NUTRITION AND RESPIRATION IN ORGANISMS - III : LONG ANSWERS

GIVE ANSWER IN DETAIL

*INDEX-TOPIC SEARCH

1. 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.
     
   
   
   
2. 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.
   
   
3. 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.
   
   
4. 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.
   
   
5. 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.
   
   
6. 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.
   
   
7. 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.
     
   
   
   
8. 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.]
   
   
9. 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.
   
   
10. Distinguish between autotrophic nutrition and heterotrophic nutrition.
    
    ANS :
    
    
    
11. Distinguish between photosynthesis and respiration.
    
    ANS: