parts of the body to lungs.
It carries digested food (nutrients) from alimentary canal to all parts (cells) of the body.
It carries hormones from different glands to the target area in the body.
It carries excretory waste products to throw them out through urine.
It regulates body temperature.
It fights pathogenic organisms through WBC and protects the body from various diseases.

TRANSPORTATION, CIRCULATION & EXCRETION IN ORGANISMS - II : BRIEF ANSWERS

2007-05-17T20:39:00.000-07:00

ANSWER IN BRIEF

*INDEX-TOPIC SEARCH

Describe : Ascent of sap.
ANS:

Plants absorb water and minerals from the soil through root hairs.
Water along with minerals then moves through root cortex and endodermis to reach the root xylem.
From root xylem they enter the interconnected stem xylem which branches into leaves.
This transportation of water and minerals from the roots to the leaves is known as the ascent of sap.

Explain : Rhesus factor.
ANS:

Blood contains an antigen called Rh factor (Rhesus factor).
A person with Rh antigen in blood is called Rh +ve and one lacking it is called Rh -ve.
Incompatibility of Rh factor causes problems.
If an Rh +ve man marries an Rh -ve woman, the birth of the first child is normal. But mother's blood forms antibodies against Rh antigen.
If the second child is Rh +ve, the antibody in mother's blood reacts with the Rh antigen of the foetus and causes problems, sometimes leading to the death of the child.

Describe excretion and osmoregulation in amoeba.
ANS:

Amoeba is a fresh water unicellular organism.
It has a contractile vacuole for excretion and osmoregulation.
The waste produced in the cell enters contractile vacuole along with water.
The size of the contractile vacuole gradually increases and then it moves closer to the plasma membrane.
It bursts after touching the plasma membrane and releases the excretory substances into the surrounding water by diffusion.

Give reason : An Rh(-ve) woman should not marry an Rh(+ve) man.
ANS: [Refer to last two points mentioned in the answer about Rhesus factor].

Distinguish between xylem and phloem.

ANS:

Distinguish between blood and lymph.

ANS :

Distinguish between artery and vein.

ANS :

TRANSPORTATION, CIRCULATION & EXCRETION IN ORGANISMS - I : MCQs & SHORT ANSWERS

2007-05-07T20:06:00.000-07:00

*INDEX-TOPIC SEARCH

MULTIPLE-CHOICE QUESTIONS

SELECT THE CORRECT ALTERNATIVE:

______ is associated with the transport of water in plants.

Xylem
Phloem
Chloroplast
Aerenchyma

Tracheae are found in ______ plants.

pteridophytes
gymnosperms
angiosperms
all three

The inner wall of the tracheids and tracheae shows deposition of ______.

starch
glucose
lignin
protein

Which of the following is not a property of blood plasma ?

It is pale yellow
It is nonliving
It is acidic
It contains hormones

Which of the following is not a blood corpuscle ?

Leucocyte
Erythrocyte
Thrombocyte
Nymphocyte

Which of the following is true for human erythrocytes ?

They are biconvex.
They have nucleus.
They contain haemoglobin.
They do not have nucleus but possess mitochondria.

______ is a respiratory pigment.

Haemoglobin
Chlorophyll
Mesophyll
Adrinalin

The lifespan of erythrocytes is about ______ days.

100
120
140
180

Which of the following is false ?

Erythrocytes are light red in colour.
Haemoglobin is a respiratory pigment.
Lymphocytes produce immunoglobulins.
Thrombocytes destroy pathogens.

______ is a necessary mineral for clotting of blood.

Calcium
Potassium
Iron
Zinc

______ converts liquid fibrinogen into solid fibres of fibrin.

Thromboplastin
Oxyhaemoglobin
Immunoproteins
Thrombin

There are ______ types of antigens on the erythrocytes.

two
three
four
five

The blood group of a person is O and Rh (-ve). He can donate blood to...

any person
a person with group O
A person with Rh (-ve)
none

Which of the following is true ?

Heart purifies blood.
Heart separates excretory products from blood.
Heart circulates blood.
Blood flows from heart to lungs.

The relaxed state of yeart is called ______.

Diastolic state
Systolic state
Thermostatic state
Primary state.

The structure for excretion and osmoregulation in sponges is ______.

osculum
contractile vacuole
nephridia
flame cell

Urine mainly consists of ______.

Uranium
Urea
CO₂
sugar

Birds excrete wastes in the form of ______.

urea
proteins
uric acid
water

Which structure is responsible for transportation of water in pteridophytes ?

Tracheids
Tracheae
Sieve cells
Sieve tubes

Which structure has lignified cell wall ?

Sieve tube
Tracheids
Trachea
Sieve cells

Which blood cells contain haemoglobin ?

RBC
WBC
Platelets
Lymphocytes

Which blood cells produce immunoglobin ?

Platelets
Erythrocytes
Lymphocytes
Leucocytes

Which chemical is released when blood cells rupture ?

Prothrombin
Fibrin
Thrombin
Thromboplastin

Where are antigens for blood group located ?

WBC
RBC
Platelets
Blood plasma

How many chambers are present in human heart ?

1
2
3
4

Where is bicuspid valve found in human heart ?

Between two atria
Between left auricle and left ventricle
Between two ventricles
Between right auricle and right ventricle.

Through which parts of the heart does oxygenated blood flow ?

Both atria
Left auricle and left ventricle
Both ventricles
Right auricle and right ventricle

Where does deoxygenated blood get oxygenated ?

Atrium
Heart
Lungs
Kidneys

Which type of blood flows through all arteries ?

Impure
Pure
Toxic
With nitrogenous waste

What is the shape of human heart ?

Round
Bean shaped
Conical
Triangular

Carboxy-haemoglobin is formed when haemoglobin reacts with...

CO
CO₂
O₂
CH₄

SHORT QUESTIONS

ANSWER IN SHORT:

Define : Transportation.

ANS : The movement of different types of substances absorbed or synthesized in one part of the body to another part of the body is called transportation.

Mention two main components of xylem responsible for the transportation of water.

ANS : Tracheids and tracheae (vessels) are two main components of xylem responsible for the transportation of water.

What are tracheids ?

ANS : Tracheids are long, thin and spindle shaped cells of xylem of a plant.

Why are tracheids dead cells ?

ANS : Tracheids are dead cells because their nuclei are disintegrated.

What is ascent of sap ?

ANS : The transportation of water and minerals from the roots to the leaves is known as the ascent of sap.

How much of the water absorbed by the plants is used up in photosynthesis and other metabolic processes ?

ANS : Only about 5% of water absorbed by the plants is used up in photosynthesis and other metabolic processes.

Define : Transpiration.

ANS : The process by which water absorbed by plants through roots is lost (thrown out) in the form of vapours is called transpiration.

Where are plant hormones synthesized ?

ANS : Plant hormones are synthesized at the shoot and root tips.

What is the function of phloem ?

ANS : Phloem translocates carbohydrates, essential substances, plant hormones, etc. from their place of origin to the site where needed.

In which plant is a sieve cell the main component of phloem ?

ANS : In pteridophytes and gymnosperms sieve cell is the main component of phloem.

In which plants are the sieve tube and companion cell the main components of phloem ?

ANS : In angiospermic plants the sieve tube and companion cell are the main components of phloem.

What regulates metabolic activities carried out in the sieve tube cells ?

ANS : The nucleus of the companion cell regulates metabolic activities carried out in the sieve tube cells.

Define : Sieve pores.

ANS : The perforations in the transverse walls (sieve plates) present between sieve tube cells are called sieve pores.

Define : Translocation.

ANS : The transport of food from leaves to other parts of plants is called translocation.

What is the need for translocation of food ?

ANS : Translocation of food is necessary to fulfil the daily requirement of energy, to replace the worn out cells and for the growth of the plant.

Define : Circulatory system.

ANS : The system associated with the transport of various substances like nutrients, hormones, enzymes, respiratory gases, excretory products, etc. is called circulatory system.

Mention two main components of blood.

ANS : Blood plasma and blood corpuscles are the two main components of blood.

Mention three main types of blood corpuscles.

ANS : Erythrocytes (RBC), leucocytes (WBC) and thrombocytes (platelets) are three types of blood corpuscles.

Why is haemoglobin called respiratory pigment ?

ANS : Haemoglobin is called respiratory pigment because it transports respiratory gases (O₂ and CO₂) between lungs and organs.

Where are erythrocytes formed ?

ANS : Erythrocytes are formed in the bone marrow.

Which type of WBC produce immunoglobulins ?

ANS : Lymphocytes produce immunoglobulins.

What is serum ?

ANS : Serum is a viscous pale yellow liquid that oozes out from the periphery of a blood clot.

Define : Blood transfusion.

ANS : The transfer of blood from a healthy donor to a needy patient is called blood transfusion.

Who discovered the presence of special antigens on the surface of erythrocytes ?

ANS : Carl Landsteiner discovered the presence of special antigens on the surface of erythrocytes.

Mention different blood groups in human beings.

ANS : The blood groups present in human being are : A, B, AB and O.

What happens during the diastolic state of heart ?

ANS : During diastolic state of heart, deoxygenated blood from organs enters right atrium through the superior and inferior vena cava and oxygenated blood from lungs enters left atrium through pulmonary vein.

Why is circulation of blood through heart called 'double circulation' ?

ANS : The circulation of blood through heart is called 'double circulation' because deoxygenated blood from body organs passes twice through heart before it reaches the organs in oxygenated form.

Define : Artery.

ANS : The blood vessel which carries blood from heart to different organs of the body is called artery.

Define : Vein.

ANS : The blood vessel which carries blood from different organs to the heart is called vein.

What is lymph ?

ANS : The transparent fluid which oozes out in the surrounding intercellular space and the tissue cells from the blood flowing in the capillaries is called lymph.

Which cells does lymph contain ?

ANS : Lymph contains lymphocytes.

What constitutes lymphatic system ?

ANS : Lymphatic system consists of lymphatic vessels, lymphatic capillaries, lymph nodes and lymph glands.

Define : Excretion.

ANS : The biological process involved in the removal of liquid excretory substances from the body is called excretion.

Define : Osmoregulation.

ANS : The process of maintaining the required amount of water and proper ionic balance in the body is called osmoregulation.

What is the structure for excretion and osmoregulation in amoeba known as ?

ANS : The structure for excretion and osmoregulation in amoeba is known as contractile vacuole.

What is the structure for excretion in earthworm known as ?

ANS : The structure for excretion in earthworm is known as nephridia.

What is the structure for excretion in platyhelminthes known as ?

ANS : The structure for excretion in platyhelminthes is known as flame cells.

What does hydra have for excretion and osmoregulation ?

ANS : Hydra has oral opening for excretion and osmoregulation.

Mention the types of nephridia in earthworm.

ANS : The types of nephridia in earthworm are : (i) septal (ii) pharyngeal and (iii) integumentary.

Which two types of excretion is shown by the earthworm ?

ANS : Enteronephric excretion and exonephric excretion are the two types of excretion shown by the earthworm.

What is enteronephric excretion ?

ANS : In enteronephric excretion the excretory products are poured into the alimentary canal through nephridia.

What is exonephric excretion ?

ANS : In exonephric excretion the excretory products are thrown out of the body through the skin.

Where are human kidneys located ?

ANS : Human kidneys are located in the abdomen on the dorsal side.

What is ultrafiltration ?

ANS : The filtration of blood carrying waste material under pressure in glomerulus is known as ultrafiltration.

What do desert animals do for osmoregulation ?

ANS : Since desert animals cannot afford to lose water, they convert the concentrated waste into crystals of uric acid.

Which substance provides mechanical support to the walls of xylem ?

ANS : Lignin provides mechanical support to the walls of xylem.

What is transported through sieve plate ?

ANS : Food is transported through sieve plate.

Mention the colour of blood and lymph.

ANS : The colour of blood and lymph is red and pale yellow respectively.

What is the shape of human erythrocytes ?

ANS : Human erythrocytes are round, biconcave in shape.

Which mineral is present on haemoglobin ?

ANS : Iron is present in haemoglobin.

Where are blood cells produced in our body ?

ANS : Blood cells are produced in the bone marrow of long bones.

Mention two functions of WBC.

ANS : The two functions of WBC are : (i) They destroy pathogenic microorganisms. (ii) They destroy harmful substances.

Give examples of enucleated blood cells.

ANS : RBC (erythrocytes) and platelets are enucleated blood cells.

State the function and location of stem cells.

ANS : Stem cells are located in the bone marrow of long bones and they produce all types of blood corpuscles.

Where is thromboplastin produced ?

ANS : Thromboplastin is produced at the point of injury where blood vessels rupture.

Which mineral is needed to convert prothrombin into thrombin ?

ANS : Mineral calcium is needed to convert prothrombin into thrombin.

What converts fibrinogen to fibrin ?

ANS : Thrombin converts fibrinogen to fibrin.

Where are blood antigens located ?

ANS : Blood antigens are located on the surface of erythrocytes.

Why does right atrium appear dark in colour ?

ANS : Right atrium appears dark in colour because it has deoxygenated blood in it which is dark in colour.

Why does left venticle appear red in colour ?

ANS : Left ventricle appears red in colour because it has oxygenated blood in it which is red in colour.

What type of valves are found in veins ?

ANS : The valves in veins are of the type which allows blood to flow towards heart and stops it from flowing in opposite direction.

Where is tricuspid valve present in human heart ?

ANS : Tricuspid valve is present between right atrium and right ventricle of heart.

To which part of the body does pulmonary artery supply blood ?

ANS : Pulmonary artery supplies blood to lungs (from heart).

What is the function of pulmonary vein ?

ANS : Pulmonary vein collects blood from lungs and supplies it to the left atrium.

Define : Conduction.

ANS : The upward movement of water (absorbed by roots) through tracheids is called conduction.

Define : Double circulation.

ANS : The circulation of blood through heart is called double circulation because deoxygenated blood from body organs passes twice through heart before it reaches the organs in oxygenated form.

What are blood capillaries ?

ANS : Fine, thin-walled and narrow tubular branches of arterioles which reunite to form venules are called blood capillaries.

Define : Companion cell.

ANS : The cells arranged laterally and longitudinally to sieve tube cells in the phloem of angiospermic plants are called companion cells.

Which organelle is absent in human RBC ?

ANS : Nucleus and mitochondria are absent in RBC.

State the location and function of stem cells.

ANS :Stem cells are located in bone marrow of long bones and their function is of formation of all types of blood cells.

NUTRITION AND RESPIRATION IN ORGANISMS - III : LONG ANSWERS

2007-04-18T04:31:00.000-07:00

GIVE ANSWER IN DETAIL

*INDEX-TOPIC SEARCH

Define nutrition, mention its types and describe each type with examples.

ANS :

NUTRITION : The process of intake of nutrients and their utilisation in every living cell of the body is called nutrition.
TYPES OF NUTRITION : Based on the mode of obtaining food by the organisms, nutrition is classified into two main types-(i) Autotrophic nutrition (ii) Heterotrophic nutrition.
AUTOTROPHIC NUTRITION : Green plants and some bacteria prepare their own food from inorganic materials like carbon dioxide, water and minerals using pigment chlorophyll. These are called autotrophic organisms and their mode of nutrition is called autotrophic nutrition.
HETEROTROPHIC NUTRITION : Heterotrophic organisms are those which cannot synthesize their own food. These organisms obtain their food from plants and other animal sources. This type of nutrition is called heterotrophic nutrition. In this type of nutrition, the organic components of the food are digested into simple forms and then utilised by the organism. All animals, bacteria and examples of heterotrophic organisms.

Heterotrophic nutrition is classified into three types : (i) Saprophytic nutrition (ii) Parasitic nutrition (iii) Holozoic nutrition.
SAPROPHYTIC NUTRITION : Organisms obtaining nutrients from dead and decaying organic matter are called saprophytes and their mode of nutrition is called saprophytic nutrition. Many species of bacteria and different types of fungi are saprophytes.
PARASITIC NUTRITION : If an organism depends on another living organism for nutrition, its mode of nutrition is called parasitic nutrition. Such organisms are called parasites and the organism from which they obtain nutrition is called host. The host organism is harmed by the parasite. Parasitic nutrition is observed in some bacteria, fungi, flowering plants like cuscuta and animal like ascaris.
HOLOZOIC NUTRITION : Holozoic nutrition involves intake of parts of plants or animals or an organism as a whole by the process of ingestion which is then digested and absorbed. Some examples are amoeba, frog, insects, human being, etc.

Describe Photosynthesis in detail.

ANS : Plants synthesize their own food by the process of photosynthesis. Photosynthesis is the process in which plants synthesize food from carbon dioxide and water with the help of sunlight and chlorophyll.

Photosynthesis takes place in two phases : (1) Light Phase (2) Biosynthetic Phase.

LIGHT PHASE : This phase is called light phase because the presence of light is necessary for it to occur.

The chlorophyll molecule absorbs light energy in the form of photons, gets excited and emits electrons. These electrons travel through electron transport chain present in the chloroplast. During this ATP is synthesized from ADP and inorganic phosphate by photophosphorylation. This ATP is used as energy source in biosynthetic phase.

During the light phase photolysis of water takes place.

The H⁺ ions reduce NADP (Nicotinamide Adenine Dinucleotide Phosphate) into NADPH₂.

The oxygen released during photosynthesis comes from water and not from carbon dioxide.

The whole process takes place in the grana of chloroplast.

BIOSYNTHETIC PHASE : In this phase the ATP and NADPH₂ formed during the light phase are used for the synthesis of carbohydrates from carbon dioxide. This process takes place in the stroma of the chloroplast.

Calvin Cycle : It is called Calvin cycle as Calvin and Benson had discovered it.

In this process, the carbon dioxide reacts with Ribulose biphosphate (RuBP) and enters the biosynthetic phase. In the end of the cycle carbohydrate is synthesised and RuBP is regenerated.

The process of photosynthesis is affected by light, temperature, water and carbon dioxide.

Explain the factors that affect Photosynthesis.

ANS : The factors that affect photosynthesis are : (1) light (2) temperature (3) water (4) carbon dioxide.

LIGHT : Intensity and quality of light affect photosynthesis. Chlorophyll absorbs mostly red and orange regions of visible spectrum. The rate of photosynthesis is more in red and orange light. Rate of photosynthesis increases at low intensity of light and decreases at high intensity.

TEMPERATURE : Photosynthesis takes place in the presence of enzymes. At low temperatures the activity of enzymes is low and the rate of photosynthesis is low. As the temperature increases, the enzymes get activated and the process of photosynthesis accelerates. But at very high temperatures the enzymes become denatured and the rate of photosynthesis decreases.

WATER : The rate of photosynthesis decreases under water-deficient conditions as the stomata remain closed to reduce transpiration. This stops gaseous exchange and hence the photosynthesis as carbon dioxide is not available.

CARBON DIOXIDE : The rate of photosynthesis increases with the increase in the concentration of carbon dioxide up to a certain level. Beyond that level it may have inhibitory effect on the rate of photosynthesis.

Explain : Nutrition in Amoeba.

ANS : The mode of nutrition in amoeba is holozoic. The process of obtaining food is called phagocytosis. Amoeba feeds on microscopic organisms floating on water. The nutrition involves processes like ingestion, digestion, assimilation and egestion.

Process : Amoeba forms pseudopodia to take food. When the tips of

pseudopodia touch each other, the membrane at that point dissolves and the food is encaptured along with lysosomes into food vacuole. Digestive enzymes present in the lysosome digest the food. The digested food diffuses into the cytoplasm and utilized by the cell. This is called assimilation. The undigested food left in the food vacuole is thrown out of the body. This is called egestion.

Describe Nutrition in grasshopper (locust).

ANS : Grasshopper is a herbivorous insect feeding on leaves of plants. The alimentary canal of the grasshopper is divided into three parts : (1) foregut (2) midgut (3) hindgut.

Foregut : It starts from mouth and extends up to gizzard. It consists of a short pharynx, narrow oesophagus and crop. The gizzard has a muscular wall and its lumen is lined with cuticle which forms six chitinous teeth. A pair of salivary glands along the crop opens into the cavity of the mouth through ducts.

Midgut : It is the region between gizzard and hindgut. At its anterior end there are fingerlike projections called hepatic caecae which open into the midgut and secrete digestive enzymes.

Hindgut : It is the region between the midgut and anus. It consists of three parts. An anterior ileum, a middle colon and a posterior rectum. The rectum opens outside through the anus. The junction of midgut and hindgut has many yellow threadlike minute tubules called Malphighian tubules which work as excretory organs.

PROCESS OF DIGESTION :Grasshopper holds the food with fore legs and ingests it inside the mouth where the food mixes with saliva. The saliva lubricates and makes the food soft. Its digestive enzyme digests starch. The food then passes to the crop via oesophagus where it is stored temporarily. Then it passes into the gizzard where it is ground by chitinous teeth and then passes into the midgut. Here the food is digested by enzymes secreted by hepatic caecae. The digested food is absorbed and the indigested food passes into the hindgut from where it is egested out through the anus.

Write an explanatory note on Human Digestive System.

ANS : Human digestive system consists of alimentary canal and accessory digestive glands. Alimentary canal consists of mouth, buccal cavity, pharynx, oesophagus, stomach, small intestine, colon, rectum and anus. Accessory digestive glands are salivary glands, liver and pancreas. They secrete digestive juices.

The alimentary canal begins with mouth which is located at the anterior end between two lips. The mouth opens into the buccal cavity which lies between the upper and lower jaws.

The muscular tongue at the floor of the buccal cavity helps in digestion of food.

The upper and lower jaws have four kinds of teeth. (1) Incisors for cutting (2) Cannines for tearing (3) Premolars and (4) Molars for chewing and grinding.

The posterior region of buccal cavity is called pharynx which opens into the oesophagus. The oesophagus opens into the stomach which is situated on the left side of the abdomen. The inner wall of the stomach secretes gastric juices. The stomach opens into the duodenum through pyloric valve which is guided by sphincter muscle.

The proximal region of small intestine is called duodenum. It is U-shaped and receives the secretion of liver and pancreas through a common bile duct. The middle region of small intestine is called jejunum and the distal region is called ileum.

Ileum is about 7 m long. The inner wall of the small intestine has long fingerlike projections called villi. These increase the surface area for absorption. The small intestine opens into the large intestine. There is a projection called vermiform appendix at the junction of two intestines.

The large intestine opens into the rectum which, in turn, opens out by anus. The anus is guarded by sphincter muscles.

Explain the exchange of gases in plants.

ANS :
EXCHANGE OF GASES IN ROOT AND STEM :

Oxygen is present between soil particles.
Roots take up oxygen by the process of diffusion through the root hairs of piliferous layer.
This oxygen then passes into other root cells.
Carbon dioxide from the root cells moves out into the soil through the similar route.
Root hairs are not present in all parts of the root.
The parts devoid of root hair have a layer of dead cells having tiny openings called lenticels. In woody plants the bark has lenticels.
Gaseous exchange occurs between the soil and inner living cells through lenticels.

EXCHANGE OF GASES IN LEAVES :

There are numerous tiny apertures called stomata on the leaf surface.
During respiration the atmospheric oxygen diffuses into the stomata and then into the leaf cells.
Stomata opens and releases carbon dioxide into atmosphere when the concentration of carbon dioxide increases in the cells.

Write Important Points on Respiration in Animals.

ANS :

Different animals have different respiratory organs.
Amoeba and paramoecium exchange gases through body wall.
Fish respire through gills.
Frog, lizard, birds and man have lungs for respiration.
Frogs respire through skin and lungs.
Atmospheric oxygen diffuses through their moist skin into the blood capillaries.
Carbon dioxide from the blood diffuses out into the atmosphere through skin.
Similar process occurs during the exchange of gases in lungs.
The exchange process occurs according to the Law of Partial Pressures of gases.
Insects like locust, housefly, cockroach, etc. possess trachea for respiration.
The tracheal system reaches every part of the body.
Air enters the tracheal system through spiracles situated on the lateral sides of the body.
Oxygen reaches each and every cell through trachea.
Carbon dioxide released by the cells moves out to the atmosphere through spiracles.

[Last 5 points describe respiration in insects.]

Describe Respiration In Human Being.

ANS :
HUMAN RESPIRATORY SYSTEM :

The human respiratory system is well-developed.
It consists of nostrils, nasal cavity, pharynx, larynx, trachea, bronchi and lungs.
Nostrils are the opening of nasal cavity.
The oxygen-rich air enters nasal cavity through the nostrils.
The deoxygenated air (containing CO₂) is expelled out through nostrils.
The mucus in nasal cavity keeps it moist so that dust particles and microbes in the air are trapped there and do not enter lungs.
Nasal cavity also warms and moistens the air.
Air enters pharynx through nasal cavity and then into trachea (wind pipe) through a slit called glottis.
Glottis is protected by a cartilaginous flap called epiglottis.
As glottis is covered by epiglottis during the swallowing of food, the food does not enter the wind pipe.
Trachea is a wide tubular structure supported by C-shaped cartilaginous rigs.
Trachea divides into two bronchi which lead into the lungs.
There is a pair of lungs situated in thoracic cavity.
The lungs are covered by two membranes called pleura.
Brochi branch into many bronchioles in the lungs. Each bronchiole terminates in a sac called alveolar sac.
The walls of the alveoli are thin and covered by blood capillaries.

MECHANISM OF BREATHING :

Intake of air into lungs is called inhalation.
When the diaphragm and the muscles attached to the ribs contract, the volume in the thoracic cavity increases, the air pressure decreases and the oxygen-rich air from the atmosphere enters the lungs through nostrils.
Alveolar sacs are filled with oxygen-rich air and exchange of gases occurs.
When the diaphragm relaxes the volume of the thoracic cavity decreases, the pressure increases and the air containing carbon dioxide is expelled out of lungs through nostrils.
This is called exhalation.
The process of inhalation and exhalation is collectively called breathing.

EXCHANGE OF GASES IN TISSUES :

Respiratory gases are exchanged between the blood and the tissues.
Oxygen is utilised in the tissues and carbon dioxide is released.
The blood coming from lungs to the tissues has higher concentration of oxygen and lower concentration of carbon dioxide.
The difference in concentration induces exchange of gases between tissue and blood capillaries.

The end result of respiration process is that the oxidation of simple food molecules like glucose in mitochondria releases energy which is stored in ATP.

Distinguish between autotrophic nutrition and heterotrophic nutrition.

ANS :

Distinguish between photosynthesis and respiration.

ANS:

NUTRITION AND RESPIRATION IN ORGANISMS - II : BRIEF ANSWERS

2007-04-17T11:17:00.000-07:00

ANSWER IN BRIEF

*INDEX-TOPIC SEARCH

Describe Aerobic respiration.

ANS: The respiration that takes place in the presence of oxygen is called aerobic respiration. Majority of the organisms show aerobic respiration.

During aerobic respiration glucose is completely broken down into carbon dioxide and water and the energy that is released is stored in ATP.

Since the process takes place in the cell it is called Cellular respiration or Internal respiration.

Describe Anaerobic respiration.

ANS: Anaerobic respiration takes place in the absence of oxygen. It is seen in micro-organisms like bacteria, yeast, fungi, endoparasites and in muscle cells.

In plants, carbon dioxide and ethanol are formed as end products.

Lactic acid is formed as end product in muscle cells.
How does the respiration in plants differ from that in animals ?

ANS: The respiration in plants differs from that in animals in the following ways :

All parts of a plant like root, stem and leaf perform respiration individually.
There is little transport of gases from one part of plant to another.
The rate of respiration in plants is much slower than that in animals.

Distinguish between aerobic and anaerobic respiration.

ANS:

What is photolysis? Give reaction.

ANS:Photolysis is the process of breaking a molecule with the help of light. For example, photolysis of water during light phase of photosynthesis:

H₂O ---> 2H⁺ + 1/2 O₂ + 2e^-

Distinguish between breathing and (cellular) respiration.

ANS:

NUTRITION AND RESPIRATION IN ORGANISMS - I : MCQs & SHORT ANSWERS

2007-04-13T06:23:00.000-07:00

*INDEX-TOPIC SEARCH

MULTIPLE-CHOICE QUESTIONS

SELECT THE CORRECT ALTERNATIVE:

The autotrophic organisms contain ______ pigment.

methylene blue
chlorophyll
phenolphthalin
carbon black

Oxygen released during photosynthesis comes from ______.

water
carbon dioxide
chloroplast
sunlight

Rate of photosynthesis is more in ______ and ______ light.

red, green
red, orange
yellow, orange
green, orange

The process of obtaining food in amoeba is called ______.

pyrolysis
phosphorylation
phagocytosis
phenocytosis

The cavity between the upper and the lower jaws is called ______ cavity.

thoracic
nasal
hepatic
buccal

The length of ileum is about ______ m.

5
6
7
8

The energy released during cellular respiration is stored in ______.

ATP
glucose
lungs
ileum

The layer of dead cells having tiny openings on the roots is called ______.

root nodule
stomata
chlorenchyma
lenticels

Fish respire through ______.

Gills
spiracles
lungs
skin

In insects the air enters the tracheal system through openings called ______.

spiracles
nostrils
lungs
bronchi

Lungs are situated in ______.

buccal cavity
nasal cavity
thoracic cavity
stomach

Oxidation of glucose takes place in ______.

lungs
heart
mitochondria
chloroplast

The lungs are covered by two membranes called ______.

glottis
pleura
epiglottis
epidermis

The process which releases energy from nutrients is called ______.

respiration
photosynthesis
nutrition
absorption

Which organism shows parasitic mode of nutrition ?

Cascuta
Plasmodium
ascaris
All three

During photosynthesis electrons are released from ______.

Electron Transport System
Chloroplast
Light
All three

During which phase of photosynthesis ATP is used as an energy source ?

Light phase
Light synthetic phase
Biosynthetic phase
Grana phase

During biosynthetic phase carbon dioxide combines with ______.

RuBP
starch
glucose
PGA

Cockroach shows ______ mode of nutrition.

herbivorous
carnivorous
omnivorous
grazing

Gizzard is found in the digestive system of ______.

man
amoeba
locust
earthworm

The function of incisors is ______.

cutting
tearing
grinding
chewing

SHORT QUESTIONS

ANSWER IN SHORT:

Define : Nutrition.

ANS : The process of intake of nutrients and their utilization in every living cell of the body is called nutrition.
What is the aim of the nutrition ?

ANS : The aim of nutrition is to provide energy to the body and help in biosynthesis of body constituents.
Mention two main modes of nutrition.

ANS : Autotrophic nutrition and heterotrophic nutrition are two main modes of nutrition.
From what do autotrophic organisms synthesize glucose and other molecules ?

ANS : Autotrophic organisms synthesize glucose and other molecules from inorganic molecules like carbon dioxide, water and some minerals using solar energy.
What do we mean by autotrophic organisms ?

ANS : Those organisms which can synthesize their own food by using carbon dioxide, water and solar energy are called autotrophic organisms.
What do we mean by heterotrophic organisms ?

ANS : Those organisms which cannot prepare their own food and are dependent on other organisms for nutrition are called heterotrophic organisms.
Mention different types of heterotrophic nutrition.

ANS : The types of heterotrophic nutrition are : saprophytic nutrition, parasitic nutrition and holozoic nutrition.
How is energy derived during heterotrophic nutrition ?

ANS : Energy is derived from the intake and digestion of organic nutrients obtained from plant and animal origin.
Define : Saprophytic nutrition.

ANS : The mode of nutrition in which an organism obtains nutrients from dead and decaying organic matter is called saprophytic nutrition.
Define : Saprophyte

ANS : An organism which obtains nutrition from dead and decaying matter is called a saprophyte.
Define : Parasitic nutrition.

ANS : [TEXT BOOK DEFINITION] If an organism depends on another living organism for nutrition, then this mode of nutrition is called parasitic nutrition.

[PROPER DEFINITION] If an organism obtains nutrition from other organism and in turn harms the latter, the mode of nutrition is called parasitic nutrition.
What is the organism providing food to a parasite called ?

ANS : The organism providing food to a parasite is called 'host'.
Define : Holozoic nutrition.

ANS : The nutrition obtained by the intake of parts of plants or animals or an organism as a whole by the process of ingestion which is then digested and nutrients are absorbed is called holozoic nutrition.
By which process do green plants synthesize food ?

ANS : Green plants synthesize food by photosynthesis.
What does photosynthesis mean ?

ANS : Photosynthesis means synthesis of food with the help of light energy.
Define : Photosynthesis.

ANS : Photosynthesis is a process in which plants (and some micro-organisms) synthesize food from environmental carbon dioxide and water using sunlight and chlorophyll.
Write the chemical equation for photosynthesis.

ANS :

Mention the two phases of photosynthesis.

ANS : The two phases of photosynthesis are (i) Light phase (ii) Biosynthetic phase.
In which form do the chlorophyll molecules absorb light energy ?

ANS : Chlorophyll molecules absorb light energy in the form of photons.
What is photophosphorylation ?

ANS : The synthesis of ATP from ADP and inorganic phosphate during the light phase of photosynthesis is called photophosphorylation.
Write the equation for photolysis of water during photosynthesis.

ANS :

What is the full form of NADP ?

ANS : The full form of NADP is Nicotinamide Adenine Dinucleotide Phosphate.
Where does the light phase of photosynthesis take place in the chloroplast ?

ANS : The light phase of photosynthesis takes place in the grana of chloroplast.
What is formed during the light phase of photosynthesis ?

ANS : ATP and NADPH₂ are formed during the light phase of photosynthesis.
What happens during the biosynthetic phase of photosynthesis ?

ANS : Carbohydrates are formed from carbon dioxide using ATP and NADPH₂ during biosynthetic phase.
Where does the biosynthetic phase take place ?

ANS : Biosynthetic phase takes place in the stroma of the chloroplast.
Who discovered the biosynthetic phase of photosynthesis ?

ANS : Calvin and Benson discovered the biosynthetic phase of photosynthesis.
How does carbon dioxide enter the biosynthetic phase ?

ANS : Carbon dioxide reacts with Ribulose biphosphate (RuBP) and enters the biosynthetic phase.
Mention the factors affecting photosynthesis.

ANS : The factors affecting photosynthesis are : (i) light (ii) water (iii) temperature (iv) carbon dioxide.
What part of visible light is mostly absorbed by chlorophyll ?

ANS : Mostly red and orange region of visible light is absorbed by chlorophyll.
How does the intensity of light affect the rate of photosynthesis ?

ANS : The rate of photosynthesis increases at low intensity and decreases at high intensity.
Why does the low temperature inhibit photosynthesis ?

ANS : Low temperature inhibits the rate of photosynthesis because at low temperatures the activity of the enzymes is lowered.
Why does the rate of photosynthesis decrease at very high temperatures ?

ANS : The rate of photosynthesis decreases at very high temperatures because at those temperatures the enzymes are denatured.
How are animals classified according to their food habit ?

ANS : Animals are classified as herbivores, carnivores and omnivores according to their food habit.
On what does amoeba feed ?

ANS : Amoeba feeds on microscopic plants and animals floating on water.
Mention the processes involved in the nutrition in amoeba.

ANS : The processes involved in the nutrition in amoeba are : ingestion, digestion, assimilation and egestion.
In which parts is the alimentary canal of a grasshopper divided ?

ANS : The alimentary canal of a grasshopper is divided into three parts : (i) foregut (ii) midgut (iii) hindgut.
What forms the foregut of a grasshopper ?

ANS : The foregut of a grasshopper starts from the mouth, followed by a short pharynx, a short and narrow oesophagus, crop and extends upto gizzard.
Which parts does the hindgut of a grasshopper consist of ?

ANS : The hindgut of a grasshopper consists of three parts : (i) an anterior ileum (ii) a middle colon (iii) a posterior rectum.
What are Malphighian tubules ?

ANS : The yellow thread-like minute tubules in the hindgut of a grasshopper are called Malphighian tubules.
What do hepatic caecae do ?

ANS : Hepatic caecae secrete digestive enzymes.
What does the alimentary canal in human digestive system consist of ?

ANS : The alimentary canal in human digestive system consists of mouth, buccal cavity, pharynx, oesophagus, stomach, small intestine, large intestine, rectum and anus.
Mention the accessory digestive glands of human digestive system.

ANS : Salivary glands, liver and pancreas are the accessory digestive glands of human digestive system.
Mention the types of teeth.

ANS : The types of teeth are : (i) incisors (ii) canines (iii) premolars (iv) molars.
What is the posterior region of buccal cavity called ?

ANS : The posterior region of buccal cavity is called pharynx.
Through which valve does the stomach open into duodenum ?

ANS : The stomach opens into duodenum through pyloric valve.
What does the small intestine consist of ?

ANS : The small intestine consists of (i) duodenum (ii) jejunum (iii) ileum.
What is the function of villi in small intestine ?

ANS : The function of villi is to increase the surface area for absorption in small intestine.
Where is the vermiform appendix located ?

ANS : The vermiform appendix is located at the junction of the small intestine and the large intestine.
Define : Inspiration.

ANS : The intake of oxygenated air into lungs is called inspiration.
Define : Expiration.

ANS : The removal of deoxygenated air containing carbon dioxide from the lungs is called expiration.
Define : Breathing.

ANS : The alternate process of inspiration and expiration together is called breathing.
Define : Respiration.

ANS : Respiration is the process involving inspiration and expiration during which every cell of the body receives oxygen and utilises it for oxidation of glucose to release energy.
Define : Aerobic respiration.

ANS : The respiration that takes place in the presence of oxygen is called aerobic respiration.
Why is aerobic respiration also called cellular (internal) respiration ?

ANS : Aerobic respiration is also called cellular (internal) respiration because it takes place within the cell.
Write the chemical equation for aerobic respiration.

ANS :

Define : Anaerobic respiration.

ANS : Respiration which takes place in the absence of oxygen is called anaerobic respiration.
Which organisms exhibit anaerobic respiration ?

ANS : Micro-organisms like bacteria, yeast, fungi and endoparasites exhibit anaerobic respiration.
Mention end products of anaerobic respiration.

ANS : The end products of anaerobic respiration are carbon dioxide and ethanol in plants and lactic acid in the muscles of animals.
Write the chemical equation for anaerobic respiration in plants.

ANS :

Write the chemical equation for anaerobic respiration in muscles.

ANS :[SA-61]
Through what does the gaseous exchange occur between the soil and the inner living cells of plants ?

ANS : The gaseous exchange occurs between the soil and the inner living cells of plants through lenticels.
Through what does the gaseous exchange occur in animals like amoeba/paramoecium ?

ANS : The gaseous exchange occurs through body wall in amoeba/paramoecium.
Gaseous exchange occurs through ______ in earthworm.

ANS : the skin
Through what does the frog respire ?

ANS : The frog respires through skin and lungs.
What is the respiratory organ of insects like locust, housefly and cockroach ?

ANS : Trachea is the respiratory organ of insects like locust, housefly and cockroach.
Through what does the air enter tracheal system in insects ?

ANS : The air enters tracheal system through openings called spiracles in insects.
What type of respiratory surface should be for rapid and efficient gaseous exchange ?

ANS : The respiratory surface should be thin, moist, richly supplied with blood capillaries and in direct contact with the atmosphere for rapid and efficient gaseous exchange.
What does the human respiratory system consists of ?

ANS : Human respiratory system consists of nostrils, nasal cavity, pharynx, larynx, trachea, bronchi and lungs.
What is glottis ?

ANS : Glottis is a slit through which pharynx leads to trachea.
Why does the food not enter the windpipe ?

ANS : The food (during swallowing) does not enter the windpipe because the glottis is covered by a cartilaginous flap of skin called epiglottis.
Name the salivary glands of human digestive system.

ANS : (1) Submendibular salivary gland (2) Sublingual salivary gland
What is the function of canines?

ANS : The function of canines is'tearing' the food particles.

ORGANIC COMPOUNDS -III : LONG ANSWERS

2007-04-07T00:45:00.000-07:00

GIVE ANSWER IN DETAIL

*INDEX-TOPIC SEARCH

Explain : Alcohol group giving common name, IUPAC name and chemical formula of first five compounds.
ANS :

The functional group of an alcohol is -OH.
The general formula of alcohols is C_nH_{2n + 1}OH where C_nH_{2n + 1} is alkyl group (also written as R) and n=1,2,3,...
The suffix "-ane" of an alkane is replaced by "-anol" to give name to the corresponding alcohol. For example : CH₄ is methane and CH₃OH is methanol.
The first five alcohol compounds and their formulas are as follows :

Describe preparation of ethyl alcohol.
ANS : Ethyl alcohol can be prepared by two methods.

Fermentation of carbohydrates
Hydration of ethene

FERMENTATION OF CARBOHYDRATES :

Slow breaking down of carbon compounds in presence of enzymes and in absence of oxygen into simpler compounds is called fermentation.

The sugar (carbohydrates) present in sugarcane, juices of fruits, etc. is first broken down to simple sugars like glucose and fructose by enzyme invertase.

Glucose (and fructose) is converted to ethanol by the enzyme zymase.[Yeast contains both invertase and zymase].

HYDRATION OF ETHENE : Ethene reacts with water in presence of concentrated sulphuric acid to form ethyl alcohol.

Describe chemical properties of ethyl alcohol.
ANS :

Explain : Aldehyde group giving common name, IUPAC name and chemical formula of first four compounds.
ANS : Aldehydes are compounds with -CHO as their functional group.

The IUPAC name of an aldehyde is given by replacing "-ane" of the parent hydrocarbon to "-anal". Thus methane (CH₄) becomes methanal (HCHO) and ethane (C₂H₆) becomes ethanal (CH₃CHO).

The common name, IUPAC name and chemical formula of first four aldehyde compounds are as follows :

Describe preparation, properties and uses of formaldehyde.
ANS :

PREPARATION : Formaldehyde can be prepared by heating methanol to 600 - 700°C in presence of silver oxide as a catalyst. Methanol is oxidised to methanal (formaldehyde).

PHYSICAL PROPERTIES :

Formaldehyde is a colourless gas.
Its boiling point is 20°C.
It is miscible with water.

CHEMICAL PROPERTIES :

   Oxidation : Methanal is oxidised to methanoic acid (formic acid) in presence of oxidising agents like Tollen's reagent, Fehling's reagent, potassium permanganate solution or potassium dichromate solution.

{Note : Tollen's reagent contains silver ammonium ion [Ag(NH₃)₂]⁺ }

   Reduction : In presence of catalyst palladium [Pd], hydrogen reduces methanal to methanol.

   Addition of HCN : Addition of hydrogen cyanide to methanal gives methanal cyanohydrin.

USES :

Formalin (30 - 35 % solution of formaldehyde) is used to preserve biological specimens because it makes proteins insoluble in water.
For the manufacture of polymers like phenol-formaldehyde.

Write an introductory note on carbonyl compounds.
ANS :

The functional group >C=O is known as carbonyl group.
Aldehydes and ketones are carbonyl compounds.
When carbonyl group is attached to at least one hydrogen [i.e.it is attached to either two hydrogen atoms or one hydrogen atom and one alkyl group], an aldehyde compound is obtained.
When carbonyl group is attached to two alkyl groups, a ketone is obtained.

The name of an aldehyde is given by replacing "-ane" from the parent hydrocarbon by "-anal". Example : methane → methanal.
The name of a ketone is given by replacing "-ane" from the parent hydrocarbon by "-anone". Example : propane → propanone.

Describe preparation, properties and uses of propanone (acetone).
ANS :

PREPARATION : Acetone is prepared by 'Fischer and Tropsch' process. When ethene, obtained from the cracking of petroleum, and water gas are mixed and passed over cobalt oxide catalyst at 180°C and 150 atm pressure, propanone is obtained.

PHYSICAL PROPERTIES :

Acetone is a colourless, volatile liquid.
It has a pleasant odour.
It is miscible with water.
Its boiling point is 56°C.

CHEMICAL PROPERTIES :

   Reduction : Propanone reacts with hydrogen in presence of catalysts like sodium boron hydride (NaBH₄) or lithium aluminium hydride (LiAlH₄) to yield 2-propanol.

   Oxidation : Propanone is oxidised to ethanoic acid by alkaline potassium permanganate.

   Addition Reaction With HCN : Acetone reacts with hydrogen cyanide to give acetone cyanohydrin.

USES :

As a nail-polish remover.
In making models, air-plane glue, lacquers, paints, etc.
In leather industry and in artificial fibres.
As a solvent in laboratory.

What are organic acids ? Explain giving example.
ANS :

Organic compounds having -COOH (carboxylic acid) as funcional group are called organic (carboxylic) acids.
Their general formula is C_nH_{2n + 1}COOH where n = 0, 1, 2, 3,...
The suffix "-ane" of parent alkane is replaced by "-anoic" to give the name to an organic acid.
Following table gives common name, chemical name and formula of some organic acids. [Table : 12.4 to be posted- LA-15].

Describe preparation, properties and uses of acetic acid (ethanoic acid).
ANS :

PREPARATION :

   Fermentation : Acetic acid is manufactured by the fermentation of ethyl alcohol with the help of bacteria (acetobacter). Acetic acid obtained by this process is very less and is called 'Vinegar'.

   Chemical Synthesis : The reaction of methanol with carbon monoxide in the presence of catalyst iodine-rhodium (I₂-Rh) gives acetic acid.

PHYSICAL PROPERTIES :

Acetic acid is a colourless liquid.
It has pungent smell.
It is miscible with water.
Its boiling point is 118°C.

CHEMICAL PROPERTIES :

   Reaction With Metals : Acetic acid reacts with metals such as sodium(Na), potassium(K) or magnesium(Mg) and liberates hydrogen.

   Neutralisation : Acetic acid reacts with an alkali (NaOH or KOH) to form respective salt of acetic acid and water.

   Esterification : Acetic acid reacts with alcohols in presence of concentrated sulphuric acid to form ester.

   Decarboxylation : When acetic acid is heated with soda lime (CaO + NaOH) it loses (-COO) part forming methane.

USES :

As vinegar, acetic acid is used as a preservative and taste-enhancer in food (like pickle).
As a laboratory reagent.
As a solvent.
For the preparation of white lead and lead acetate.

Write a note on 'rubber'.
ANS :

Rubber is an addition polymer.
Natural rubber is obtained from the latex of rubber trees.
Natural rubber consists of a long chain of isoprene (monomer) units.

Elasticity of natural rubber is low and is less strong.
Synthetic rubber (neoprene) is obtained by addition polymerization of chloroprene (monomer).
Vulcanisation of Rubber :

Natural rubber becomes brittle below 10°C and melts above 60°C.
Thus, natural rubber is less elastic and less strong.
To make natural rubber more elastic and tough, it is mixed with sulphur powder and heated to 100 to 140°C.
This forms strong links of sulphur between isoprene units.
This process is called vulcanisation of rubber.
Vulcanised rubber is used for making rubber bends, tubes and tyres of vehicles.

Describe preparation of polyester and mention its uses.
ANS : Polyester is prepared by reacting two compounds, one having two carboxylic groups and the other having two hydroxyl groups. This forms a long chain of esters called polyester.

   Uses : Polyester fibres are used in textiles industry along with cotton fibres.

Describe preparation of polyamides (nylon) and mention its uses.
ANS : Polyamides are prepared by reacting two compounds, one having two carboxylic groups and the other having two amide groups. This forms a long chain of amides called polyamides.

   Uses :

As these fibres are strong and waterproof, they are used in making clothes and raincoats.
In making fishing nets and in tyres.

Describe the cleansing action of soaps and detergents.
ANS :

The cleansing actions of soap and detergent are similar.
Both the soap and detergent have two parts in their molecular structure.
The hydrocarbon chain forms nonpolar tail which has no attraction for water but is attracted towards dirt or stains.
The head (negative part) consists of -COONa or SO₃Na group which is polar as it has attraction towards water molecules.
When soap (detergent) solution is applied on the surface having dirt or stain, its nonpolar part is attracted by nonpolar dirt or stain. the polar part remains in water. This type of arrangement around dirt particles is called 'micelle'.
As hydrocarbon part remains attached to dirt or stain and the polar part remains in water, dirt is removed from the surface making it clean and water becomes dirty.

Distinguish between natural rubber and vulcanised rubber.

ANS :

Write a note on fermentation.

ANS :
Fermentation :Fermentation is a slow process of breaking down of carbon compounds in the presence of enzymes and in the absence of oxygen.
Fermentation is used in the manufacture of ethyl alcohol(ethanol) from sugar(carbohydrates). The sugar present in sugarcane, fruit-juices, etc., is first broken down to simple sugars like glucose and fructose by enzyme invertase.
invertase
C₁₂H₂₂O₁₁ + H₂O → C₆H₁₂O₆ + C₆H₁₂O₆
Sugar or molasses glucose fructose

Simple sugars (glucose and fructose) are converted to ethanol by the enzyme zymase.
zymase
C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂
glucose ethanol

Yeast is used in this process because it contains both enzymes invertase and zymase.

[NOTE : The text book defines fermentation as a process taking place in absence of oxygen. While describing the preparation of acetic acid from ethanol, it has been mentioned that Vinegar (ethanoic acid) is formed by oxidation of ethanol in air by acetobactor enzyme through fermentation process. This is an example of one of several controversial issues found in the text book.]

ORGANIC COMPOUNDS -II : BRIEF ANSWERS

2007-04-06T01:48:00.000-07:00

ANSWER IN BRIEF

*INDEX-TOPIC SEARCH

Explain : Functional group.
ANS:

An atom or a group of atoms responsible for the chemical reactions of an organic compound is known as 'Functional Group'.
Functional groups are responsible for the properties of an organic compound.
Functional group is a characteristic of an organic compound.
Examples :

Alcohol (-OH)
Aldehyde (-CHO)
Ketone (>C=O)
Organic acid (-COOH)
Ester (-COOR, R is alkyl part)
-X (halogen, X stands for any of Cl, Br, I, F).

Thus, CH₃CH₂OH (ethanol) is an alcohol and -OH group decides its properties.
All compounds having similar functional group have similar properties.

Write physical properties of ethyl alcohol.
ANS:

Pure ethanol is colourless.
Its boiling point is 78°C.
It is miscible with water.
It is neutral.

Mention uses of ethyl alcohol.
ANS:

As an antiseptic to clean wounds.
To sterilise syringes, gauze, etc.
In alcoholic drinks.
In preparation of rectified spirit (alcohol containing 5% water).
As an industrial solvent.
In preparation of lacquers, varnish and perfumes.

Write about the harmful effects of ethyl alcohol.
ANS:

Person consuming alcohol becomes addict to it.
Eyesight weakens and the person may lose eyesight in the long run.
Ethyl alcohol damages liver and may cause death of the person.
To restrict consumption of ethyl alcohol, some poisonous substance like methanol or CuSO₄ is added to ethanol. This is called 'Denatured Ethyl Alcohol'.

Show that the H atom in the -COOH group has acidic nature.
ANS:The H atom in the -COOH group has acidic nature. The following two reactions are the proof of this.

When acetic acid reacts with a metal like sodium or potassium, hydrogen gas is evolved.

Acetic acid reacts with an alkali to form the respective salt of acetic acid and water.

What is an enzyme ? Write three reactions involving different enzymes.
ANS: An enzyme is a biochemical catalyst which breaks down complex organic molecules into simpler ones. Some reactions involving enzymes are :

Mention the difference between 'Denatured Alcohol' and 'Rectified Spirit'.
ANS:

Ethyl alcohol containing 5% water is called 'rectified spirit'.
Ethyl alcohol containing some poisonous substance like methanol or copper sulphate in small amount is called 'denatured alcohol'.
The purpose of adding poisonous substance is to prevent people from consuming alcohol as its addiction is harmful in the long run.

Explain : Tollen's test.
ANS:
[NOTE : Though this question appears in the list of questions given at the end of the chapter in the text book (GSEB), the description regarding it is given under the title 'ONLY FOR INFORMATION'. Refer to 'Activity 4' in the text book.]

Add sufficient NaOH to a solution of silver nitrate to obtain permanent precipitates.
Dissolve the precipitates in NH₄OH to prepare Tollen's reagent.
Add some aldehyde in the test tube containing Tollen's reagent and place it in a beaker containing water.
Heat the water in the beaker.
The aldehyde will be oxidised and silver (Ag) metal will be liberated. This silver will appear as a mirror on the inner wall of the test tube.

Write addition reactions of formaldehyde and propanone.
ANS: Formaldehyde and propanone show following addition reactions with HCN forming corresponding cyanohydrins.

What is a polymer ? Give its classification.
ANS: A polymer is a long-chain compound with many smaller units called monomers.

Based on their reactions, polymers are classified into (i) Addition polymer and (ii) Condensation polymer.

What are addition polymers ? Give examples.
ANS: Addition polymers are formed by addition of one or more than one (same or different) unsaturated monomer having double or triple bond.

Polythene, PVC, TEFLON, polypropene, natural rubber, polubutadiene and neoprene are addition polymers.

What are condensation polymers ? Give examples.
ANS: A polymer formed by the condensation of two or more than two monomers with the elimination of a simple molecule like water or ammonia is called a condensation polymer.

Polyester, polyamides and phenol-formaldehyde are condensation polymers.

Write a brief note on soap.
ANS: Soaps are sodium or potassium salts of higher fatty acids like stearic or palmitic acid, etc. Soap is in the form of acid, its glycol and ester compounds. The ester compounds are glycerides present in animal fat or vegetable oils. In soaps, -COONa is the functional group attached to the hydrocarbon part.

PREPARATION : On heating vegetable oil or animal fat (esters of higher fatty acids) with sodium hydroxide, sodium salt of fatty acid (soap) and glycerol are formed.

This process is known as Saponification.

Write a note on (Synthetic) Detergents.
ANS:

(Synthetic) Detergents are sodium salts of long-chain sulphonates.
In detergents, -SO₃Na is the functional group attached to hydrocarbon part.
Detergents are superior to soaps as soaps cannot be used with hard water. Soaps form insoluble salts of calcium and magnesium in hard water and cleansing becomes difficult because of Ca⁺² and Mg⁺² ions present in hard water.
Detergents do not form precipitates with these ions. Due to this detergent is used in lesser quantity and its cleansing effect is retained.

Distinguish between soap and detergent.

ANS:

ANS:

ORGANIC COMPOUNDS - I : MCQs & SHORT ANSWERS

2007-04-03T01:04:00.000-07:00

*INDEX-TOPIC SEARCH

MULTIPLE-CHOICE QUESTIONS

SELECT THE CORRECT ALTERNATIVE:

Which of the following is not a functional group containing oxygen ?

Alcohol
Aldehyde
Ketone
Halide

The formula of methanal is ______.

HCHO
CH₃CH₂OH
CH₃COCH₃
CH₃COOCH₃

Which of the following is propanone ?

CH₃OH
CH₃CH₂COOH
CH₃COCH₃
CH₃COOCH₃

The formula of the functional group ester is ______.

-CHO
-COOH
-COOR
-CONH₂

Which of the following represents alcohol group ?

-OH
-COOH
-CHO
-CONH₂

The formula of butanol is ______.

CH₃OH
C₂H₅OH
C₃H₇OH
C₄H₉OH

Fermentation process to manufacture ethyl alcohol is ______.

an aerobic process
an anaerobic process
a polymerization process
a catalytic aerobic process

Which enzyme converts sugar (sucrose) or molasses into glucose or fructose ?

Invertase
Zymase
Ethanol
Ptylin

Which enzyme converts glucose ( or fructose) onto alcohol ?

Ptylin
Invertase
Zymase
Lactose

Yeast contains ______.

invertase only
zymase only
both invertase and zymase
neither invertase nor zymase

Pure ethanol is ______.

acidic
basic
neutral
acidic base

The chemical name of acetic acid is ______.

methanoic acid
ethanoic acid
propanoic acid
vinegar

Ethylethanoate is ______.

an alcohol
an acid
an ester
a ketone

______ have fruity smell.

Alcohols
Organic acids
Esters
Ketones

In aldehydes, the carbonyl group is attached to

one hydrogen and one oxygen
one hydrogen and one alkyl group
two alkyl groups
one oxygen and one alkyl group

The boiling point of formaldehyde is ______°C.

10
20
40
80

Which catalyst is used for the reduction of methanal to methanol.

Pd
Pt
V₂O₅
K₂Cr₂O₇

What is the boiling point of acetone ?

40°C
48°C
56°C
64°C

Which of the following is immiscible with water ?

Ethanol
Formaldehyde
Acetone
Hexane

Oxidation of propanone in presence of alkaline KMnO₄ gives ______.

ethanal
ethanol
ethanoic acid
ethylethanoate

Which of the following is an IUPAC name ?

Propanoic acid
Ethyl alcohol
Formic acid
Acetaldehyde

What is vinegar ?

Methanol
Ethanol
Formic acid
Acetic acid

The boiling point of acetic acid is ______ °C.

98
108
118
128

An organic acid + an alcohol → ______ + water.

An aldehyde
A ketone
An ester
A carboxylic acid

What is used as a food preservative ?

Ethanol
Propanone
Formic acid
Acetic acid

Which of the following is artificial rubber ?

Neoprene
Isoprene
Chloroprene
TEFLON

The monomers of condensation polymer contain minimum ______ functional group/groups.

1
2
3
4

The name of thje functional group -OH is ______.

aldehyde
ketone
alcohol
glucose

Which of the following is the functional group present in ketone compounds ?

-CHO
-OH
C=C
>C=O

Which compound has "-anal" in the end of its name ?

-CHO
-OH
>C=O
C-C

The enzyme which converts milk into curd is ______.

Lactase
Invertase
Zymase
Cellulase

Which of the following is not an oxidising agent ?

NaBH₄
KMnO₄
Cr₂O₃
Fehling's solution

The reaction between carboxylic acid and ethanol in presence of H₂SO₄ is known as ______.

saponification
hydrolysis
esterification
decarboxylation

Which functional group does not give a compound having two carbon atoms ?

Carboxylic acid
Aldehyde
Ketone
Alcohol

Which of the following is a condensation polymer ?

Nylon
PVC
Natural rubber
Teflon

The respsctive aldehyde obtained from methane is ______.

methanol
formic acid
formaldehyde
ethanol

5% aquaous solution of ethanol is known as...

formalin
vinegar
denatured alcohol
rectified spirit

Tollen's reagent is...

Ammoniacal silver nitrate
Silver nitrate
Ammonium nitrate
Ammonium chromate

Which gas is produced during fermentation ?

CO
CO₂
Cl₂
O₂

ANSWERS TO MCQs

(1) D (2) A (3) C (4) C (5) A (6) D (7) B (8) A (9) C (10) C (11) C (12) B (13) C (14) C (15) B (16) B (17) A (18) C (19) D (20) C (21) A (22) D (23) C (24) C (25) D (26) A (27) B (28) C (29) D (30) A (31) A (32) A (33) C (34) C (35) A (36) C (37) D (38) A (39) B (40)

SHORT QUESTIONS

ANSWER IN SHORT:

What are hydrocarbons ?

ANS : The compounds containing atoms of carbon and hydrogen only are called hydrocarbons.

What is a functional group ?

ANS : An atom or a group of atoms which is responsible for chemical reactions of organic compounds is called a functional group. OR An atom or a group of atoms present in a compound which is responsible for the chemical properties of that compound is called a functional group.

Organic compounds containing same functional group show similar chemical properties. True or false ?

ANS : This is a true statement.

Ethane reacts more rapidly than ethyne. True or false ?

ANS : This is a false statement.

What is the general formula of alcohols ?

ANS : The general formula of alcohols is C_nH_{2n + 1}OH or R-OH where R represents the alkyl group (C_nH_{2n + 1}) and n=1,2,3,...

Write the formula of ethanoic acid.

ANS : The formula of ethanoic acid is CH₃COOH.

Mention first four alkanes.

ANS : Methane, ethane, propane and butane are first four alkanes.

Mention first four alcohols.

ANS : Methanol, ethanol, propanol and butanol are first four alcohols.

By which two methods can ethyl alcohol (ethanol) be prepared ?

ANS : Ethyl alcohol can be prepared by (i) Fermentation of carbohydrates (ii) Hydration.

Which enzyme converts milk into curd ?

ANS : Lactase converts milk into curd.

What does lactase do during the conversion of milk into curd ?

ANS : Lactase converts lactose into lactic acid.

What is fermentation ?

ANS : Fermentation is a slow process of breaking down of carbon compounds in the presence of enzymes amd in the absence of oxygen.

Write the reaction of hydration of ethene.

ANS :

What is the boiling point of pure ethanol ?

ANS : The boiling point of pure ethanol is 78°C.

Write the equation for the combustion of ethanol.

ANS :

Write the formula of sodium ethoxide.

ANS : The formula of sodium ethoxide is CH₃CH₂ONa.

What is obtained when ethanol reacts with sodium metal ?

ANS : When ethanol reacts with sodium metal; sodium ethoxide and hydrogen are obtained.

What is the formula of ethanal ?

ANS : The formula of ethanal is CH₃CHO.

What is the formula of ethylethanoate (ethyl acetate) ?

ANS : The formula of ethylethanoate is CH₃COOCH₂CH₃.

Write the IUPAC name of CH₃C₂H₅.

ANS : Ethylethanoate.

What is esterification ?

ANS : The process in which an alcohol reacts with an organic acid to form an ester in presence of a small amount of conc. sulphuric acid is called Esterification.

What is 'rectified spirit' ?

ANS : Ethyl alcohol containing 5% water is called 'rectified spirit'.

What is 'Denatured' ethyl alcohol ?

ANS : 'Denatured' ethyl alcohol is the ethyl alcohol to which poisonous methanol or CuSO₄ has been added to prevent people from consuming it.

Write symbolically the functional group 'carbonyl'.

ANS : The functional group carbonyl is >C=O.

Write the formula of formaldehyde (methanal).

ANS : The formula of formaldehyde is

Write the formula of acetone.

ANS : The formula of acetone (propanone) is

Write the common as well as IUPAC name of the compound whose formula is HCHO.

ANS : The common name of HCHO is formaldehyde and its IUPAC name is methanal.

Write the common names of first four aldehyde compounds.

ANS : The common names of first four aldehyde compounds are : formaldehyde, acetaldehyde, propionaldehyde and butyraldehyde.

Write the chemical formula of butanal.

ANS : The chemical formula of butanal is CH₃CH₂CH₂CHO.

Write the common name of methanal and propanone.

ANS : The common name of methanal is formaldehyde and that of propanone is aceton.

Which catalyst is used to prepare formaldehyde from methanol ?

ANS : Silver oxide, Ag₂O is used as catalyst to prepare formaldehyde from methanal

Write the chemical equation of oxidation of methanol to methanal.

ANS :

What does oxidation of methanal yield ?

ANS : The oxidation of methanal yields methanoic acid.

Mention the oxidising agents used for the oxidation of methanal.

ANS : Tollen's reagent, potassium permanganate solution, solution of potassium dichromate, etc rae used as oxidising agents for the oxidation of methanal.
[The Gujarati version of text book (GSEB) mentions two names : Ammoniacal silver nitrate (Tollen's reagent) and Fehling's reagent].

Write the chemical formula of methanal cyanohydrin.

ANS : The formula of methanal cyanohydrin is

What is formalin ?

ANS : Formalin is 30-35 % aqueous solution of formaldehyde.

Name the process by which acetone (propanone) is prepared.

ANS : Acetone is prepared by Fischer-Tropsch process.

Which catalyst is used in Fischer-Tropsch process to prepare acetone ?

ANS : Cobalt oxide (CoO) is used as catalyst in Fischer-Tropsch process to prepare acetone.

What is the formula of iso-propyl alcohol (2-propanol) ?

ANS : The formula of iso-propyl alcohol is

What is the formula of acetone cyanohydrin ?

ANS : The formula of acetone cyanohydrin is

Write the general formula of carboxylic acid (organic acids).

ANS : The general formula of carboxylic acids is
C_nH_{2n + 1}COOH [n=0,1,2,3,...].

What is the common name of methanoic acid ?

ANS : The common name of methanoic acid is formic acid.

Which bacteria convert ethanol into acetic acid ?

ANS : Acetobactor convert ethanol into acetic acid.

Which catalyst is used in the preparation of acetic acid from methanol.

ANS : I₂-Rh (Iodine-rhodium) is used as a catalyst in the preparation of acetic acid from methanol.

Acetic acid is immiscible with water. True or false ?

ANS : This is a false statement.

Write the equation showing reaction between acetic acid and sodium metal.

ANS :

What is neutralisation reaction ?

ANS : A neutralisation reaction is the one in which an acid reacts with a base to form a salt and water.

Give the example of the neutralisation reaction of acetic acid.

ANS :

CH₃COOH + NaOH → CH₃COONa + H₂O
.

What is sodalime ?

ANS : Sodalime is a mixture of NaOH and CaO in the ratio of 3:1 (NaOH + CaO).

What is produced when acetic acid reacts with sodalime ?

ANS : Methane and carbon dioxide are produced when acetic acid reacts with sodalime.

What is decarboxylation reaction ?

ANS : The removal of carbon dioxide (-COO part) from the carboxyl group of an organic acid is called decarboxylation reaction.

What is vinegar ?

ANS : Vinegar is 4 to 6 % aqueous solution of acetic acid.

What do we mean by man-made materials ?

ANS : New substances prepared from the natural raw materials are called man-made materials.

What are polymers ?

ANS : Polymers are long-chain compounds with many smaller units called monomers.

Mention some synthetic fibres.

ANS : Rayon, nylon, polyester, etc. are synthetic fibres.

Give some examples of plastics.

ANS : Polythene, polyvinylchloride (PVC), TEFLON, Bakelite, melamine, etc. are examples of plastics.

How rae polymers classified ?

ANS : Polymers are classified on the basis of the reaction of their formation into 'Addition polymer' and 'Condensation polymer'.

What is the chemical name of TEFLON ?

ANS : The chemical name of TEFLON is Polytetrafluoroethene.

What is an addition polymer ?

ANS : Addition polymers are formed by addition of one or more than one (same or different) unsaturated monomer having double or triple bond.

Mention monomers of natural rubber and artificial rubber.

ANS : Isoprene is the monomer of natural rubber and chloroprene is the monomer of artificial rubber.

Write the formula of isoprene.

ANS : The formula of isoprene is

Write the formula of butadiene.

ANS : The formula of butadiene is CH₂=CH-CH=CH₂.

What is used as an alternative to rubber ?

ANS : Polybutadiene is used as an alternative to rubber.

What is the formula of chloroprene ?

ANS : The formula of chloroprene is

Give examples of addition polymers.

ANS : Polythene, PVC, rubber, polybutadiene, etc. are examples of addition polymers.

From what is natural rubber obtained ?

ANS : Natural rubber is obtained from the latex of rubber trees.

What are the defects of natural rubber ?

ANS : Natural rubber has low elasticity and low strength (it is less tough).

Between which temperature range is the elasticity of natural rubber maintained ?

ANS : The elasticity of natural rubber is maintained between 10°C to 60°C.

What is the effect of temperature on natural rubber ?

ANS : Natural rubber becomes brittle below 10°C and soft above 60°C.

What is vulcanisation of rubber ?

ANS : Vulcanisation of rubber is the process in which rubber is mixed with sulphur powder and heated upto 100 - 140°C.

Why is rubber vulcanised ?

ANS : Rubber is vulcanised to improve its properties of elasticity and hardness.

What is a condensation polymer ?

ANS : A polymer formed by the condensation of two or more than two monomers with the elimination of a simple molecule like water or ammonia, is called condensation polymer.

Give examples of condensation polymer.

ANS : Polyester and polyamides are examples of condensation polymer.

Which types of compounds react to form polyester ?

ANS : A compound containing two carboxylic acid groups and another compound containing two hydroxyl groups react to form polyester.

Which types of compounds react to form polyamides ?

ANS : A compound containing two carboxylic acid groups and another compound containing two amino groups react to form polyamides.

Nylon is an addition polymer. True or false ?

ANS : This is a false statement.

Nylon is a polyamide. True or false ?

ANS : This is a true statement.

What is soap ?

ANS : Soap is a sodium or potassium salt of higher fatty acids like stearic acid or palmitic acid.

What is saponification ?

ANS : saponification is a process of making soap by reaction between a vegetable oil and sodium hydroxide.

What are (synthetic) detergents chemically ?

ANS : Chemically detergents are sodium salts of sulphonates.

Mention the functional groups of soap and detergent.

ANS : The functional group of a soap is -COONa and that of a detergent is -SO₃Na.

Which are two parts of a soap or detergent ?

ANS : A long chain of hydrocarbon which is nonpolar and water-repelling and -COONa (in soap) or -SO₃Na (in detergent) which is polar and has affinity for water are the two parts of a soap or detergent.

Which functional group is present in the following compounds ? (i)CH₃CH₂CH₂OH (ii) CH₃COCH₃ (iii) CH₃CHO (iv) CH₃CH₂COOH (v) CH₃CH₂CH=CH₂.

ANS : (i) Alcohol (ii) ketone (iii) aldehyde (iv) carboxylic acid (v) hydrogen.

Which gas is produced during the process of fermentation ?

ANS : Carbon dioxide gas is produced during the process of fermentation.

Which compound is obtained during the hydration of ethene ?

ANS : Ethyl alcohol is obtained during the hydration of ethene.

Write the names of products of oxidation reaction of ethanol in presence of KMnO₄ and chromium oxide.

ANS : The product obtained by oxidation of ethanol in presence of KMnO₄ is ethanoic acid whereas in presence of chromium oxide we get ethanal.

Write the equation of the reaction of reduction of methanal.

ANS :

What is obtained as by-product during preparation of soap ?

ANS : Glycerol is obtained as by-product during preparation of soap.

How can you convert propanone to ethanoic acid ?

ANS : Propanone can be converted to ethanoic acid by its oxidation using alkaline potassium permanganate.

Define detergent.

ANS : A chemical substance used to remove dirt from the surface of anything is called a detergent.

What are glycerides ?

ANS : Glycerides are ester compounds present in animal fat or vegetable oils.

Which two enzymes are present in yeast ?

ANS :Invertase and zymase are two enzymes present in yeast.

NON-METALS - III : LONG ANSWERS

2007-03-28T10:20:00.000-07:00

GIVE ANSWER IN DETAIL

*INDEX-TOPIC SEARCH

Mention physical properties of nonmetals.
ANS :

Nonmetals occur in all three states : solid, liquid and gas.
They are neither malleable nor ductile.
They do not conduct heat and electricity because they do not have free electrons (graphite is an exception).
They are lustreless.
They are hard and brittle.
They generally have low melting points and boiling points.
They are light in weight.
Solid nonmetals do not produce ringing sound.

Explain chemical properties of nonmetals.
ANS : Nonmetals are electronegative elements because they accept electrons and form negatively charged ions. For example, oxygen forms negative oxide ion O^-2 by accepting two electrons.
1/2 O₂ + 2 e^- → O^-2
1/2 Cl₂ + e^- → Cl^-

REACTION WITH OXYGEN : Nonmetals form either acidic oxide or neutral oxide with oxygen.

When carbon burns in air, it forms carbon dioxide which is an acidic oxide.
C_(s) + O_2(g) → CO_2(g)

Carbon dioxide dissolves in water to form carbonic acid [H₂CO₃].
CO_2(g) + H₂O_(l) → H₂CO_3(aq)

When sulphur burns in air, it reacts with oxygen to form sulphur dioxide which is an acidic oxide.
S_(s) + O_2(g) → SO_2(g)

Sulphur dioxide dissolves in water to form sulphurous acid [H₂SO₃]
SO_2(g) + H₂O_(l) → H₂SO_3(aq)

Phosphorus forms phosphurus pentoxide (2P₂O₅) with oxygen which dissolves in water to form phosphoric acid [H₃PO_4(aq)].
P_4(s) + 5O_2(g) → 2P₂O_5(g)

2P₂O_5(g) + 6H₂O → 4H₃PO_4(aq)

Oxides like CO, N₂O, H₂O are neutral oxides as their aqueous solutions are neither acidic nor basic or they do not have any effect on any litmus paper.

REACTION WITH ACIDS : Nonmetals do not react with dilute acids as they are not able to displace hydrogen from acids.

REACTION WITH CHLORINE : Nonmetals form chlorides with chlorine. These chlorides are either liquid or gas.

REACTION WITH HYDROGEN : Nonmetals form covalent hydrides with hydrogen.

Methane (CH₄), hydrochloric acid (HCl), etc. are hydrides of nonmetals.

Describe the Importance of nonmetals.
ANS :

Hydrogen gas reacts with nitrogen to form ammonia gas.
Carbon is used in the preparation of useful substances like gunpowder, sugar, cold drinks, dry ice, urea, etc.
Oxygen supports life on earth.
Nitrogen is used in the preparation of nitric acid, nitroglycerin(explosives) and nitrogenous fertilisers.
Sulphur is used in the preparation of paper pulp, fungicides, etc.
Phosphorus is used in making matchsticks, insecticides, etc.

Write a few sentences on Hydrogen.
ANS :

Hydrogen was discovered in 1766 AD by English chemist Cavendish.
Its chemical symbol is H.
It is the lightest of all elements.
It is the first element of the periodic table.
Hydrogen does not occur in free state (monoatomic molecule) in the atmosphere.
It is a diatomic molecule.
it is a colourless, odourless gas.
It is present in outer space.
It is the main element present in sun.

Describe preparation of hydrogen in laboratory.
ANS :

AIM : To prepare hydrogen gas in laboratory.

APPARATUS & MATERIAL : Conical flask, Thistle funnel, glass container, bee-hive shelf, glass jar, glass tube, zinc granules, hydrochloric acid, water, etc.

PROCEDURE :

Zinc granules are taken in conical flask and the equipment is set up as shown in figure.
Dilute hydrochloric acid is added slowly to the flask through thistle funnel.

OBSERVATION : The reaction between zinc granules and dilute hydrochloric acid produces hydrogen gas which is collected by downward displacement of water in an inverted jar.

CHEMICAL REACTION :

Zn_(s) + 2HCl_(aq) → ZnCl_2(aq) + H_2(g)

NOTE : In place of dilute HCl we can also use dilute H₂SO₄.

Zn_(s) + H₂SO_4(aq) → ZnSO_4(aq) + H_2(g)

Describe manufacture of hydrogen from natural gas.
ANS :

Hydrogen gas is manufactured on large scale from natural gas by steam reforming process.
Methane (the main constituent of natural gas) is mixed with steam and passed over nickel catalyst at 800°C and 30 atm pressure.
The reaction produces carbon dioxide and hydrogen.

Hydrogen gas can also be obtained by the electrolysis of acidified water.

Describe chemical properties of hydrogen.
ANS :

Hydrogen gas burns in air (oxygen) with a blue flame forming watervapour.

2H_2(g) + O_2(g) → 2H₂O_(g)

It burns in chlorine to form white fumes of hydrogen chloride gas.

H_2(g) + Cl_2(g) → 2HCl_(g)

Similarly it forms hydrogen fluoride gas with fluorine.

H_2(g) + F_2(g) → 2HF_(g)

It forms hydrides with metals like lithium, sodium and calcium.

H_2(g) + 2Li_(s) → 2LiH_(s)

H_2(g) + 2Na_(s) → 2NaH_(s)

H_2(g) + Ca_(s) → CaH_2(s)

Hydrogen reduces oxides of those metals, which are less reactive, to free metals. Thus, when hydrogen is passed over hot copper oxide copper metal and water are produced.

CuO_(s) + H_2(g) → Cu_(s) + H₂O_(l)

Write a detailed note on ammonia, its manufacture, properties and uses.
ANS :
AMMONIA : Ammonia is a very important industrial chemical as it is used for the manufacture of a wide range of chemicals. It is manufactured commercially by Haber's process.

MANUFACTURE : A mixture of nitrogen and hydrogen in the ratio of 1 : 3 is heated under 200 - 300 atm pressure in presence of catalyst (finely divided iron + molybdenum) at about 450 °C. The reaction is reversible.

PHYSICAL PROPERTIES :

It is a colourless gas.
It has characteristic pungent smell which irritates eyes and nose.
It is poisonous.
It is highly soluble in water.

CHEMICAL PROPERTIES :

Ammonia reacts with hydrochloric acid to form ammonium chloride.

NH_3(g) + HCl_(l) → NH₄Cl_(s)

Ammonia decomposes in presence of electric discharge.

Ammonia reacts with oxygen in presence of catalyst platinum at 1073 K to form nitric oxide.

Aqueous solution of ammonia acts as a base. [NOTE : This property is given as physical property in the text book]

USES :

In the manufacture of fertilisers such as urea, ammonium nitrate and ammonium sulphate.
In the manufacture of nitric acid.
In the manufacture of baking soda and washing soda.
In the manufacture of some medicines such as para-aminobenzoic acid (PABA), folic acid, etc.
In the preparation of dyes and explosives.

Describe Extraction of Sulphur.
ANS : Pure sulphur is obtained by (i)Frasch Process or (ii) from natural gas and oil by chemical process.

FRASCH PROCESS : The process is used to obtain pure sulphur from the sulphur bed in the ground. It is based on the fact that sulphur has relatively low melting point.

A hole of about 30 cm diameter is bored upto the sulphur bed.
Three concentric pipes of different diameters are descended upto sulphur deposits.
Pressurised superheated water at about 170°C is forced down through the outermost pipe. The heat of water melts the underground sulphur.
Hot compressed air is passed through the innermost pipe.
A mixture of molten sulphur and water comes out through central pipe.
The sulphur-water emulsion is allowed to settle in settling tanks. Yellow solid sulphur separates from water after cooling. This sulphur is 99.5% pure.

FROM NATURAL GAS AND OIL :

Sulphur compounds in natural gas and oil are first converted into hydrogen sulphide. (H₂S).
Hydrogen sulphide is heated in presence of oxygen to obtain sulphur dioxide.
This sulphur dioxide is then heated with additional hydrogen sulphide in the presence of catalyst Fe₂O₃ to obtain sulphur in free state.

Write a note on Allotropes of sulphur.
ANS :

Different arrangement of molecules in the crystals give rise to allotropes of sulphur.
There are two allotropes of crystalline sulphur. (i)Rhombic sulphur and (ii) Monoclinic sulphur.
Rhombic sulphur is stable below 96°C and its crystals have octahedral shape.
Monoclinic sulphur is stable above 96°C and its crystals are needle-shaped.
As one allotrope changes into another at 96°C, it is called TRANSITION TEMPERATURE for sulphur.
Both allotropes have similar chemical properties but their physical properties differ due to their different physical structures.
When solid sulphur is heated its molecular chain breaks which on further heating yields viscous liquid sulphur. This on heating starts boiling.

Mention Chemical properties of sulphur.
ANS :

Sulphur burns with blue flame and produces sulphur dioxide.

S_(s) + O_2(g) → SO_2(g)

REACTION WITH ACIDS : Sulphur is oxidised to sulphur dioxide when it reacts with hot and concentrated sulphuric acid.

S_(s) + 2 H₂SO_4(aq) → 2H₂O_(l) 3SO_2(g)

Sulphur is oxidised to sulphuric acid when it reacts with hot and concentrated nitric acid.

S_(s) + 6HNO_3(aq) → H₂SO_4(aq) + 6NO_2(g) + 2H₂O_(g)

REACTION WITH CARBON : Sulphur reacts with carbon at high temperature to give carbon disulphide.
C_(s) + 2S_(s) → CS_2(l)

REACTION WITH HYDROGEN : When hydrogen gas is passed through boiling sulphur, foul smelling hydrogen sulphide gas is formed.
S_(s) + H_2(g) → H₂S_(g)

Mention uses of sulphur.
ANS :

In the manufacture of sulphuric acid.
As an antiseptic in skin ointments for skin treatment and in cosmetics.
For making dyes, matches, gunpowder, pulp of paper and fireworks.
In vulcanisation of rubber.
For manufacturing carbon disulphide which is a solvent.
As a disinfectant, fungicide, germicide, etc. for destroying bacteria, fungi, insects, etc.
In printing (dyeing) of clothes.

Write a detailed note on sulphur dioxide.
ANS : The reaction of sulphur with oxygen gives sulphur dioxide.

S_(s) + O_2(g) → SO_2(g)

PHYSICAL PROPERTIES :

It is a colourless gas.
It has a pungent smell.
It is a pollutant gas which causes acid rain due to dissolution in rain water.

CHEMICAL PROPERTIES :

Sulphur dioxide dissolves in water to form sulphurous acid (H₂SO₃).

SO_2(g) + H₂O_(l) ↔ H₂SO_3(aq)

Sulphur dioxide reacts with aqueous sodium hydroxide to form sodium sulphite (Na₂SO₃).
SO_2(g) + 2NaOH_(aq) → Na₂SO_3(aq) + H₂O_(l)

When sulphur dioxide gas is passed through lime-water, the solution turns cloudy due to the formation of insoluble calcium sulphite (CaSO₃).

SO_2(g) + Ca(OH)_2(aq) → CaSO_3(s) + H₂O_(l)

When sulphur dioxide gas is passed through an aqueous solution of hydrogen sulphide, it turns milky (turbid) due to formation of colloidal sulphur.

SO_2(g) + 2H₂S_(aq) → 3S_(s) + 2H₂O_(l)

Sulphur dioxide combines with oxygen in presence of catalyst vanadium pentoxide [V₂O₅] at 450°C to form sulphur trioxide.

USES :

For the manufacture of sulphuric acid.
As a preservative in orange and lemon squashes and jams.
For bleaching of wood pulp in paper industry.

Describe manufacture of sulphuric acid by Contact Process.
ANS : The contact process is divided into different stages and uses various units such as sulphur burner, precipitator, steam scrubber, drying tower, arsenic purifier, contact chamber and absorption unit.

PREPARATION OF SO₂ : SO₂ is obtained by burning sulphur or pyrites.
Δ
S_(s) + O_2(g) → SO_2(g)

CONVERSION OF SO₂ into SO₃ IN CONTACT CHAMBER : The mixture of purified SO₂ and air is passed over catalyst vanadium pentoxide [V₂O₅] to produce SO₃.

ABSORPTION OF SO₃ IN CONC. H₂SO₄ : SO₃ obtained from the contact chamber is dissolved in concentrated H₂SO₄ acid giving oleum, H₂S₂O₇. [Oleum is also known as 'fuming sulphuric acid'.]

Sulphuric acid of any concentration can be obtained by diluting oleum with water.

H₂S₂O_7(l) + H₂O_(l) → 2H₂SO_4(aq)

Contact process yields sulphuric acid which is pure and of about 100% strength.

Write physical properties, chemical properties and uses of sulphuric acid.
ANS :
PHYSICAL PROPERTIES

Concentrated sulphuric acid is colourless viscous liquid containing 98% H₂SO₄ and 2% water.
Concentrated sulphuric acid is a powerful water-absorbing agent.
Dilute sulphuric acid contains 10% H₂SO₄ and 90% water.

CHEMICAL PROPERTIES

Concentrated sulphuric acid dehydrates sugar to carbon. The black mass of carbon is called sugar charcoal and the reaction is called charring of sugar.

Dilute sulphuric acid reacts with metals like zinc and iron to form metal sulphates and hydrogen gas.

Zn_(s) + H₂SO_4(aq) → ZnSO_4(aq) + H_2(g)

Fe_(s) + H₂SO_4(aq) → FeSO_4(aq) + H_2(g)

Sulphuric acid is strong dibasic acid from which two hydrogen atoms can be displaced in solution.

H₂SO_4(l) + 2H₂O_(l) → 2H₃O⁺_(aq) + SO_4(aq)^-2

USES

In the preparation of fertilisers.
In the manufacture of pigments, dyes and paints.
In the preparation of detergents.
In storage batteries.

ANS :

NON-METALS - II : BRIEF ANSWERS

2007-03-28T00:53:00.000-07:00

ANSWER IN BRIEF

*INDEX-TOPIC SEARCH

Explain with example : Reaction of nonmetals with chlorine.
ANS: Nonmetals form chlorides with chlorine. These chlorides are usually in gaseous state.

Explain with example : Reaction of nonmetals with hydrogen.
ANS: Nonmetals form covalent hydrides with hydrogen.

Methane (CH₄), hydrochloric acid (HCl), etc. are hydrides of nonmetals.

Mention physical properties of hydrogen.
ANS:

It is lighter than air.
It is a colourless, tasteless and odourless gas.
It is insoluble in water.
It is neutral gas (it does not change the colour of litmus paper).

Mention uses of hydrogen.
ANS:

Hydrogen Welding : When an electric arc is passed through hydrogen, it splits into atoms which release large amount of heat when they recombine to form molecules. This heat is used to melt and join (weld) the metals.
In the manufacture of ammonia by Haber's process.
In the manufacture of methanol and hydrochloric acid.
Liquid hydrogen is used as a fuel in space shuttles.
In the manufacture of vegetable ghee.

Mention physical properties of sulphur.
ANS:

It is pale yellow solid crystalline substance which exists in different forms called allotropes.
It is odourless and tasteless.
It is insoluble in water.
It is soluble in organic solvents like carbon disulphide, toluene (methyl
benzene), etc.

ANS:

NON-METALS - I : MCQs & SHORT ANSWERS

2007-03-25T08:16:00.000-07:00

*INDEX-TOPIC SEARCH

MULTIPLE-CHOICE QUESTIONS

SELECT THE CORRECT ALTERNATIVE:

There are ______ nonmetals.

20
22
24
25

How many nonmetals are in solid state ?

11
12
13
14

How many nonmetals are in gaseous state ?

7
8
9
10

The atomic number of sulphur is...

15
16
17
18

Which of the following is used as a fuel in space rockets ?

Liquid hydrogen
Liquid nitrogen
Refined kerosene
phenol

Sulphur belongs to _____ group in periodic table.

Boron
Carbon
Oxygen
Halogen

_____ ia a metalloid.

Copper
Sodium
Bromine
Silicon

When sulphur reacts with sulphuric acid _____ gas is produced.

SO₂
H₂S
NO₂
NH₃

Sulphuric acid is produced by ______.

Ostwald process
Frasch process
Contact process
Bessemer process

ANSWERS TO MCQs

(1) B (2) A (3) D (4) B (5) A (6) C (7) D (8) A (9) C (10)

SHORT QUESTIONS

ANSWER IN SHORT:

Which nonmetal is in liquid state ?

ANS : Bromine is the nonmetal in liquid state.

Give an example of a nonmetal which conducts heat and electricity.

ANS : Graphite ( a form of carbon) conducts heat and electricity.

Why are nonmetals electronegative elements ?

ANS : Nonmetals are electronegative elements because they accept electrons and form negatively charged ions.

Which type of oxides do nonmetals form ?

ANS : Nonmetals form either acidic or neutral oxides.

Write formula of carbonic acid.

ANS : The formula of carbonic acid is H₂CO₃.

Give examples of some neutral oxides.

ANS : CO, N₂O, H₂O are examples of neutral oxides.

Why is carbon monoxide a neutral oxide ?

ANS : Carbon monoxide (CO) is a neutral oxide because it forms neither acid nor base with water.

Why do nonmetals not react with dilute acids ?

ANS : Nonmetals do not react with dilute acids because they are not able to displace hydrogen from acids.

Who discovered hydrogen ? When ?

ANS : English chemist Cavendish discovered hydrogen in 1766 AD.

Why is ammonia a very important chemical ?

ANS : Ammonia is a very important chemical because it is used in the preparation of fertilisers, nitric acid, explosives, nylon fibre, etc as well as household cleaners.

Why is ammonia not collected by downward displacement of water ?

ANS : Ammonia is not collected by downward displacement of water because it is highly soluble in water.

What is the full form of PABA ?

ANS : The full form of PABA is Para-Amino Benzoic Acid.

Mention important ores of sulphur.

ANS : Important ores of sulphur are : Zinc blende (ZnS), gypsum (CaSO₄.2H₂O) and copper pyrites (CuFeS₂).

Write electronic configuration of sulphur ?

ANS : The electronic configuration of sulphur is 2,8,6.

When SO₂ is heated with H₂S in the presence of catalyst ______, sulphur is obtained. [Fill up the blank].

ANS : Fe₂O₃.

Mention two crystalline allotropes of sulphur.

ANS : The crystalline allotropes of sulphur are (1) rhombic sulphur (2) monoclinic sulphur.

What is transition temperature ?

ANS : The temperature at which one allotrope of an element changes into another allotrope is called TRANSITION TEMPERATURE of that element.

What is the transition temperature of sulphur ?

ANS : The transition temperature of sulphur is 96°C.

What is the shape of the crystals of rhombic sulphur ?

ANS : The shape of the crystals of rhombic sulphur is octahedral.

What is the shape of the crystals of monoclinic sulphur ?

ANS : The shape of the crystals of monoclinic sulphur is needle-like.

What is known as the king of chemicals ?

ANS : Sulphuric acid is known as the king of chemicals.

Why is sulphuric acid known as the king of chemicals ?

ANS : Sulphuric acid is known as the king of chemicals because it is used to prepare many important chemical substances like fertilisers, dyes, soap, etc.

Which catalyst is used for conversion of SO₂ into SO₃ in contact chamber ?

ANS : V₂O₅ is used as catalyst for conversion of SO₂ into SO₃ in contact chamber.

What is the strength of H₂SO₄ obtained by Contact process ?

ANS : The strength of H₂SO₄ obtained by Contact process is about 100 %.

What is charring of sugar ?

ANS : The process in which concentrated sulphuric acid converts sugar to a black mass of carbon (sugar charcoal) by dehydration is called charring of sugar.

Give names of some nonmetallic elements.

ANS : Hydrogen, oxygen, nitrogen, chlorine, bromine, iodine, sulphur, phosphorus, etc. are nonmetallic elements.

Write an equation for the reaction of phosphorus pentoxide with water.

ANS :
2P₂O_5(g) + 6H₂O_(l) → 4H₃PO_4(aq)

Write the equation for the industrial production of hydrogen.

ANS :
Ni catalyst
800°C
30 atm
CH_4(g) + 2H₂O -----> CO_2(g) + 4H_2(g)

By which method is ammonia gas produced ?

ANS : Ammonia gas is produced by Haber's process.

Which nonmetallic element is obtained by Frasch process ?

ANS : Sulphur is obtained by Frasch process.

Write chemical formula of Oleum (fuming sulphuric acid).

ANS : The chemical formula of fuming sulphuric acid is H₂S₂O₇.

Which crystalline form of sulphur is most stable ?

ANS : Rhombic sulphur is the most stable crystalline form of sulphur.

On which physical property of sulphur is Frasch process based ?

ANS : Frasch process is based on the property of low melting point (388 K) of sulphur.

ANS :

METALS - III : LONG ANSWERS

2007-03-22T09:52:00.000-07:00

GIVE ANSWER IN DETAIL

*INDEX-TOPIC SEARCH

Write a note on minerals in India.

ANS : [table to be posted]

Explain : Froth Floatation Process OR The process to concentrate sulphide ores.

ANS : This method is used for the concentration of sulphide ores of copper, zinc, lead, etc.

PRINCIPLE: This method is based on the principle of difference in the wetting properties of the ore and the gangue particles with water and oil.

PROCESS:

The powdered ore is mixed with water, containing small quantity of oil (pine oil or turpentine oil) in a large tank.
The sulphide particles in the ore get wet with oil while dust and sand particles do not get wet with oil.
The water containing ore is agitated violently by blowing air to form froth.
Sulphide particles being lighter float along with the froth at the surface which is removed from the top of the tank and collected.
Impurities being heavier collect at the bottom. The froth is then washed, filtered and dried.

Write a note on Magnetic Separation.

ANS :

PRINCIPLE:This method uses the principle of difference in the magnetic properties of the ore and the gangue (impurities).

EQUIPMENT:

A magnetic separator consists of a leather conveyer belt moving over two rollers. One of the rollers has a strong magnet in it.

PROCESS: Powdered ore is dropped on the moving belt at one end through a hopper. When it reaches the other end , nonmagnetic impurities fall down first whereas the magnetic particles fall later forming a separate heap.

This method is generally used for the concentration of iron ores.

Explain : Calcination with proper examples.

ANS : Calcination is a process in which concentrated ore is heated strongly in absence of air. Calcination is generally used
for conversion of metal carbonates and hydroxides in to their corresponding oxides and to remove volatile impurities.

Examples:

Write a note on 'Chemical Reduction' method.

ANS : The conversion of metal oxide into metal is called REDUCTION. When chemicals like carbon, carbon monoxide, aluminium, etc. are used as reducing agents, the process is called CHEMICAL REDUCTION.
In the carbon-reduction process, the metal oxide is mixed with coke (a form of carbon) and heated in a furnace. Carbon reduces metal oxide to free metal. Oxides of zinc, iron, copper, nickel, tin and lead are reduced by this method.

    ZnO_(s) + C_(s) → Zn_(s) + CO_(g)

    Fe₂O_3(s) + 3C → 2Fe_(s) + 3CO_(g)

    MnO_2(s) + 2C_(s) → Mn_(s) + 2CO_(g)

Carbon monoxide is also used as reducing agent.

    Fe₂O_3(s) + 3CO_(g) → 2Fe_(s) + 3CO_2(g)

Aluminium is used as reducing agent for the reduction of certain oxides of metals like chromium, manganese and iron. A large amount of heat is produced during the process and the metal is obtained in liquid (molten) state. The process is known as THERMIT PROCESS.

    Cr₂O_3(s) + 2Al_(s) → 2Cr_(l) +Al₂O_3(s)

    3MnO_2(s) + 4Al_(s) → 3Mn_(l) + 2Al₂O_3(s)

    Fe₂O_3(s) + 2Al_(s) → 2Fe_(l) + Al₂O_3(s)

Chemical reduction method cannot be used for highly reactive metals like sodium, potassium, aluminium, etc. Oxides of such metals are reduced by electrolytic reduction method.

Explain Electrochemical Reduction giving example.

ANS : Oxides of highly reactive metals like sodium, potassium and aluminium cannot be reduced by using chemical reduction ( by carbon or aluminium). If carbon is used large amount of heat is required and metal carbide is formed. These metals are obtained by electrolysis of their fused (molten) salts. The cathode acts as the reducing agent as it supplies electrons to metal ions.

ELECTROLYSIS OF SODIUM CHLORIDE
    In this process molten sodium chloride is taken as electrolyte in an electrolytic cell. The reactions taking place at the two electrodes are :
NaCl_(l) → Na⁺ + Cl^-

Na⁺ + e^- → Na_(s)
(at cathode)

Cl^- → Cl + e^-
(at anode)

Cl + Cl → Cl_2(g)

    If aqueous solution of sodium chloride is taken instead of molten sodium chloride, reduction of hydrogen ions (2H⁺) to hydrogen (H₂ gas) takes place instead of reduction of sodium ion(Na⁺) to sodium metal.

Explain : Reactivity Series of Metals.

ANS : The series of metals in the decreasing order of their reactivities is called reactivity series of metals. Some metals like sodium and potassium are highly reactive whereas metals like copper, silver and gold have very low reactivity.

The reactivities of metals can be compared by their reaction with dilute acid or by comparing their oxidation potential with the standard hydrogen potential. Based on their reaction with dilute acids the following series has been prepared :

K > Na > Ca > Mg > Al > Zn > Fe > Pb > (H) > Cu > Hg > Ag > Au

The metals on the left of the hydrogen in the series are more reactive and they can displace hydrogen from acids. Metals on the right side of hydrogen are less reactive and they cannot liberate hydrogen from dilute aqueous acids.

similarly, a more reactive metal can displace a less reactive metal from its solution. Thus, a strip of more reactive zinc displaces less reactive copper from aqueous copper sulphate solution (Displacement reaction). The blue colour of copper sulphate solution disappears gradually and brown granules of copper are seen at the bottom.

Zn_(s) + CuSO_4(aq) → ZnSO_4(aq) + Cu_(s)

If a strip of copper is placed in the solution of ZnSO₄, no chemical reaction occurs as copper is less reactive than zinc.

Write two equations each for obtaining metal oxides and hydroxides.

ANS :
OXIDES

When sodium reacts with oxygen it forms sodium oxide.
4Na_(s) + O_2(g) → 2Na₂O_(s)

Iron reacts with steam and forms iron oxide and hydrogen gas.
3Fe_(s) + 4H₂O_(g) → Fe₃O_4(s) + 4H_2(g)

HYDROXIDES

Sodium oxide reacts with water and forms sodium hydroxide.
Na₂O_(s) + H₂O_(l) → 2NaOH_(aq)

Magnesium reacts slowly with cold water and forms magnesium hydroxide and hydrogen gas.
Mg_(s) + 2H₂O_(l) → Mg(OH)_2(aq) + H_2(g)

Give names of different steps of metallurgy and write a brief note on each step.

ANS : Different steps involved in metallurgy are :

Crushing and grinding of ore
Concentration or enrichment of ore
Roasting, calcination and smelting
Reduction
Refining and purification of metals

CRUSHING AND GRINDING OF ORE : The ore in the form of big rocks is broken into small pieces with the help of crushers. These small pieces are then powdered with the help of a ball mill or stamp mill.

CONCENTRATION OR ENRICHMENT OF ORE : The process of removal of impurities from an ore is called ' Ore Concentration'. Different methods are employed for concentration of ore depending on the nature of ore and the impurities in it.

Froth Floatation Process is used for the concentration of sulphide ores.

Magnetic Separation method is used for removal impurities present in an ore with magnetic properties or for concentration of a nonmagnetic ore containing magnetic impurities.

Centrifugal method is used when there is a large difference in the densities of ore and impurities.

Ores of highly reactive metals are concentrated by chemical method.

ROASTING, CALCINATION,SMELTING :
Roasting is used to convert sulphide ores into oxides by heating for a longer period.

Calcination is the process of heating the ore strongly in absence of air to remove (i) volatile impurities (ii)water [from hydrated ore] or (iii) to convert carbonate ore into metal oxide.

Smelting is used to get an ore reduced to metal by heating whereby the metal is obtained in molten state.

REDUCTION : The conversion of metal oxide into metal is called 'Reduction'. For chemical reduction, reducing agents like carbon, carbon monoxide and aluminium are used. Metals like zinc, iron, copper, nickel, tin and lead are obtained by chemical reduction of their oxides.
Fe₂O_3(s) + 3C_(s) → 2Fe_(s) + 3CO_(g)

3MnO₂ + 4Al → 3Mn + 2Al₂O₃

The oxides of highly reactive metals cannot be reduced by chemical reduction using carbon or aluminium. Such metals are extracted by electrolytic reduction of their molten salts. During electrolysis the cathode acts as reducing agent by supplying electrons to metal ions. Sodium, potassium and aluminium are obtained by this method.

REFINING OF METALS : The metals obtained from their ores after several metallurgical processes still contain some impurities. The removal of these impurities is called refining of metals. Refining is done mainly by two processes.

LIQUATION (Liquefaction) method is used to remove impurities from metals like tin, lead and bismuth whose melting points are low as compared to those of impurities.
ELECTROLYTIC REFINING is used to refine metals like zinc, lead, aluminium, copper, silver, gold, etc. The impure metal works as anode, a strip of pure metal is taken as cathode and a suitable salt of the metal to be purified in aqueous solution is taken as an electrolyte. The impure metal enters the solution from anode and then gets deposited on cathode. The impurities remain in the solution.

In addition, the metals (in fact, metalloids) like silicon, germanium, etc. which are needed in ultrapure state for certain applications are obtained by zone refining method.

Write a note in detail : Refining of Metals by Electrochemical Method.

ANS : Metals like zinc, lead, aluminium, copper, silver, gold, etc. are refined by this process.

A rod of impure metal is taken as anode and a strip of pure metal is taken as cathode. an aqueous solution of a simple or complex salt of the metal to be purified is taken as electrolyte. On passing electric current at suitable voltage, pure metal is deposited at the cathode. The impurities either remain in the solution or collect at the bottom of the anode as 'Anode Mud'.

For example, to obtain pure copper, impure copper rod is taken as anode, a strip of pure copper is taken as cathode and aqueous solution of copper sulphate is taken as the electrolyte.

The reactions taking place at both the electrodes are :

Crude copper contains very small amounts of iron, silver and gold. Iron dissolves in the solution whereas silver and gold collect at anode as anode mud and are obtained in the native state.

Describe Extraction of aluminium from bauxite.

ANS :
CONCENTRATION OF BAUXITE [BAYER'S PROCESS] :

bauxite is concentrated by Bayer's process to obtain pure aluminium oxide (alumina).
Bauxite is first roasted by heating to convert ferrous oxide into ferric oxide. The ore is then dried, powdered and treated with 45% aqueous solution of caustic soda (sodium hydroxide) and is heated to about160°C in a closed vessel for 6 to 8 hours at 5 to 6 atmospheric pressure. Sodium aluminate is formed.

The insoluble impurities are filtered. Sodium aluminate is soluble in water and is obtained as filtrate. Sodium aluminate is then hydrolysed by adding excess water and constantly stirring it whereby gelatinous precipitates of aluminium hydroxide are obtained. To enhance the formation of Al(OH)₃, some Al(OH)₃ is added from outside as seedling.

The precipitates of Al(OH)₃ are then washed repeatedly with water, dried and heated up to 1200°C.

Thus, 99.5% pure alumina (Al₂O₃) is obtained.

ELECTROLYSIS OF ALUMINIUM OXIDE [HALL-HAROULT PROCESS] :

A special electrolytic cell invented by 'Hall' and 'Haroult' is used to reduce alumina to aluminium metal.

Pure aluminium oxide is mixed with cryolite (Na₃AlF₆). The mixture is then melted in iron tank lined with carbon from inside. The carbon lining acts as cathode. The anode consists of a number of carbon rods which are dipped into the molten mass of Al₂O₃ and cryolite.

When electric current is passed, aluminium metal is obtained at the cathode and oxygen gas gets liberated at anode. This oxygen gas reacts with carbon anode to form carbon dioxide. Due to this the carbon anode is gradually consumed.

Molten aluminium metal being heavier than the electrolyte, is collected at the bottom of the tank.
At Cathode

2Al⁺³_(aq) + 6e^- → 2Al_(l)

At Anode

C_(s) + O^-2 → CO_(g) + 2e^-

C_(s) + 2O^-2 → CO_2(g) + 4e^-

Describe extraction of iron using Blast Furnace.

ANS : Blast furnace is used to obtain iron metal from haematite (Fe₂O₃). A proper mixture of haematite, coke and calcium carbonate is added to the blast furnace from the top and hot air is blown from the bottom of the blast furnace.

[Diagram of blast furnace is only for information]

At the bottom of the furnace coke burns in air to form carbon dioxide and large amount of heat is produced.
C_(s) + O_2(g) → CO_2(g) + Heat

In the center of the furnace carbon dioxide reacts with hot coke and forms carbon monoxide.
CO_2(g) + C_(s) → 2CO_(g)

In the upper part of the furnace the temperature is 400°C to 700°C. Here the reaction between iron oxide and carbon monoxide takes place in three stages and iron oxide is reduced to iron.
3Fe₂O_3(s) + CO_(g) → 2Fe₃O_4(s) + CO_2(g)

Fe₃O_4(s) + CO_(g) → 3FeO_(s) + CO_2(g)

FeO_(s) + CO_(g) → Fe_(s) + CO_2(g)

Due to large amount of heat produced in the furnace, limestone (CaCO₃) decomposes to calcium oxide. Calcium oxide reacts with sand (SiO₂) present as impurity in the ore and forms calcium silicate known as SLAG.
CaO_(s) + SiO_2(s) → CaSiO_3(l)[slag]

Both slag and iron ore are in molten state due to very high temperature in the lower part of the furnace. Both are collected separately from the bottom of the furnace. Once started, the blast furnace works for many months.

Mention physical properties of metals.

ANS :

Metals have lustrous surface which can be polished.
Metals are solid (exception : gallium and mercury are in liquid state).
Metals are heavy (exception : sodium, potassium, magnesium and aluminium are comparatively lighter).
Metals are hard and cannot be cut with knife (exception : sodium, potassium and lead are soft and can be cut with knife).
Metals are good conductors of heat and electricity (exception : lead and mercury are bad conductors of heat).
Metals are ductile, i.e., they can be drawn in to wires.
Metals are malleable, i.e., they can be hammered and sheets can be prepared from them.
Metals have high melting points and boiling points. The melting point of iron is 1539°C.
Metals possess high tensile strength.
Most of the metals are sonorous, i.e., they produce sounding noise on collision.
Metals can be mixed with other metals and nonmetals to form alloys.

Write a note on chemical properties of metals OR Explain how metals react with oxygen, water, dilute acids, chlorine and hydrogen giving examples.

ANS : Metals are electropositive elements since they have a tendency to lose electrons and form positively charged ions.

REACTION WITH OXYGEN : Metals form oxides with oxygen. These oxides are basic in nature because when dissolved in water they form alkaline solutions. For example, sodium reacts with oxygen to give sodium oxide.
4Na_(s) + O_2(g) → 2Na₂O_(s)

Sodium oxide reacts with water to form sodium hydroxide ( an alkali).
Na₂O_(s) + H₂O_(l) → 2NaOH_(aq)

Oxides of metals like aluminium and zinc are called AMPHOTERIC OXIDES as they exhibit both acidic and basic behaviour.

REACTION WITH WATER : Metals form either metal oxides or hydroxides when they react with water. Hydrogen gas is evolved in both cases.
Highly reactive metals like sodium and potassium react violently with cold water.
2Na_(s) + 2H₂O_(l) → 2NaOH_(aq) + H_2(g)

Magnesium reacts slowly with cold water but rapidly with hot boiling water.
Mg_(s) + 2H₂O_(l) → Mg(OH)_2(aq) + H_2(g)

Zinc and iron react with steam only (i.e., they do not react with cold or warm water).
Zn_(s) + H₂O_(g) → ZnO_(s) + H_2(g)

3Fe_(s) + 4H₂O_(g) → Fe₃O_4(s) + 4H_2(g)

Less reactive metals like lead, copper, silver and gold do not react with water at all.

REACTION WITH DILUTE ACIDS : Depending on their reactivity, metals react with dilute acids at different rates and liberate hydrogen gas.
Mg_(s) + 2HCl_(aq) → MgCl_2(aq) + H_2(g)

2Al_(s) + 6HCl_(aq) → 2AlCl_3(aq) + 3H_2(g)

Copper does not react with dilute acids.

REACTION WITH CHLORINE : Metals react with chlorine to form metal chlorides which are ionic compounds.
2Na_(s) + Cl_2(g) → 2NaCl_(s)

REACTION WITH HYDROGEN : All metals do not combine with hydrogen. Only reactive metals like sodium, potassium and calcium form their hydrides with hydrogen.
2Na_(s) + H_2(g) → 2NaH_(s)

Ca_(s) + H_2(g) → CaH_2(s)

2K_(s) + H_2(g) → 2KH_(s)

Write a note on Corrosion.

ANS :

Corrosion is a process in which rust is formed on metal surface when it is exposed to air, water or moisture. Oxygen of air, carbon dioxide and moisture(water) are mainly responsible for corrosion.
Some of the metals undergo corrosion. For example : (i) Green coloured salt is formed on copper and brass vessels.
(ii) Iron becomes rusted because of its reaction with oxygen of air. Iron rust is mainly iron oxide (Fe₂O₃.xH₂O) which is red in colour.
Corrosion results in wastage of billions of rupees. Therefore, it is better to prevent corrosion.

PREVENTION OF CORROSION :

Rusting of iron can be prevented by covering its surface with a paint. This method is less effective because rusting starts again if the paint is removed from some part.
Iron is galvanised by applying a thin layer of more active zinc on its surface. Zinc prevents rusting effectively. Even if a small amount of zinc is removed from the surface, rusting does not start again because zinc spreads to cover the surface and prevents corrosion.
To prevent corrosion of iron plates of steamers, blocks of more reactive metals like magnesium or zinc are combined with iron plates and then allowed to come in contact with seawater. Here iron plates act as cathode and magnesium(or zinc) act as anode because the oxidation potential of iron is less. The magnesium/zinc blocks get corroded in seawater so they are replaced periodically.
Corrosion can also be prevented by using suitable chemical inhibitors which form a chemical bond with the metal surface and prevent corrosion.
A layer of enamel applied on the metal can prevent corrosion.

Write a note on Alloys.

ANS : An alloy is a homogeneous solid solution of two or more metals or a metal and a nonmetal. An alloy is generally prepared by heating the mixture of its constituents to molten state and then cooling it at room temperature. An alloy is prepared to obtain material with desired properties because the properties of constituents of an alloy are modified to some extent. Sometimes the melting point of an alloy is lower than that of the constituents. For example, solder is an alloy of lead and tin. Its melting point is lower than that of lead and tin and it is used in soldering of electrical wires. [Table to be posted]

Pure gold cannot be used to make jewellery as it is very soft. To make it hard, it is generally alloyed with copper or silver. The purity of gold is expressed in CARATS. Pure gold is 24 carats. 18 carat gold means it contains 18 parts of gold in 24 parts by weight of the alloy.

Distinguish between metals and nonmetals based on physical properties.
ANS :

Distinguish between metal and nonmetal based on chemical properties.

ANS:

METALS - II : BRIEF ANSWERS

2007-03-22T01:31:00.000-07:00

ANSWER IN BRIEF

*INDEX-TOPIC SEARCH

Explain : 'Earth - A treasure of Elements'.

ANS:

Elements necessary for life are available in the form of minerals [native state or compound form] from all three main spheres of earth.
LITHOSPHERE consists of rocks and sand. It provides elements like aluminium, sodium, iron, calcium, copper, etc. in the form of their oxides and sulphides.
HYDROSPHERE consists of all water sources like seas, rivers, lakes, etc. It supplies elements like chlorine, bromine, sodium, potassium, magnesium, etc. in the form of their compounds.
ATMOSPHERE is the envelope of gases surrounding the earth. It provides nitrogen, oxygen, carbon dioxide, etc.

Hence the earth is a treasure of elements for us.

Explain : Roasting giving examples.

ANS: Roasting is a process in which the concentrated ore is heated for a longer period. This process is used to convert sulphide ore into oxide by removing sulphur. The volatile impurities are removed by roasting.

Describe the importance of Ultrapure metals.

ANS: Modern science and technology require ultrapure elements for several specific applications. Elements like silicon, boron and germanium used as semiconductors, in space and in technology must be ultrapure. Elements like uranium used in nuclear field must also be ultrapure. Amount of boron in uranium is 1 ppm. Neutron produced during nuclear fission breaks boron atom and the chain reaction stops. A similar problem arises when germanium is used as semiconductor because it contains 1 ppm of copper. Such ultrapure elements are obtained by zone refining method or 'van Arkel' method.

Write in brief about the Fractional Refining Process (Zone Refining Process).

ANS: The fractional refining process [zone refining process] is used to obtain ultrapure elements [metals with almost 100% purity] used in some specific applications like semiconductors, space technology, nuclear energy, etc. During the process impurities are removed on the basis of fractional crystallization. The impurities being more volatile remain in solution in molten state and their solubility decreases as the molten metal cools and can be separated in the form of crystals. This gives ultrapure element. Silicon, boron, germanium, etc.are obtained in ultrapure form by this method and are used in semiconductor technology.

Give the names of different steps of metallurgy.

ANS: Different steps involved in metallurgy are :

Crushing and grinding of ore
Concentration or enrichment of ore
Roasting, calcination and smelting
Reduction
Refining and purification of metals

Distinguish between roasting and calcination.

ANS: