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

GIVE ANSWER IN DETAIL

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1. 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.
       
     
     
   
   
   
2. 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.
     
   
   
   
3. 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.
     
   
   
   
4. 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.
         
       
       
     
     
   
   
   
5. 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.
     
   
   
   
6. 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.
     
   
   
   
7. 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.
     
   
   
   
8. 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.
     
   
   
   
9. 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.
     
   
   
   
10. 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.
      
    
    
    
11. 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.
      
    
    
    
12. 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.
      
    
    
    
13. 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

ANSWER IN BRIEF

*INDEX-TOPIC SEARCH

1. 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.
     

   
   

   
   
2. 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.
     

   
   

   
   
3. 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.
     

   
   

   
   
4. 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].
   

   
   
5. Distinguish between xylem and phloem.
   
   ANS:
   
   
6. Distinguish between blood and lymph.
   
   ANS :
   
   
7. Distinguish between artery and vein.
   
   ANS :
   
   

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

*INDEX-TOPIC SEARCH

MULTIPLE-CHOICE QUESTIONS

SELECT THE CORRECT ALTERNATIVE:

1. ______ is associated with the transport of water in plants.
   
   
   
   1. Xylem
   2. Phloem
   3. Chloroplast
   4. Aerenchyma
      
   
   
2. Tracheae are found in ______ plants.
   
   
   
   1. pteridophytes
   2. gymnosperms
   3. angiosperms
   4. all three
      
   
   
3. The inner wall of the tracheids and tracheae shows deposition of ______.
   
   
   
   1. starch
   2. glucose
   3. lignin
   4. protein
      
   
   
4. Which of the following is not a property of blood plasma ?
   
   
   
   1. It is pale yellow
   2. It is nonliving
   3. It is acidic
   4. It contains hormones
      
   
   
5. Which of the following is not a blood corpuscle ?
   
   
   
   1. Leucocyte
   2. Erythrocyte
   3. Thrombocyte
   4. Nymphocyte
      
   
   
6. Which of the following is true for human erythrocytes ?
   
   
   
   1. They are biconvex.
   2. They have nucleus.
   3. They contain haemoglobin.
   4. They do not have nucleus but possess mitochondria.
      
   
   
7. ______ is a respiratory pigment.
   
   
   
   1. Haemoglobin
   2. Chlorophyll
   3. Mesophyll
   4. Adrinalin
      
   
   
8. The lifespan of erythrocytes is about ______ days.
   
   
   
   1. 100
   2. 120
   3. 140
   4. 180
      
   
   
9. Which of the following is false ?
   
   
   
   1. Erythrocytes are light red in colour.
   2. Haemoglobin is a respiratory pigment.
   3. Lymphocytes produce immunoglobulins.
   4. Thrombocytes destroy pathogens.
      
   
   
10. ______ is a necessary mineral for clotting of blood.
    
    
    
    1. Calcium
    2. Potassium
    3. Iron
    4. Zinc
       
    
    
11. ______ converts liquid fibrinogen into solid fibres of fibrin.
    
    
    
    1. Thromboplastin
    2. Oxyhaemoglobin
    3. Immunoproteins
    4. Thrombin
       
    
    
12. There are ______ types of antigens on the erythrocytes.
    
    
    
    1. two
    2. three
    3. four
    4. five
       
    
    
13. The blood group of a person is O and Rh (-ve). He can donate blood to...
    
    
    
    1. any person
    2. a person with group O
    3. A person with Rh (-ve)
    4. none
       
    
    
14. Which of the following is true ?
    
    
    
    1. Heart purifies blood.
    2. Heart separates excretory products from blood.
    3. Heart circulates blood.
    4. Blood flows from heart to lungs.
       
    
    
15. The relaxed state of yeart is called ______.
    
    
    
    1. Diastolic state
    2. Systolic state
    3. Thermostatic state
    4. Primary state.
       
    
    
16. The structure for excretion and osmoregulation in sponges is ______.
    
    
    
    1. osculum
    2. contractile vacuole
    3. nephridia
    4. flame cell
       
    
    
17. Urine mainly consists of ______.
    
    
    
    1. Uranium
    2. Urea
    3. CO₂
    4. sugar
       
    
    
18. Birds excrete wastes in the form of ______.
    
    
    
    1. urea
    2. proteins
    3. uric acid
    4. water
       
    
    
19. Which structure is responsible for transportation of water in pteridophytes ?
    
    
    
    1. Tracheids
    2. Tracheae
    3. Sieve cells
    4. Sieve tubes
       
    
    
20. Which structure has lignified cell wall ?
    
    
    
    1. Sieve tube
    2. Tracheids
    3. Trachea
    4. Sieve cells
       
    
    
21. Which blood cells contain haemoglobin ?
    
    
    
    1. RBC
    2. WBC
    3. Platelets
    4. Lymphocytes
       
    
    
22. Which blood cells produce immunoglobin ?
    
    
    
    1. Platelets
    2. Erythrocytes
    3. Lymphocytes
    4. Leucocytes
       
    
    
23. Which chemical is released when blood cells rupture ?
    
    
    
    1. Prothrombin
    2. Fibrin
    3. Thrombin
    4. Thromboplastin
       
    
    
24. Where are antigens for blood group located ?
    
    
    
    1. WBC
    2. RBC
    3. Platelets
    4. Blood plasma
       
    
    
25. How many chambers are present in human heart ?
    
    
    
    1. 1
    2. 2
    3. 3
    4. 4
       
    
    
26. Where is bicuspid valve found in human heart ?
    
    
    
    1. Between two atria
    2. Between left auricle and left ventricle
    3. Between two ventricles
    4. Between right auricle and right ventricle.
       
    
    
27. Through which parts of the heart does oxygenated blood flow ?
    
    
    
    1. Both atria
    2. Left auricle and left ventricle
    3. Both ventricles
    4. Right auricle and right ventricle
       
    
    
28. Where does deoxygenated blood get oxygenated ?
    
    
    
    1. Atrium
    2. Heart
    3. Lungs
    4. Kidneys
       
    
    
29. Which type of blood flows through all arteries ?
    
    
    
    1. Impure
    2. Pure
    3. Toxic
    4. With nitrogenous waste
       
    
    
30. What is the shape of human heart ?
    
    
    
    1. Round
    2. Bean shaped
    3. Conical
    4. Triangular
       
    
    
31. Carboxy-haemoglobin is formed when haemoglobin reacts with...
    
    
    
    1. CO
    2. CO₂
    3. O₂
    4. CH₄
       
    
    

SHORT QUESTIONS

ANSWER IN SHORT:

1. 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.
   
   
2. 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.
   
   
3. What are tracheids ?
   
        ANS : Tracheids are long, thin and spindle shaped cells of xylem of a plant.
   
   
4. Why are tracheids dead cells ?
   
        ANS : Tracheids are dead cells because their nuclei are disintegrated.
   
   
5. 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.
   
   
6. 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.
   
   
7. 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.
   
   
8. Where are plant hormones synthesized ?
   
        ANS : Plant hormones are synthesized at the shoot and root tips.
   
   
9. 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.
   
   
10. 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.
    
    
11. 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.
    
    
12. 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.
    
    
13. Define : Sieve pores.
    
         ANS : The perforations in the transverse walls (sieve plates) present between sieve tube cells are called sieve pores.
    
    
14. Define : Translocation.
    
         ANS : The transport of food from leaves to other parts of plants is called translocation.
    
    
15. 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.
    
    
16. 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.
    
    
17. Mention two main components of blood.
    
         ANS : Blood plasma and blood corpuscles are the two main components of blood.
    
    
18. Mention three main types of blood corpuscles.
    
         ANS : Erythrocytes (RBC), leucocytes (WBC) and thrombocytes (platelets) are three types of blood corpuscles.
    
    
19. Why is haemoglobin called respiratory pigment ?
    
         ANS : Haemoglobin is called respiratory pigment because it transports respiratory gases (O₂ and CO₂) between lungs and organs.
    
    
20. Where are erythrocytes formed ?
    
         ANS : Erythrocytes are formed in the bone marrow.
    
    
21. Which type of WBC produce immunoglobulins ?
    
         ANS : Lymphocytes produce immunoglobulins.
    
    
22. What is serum ?
    
         ANS : Serum is a viscous pale yellow liquid that oozes out from the periphery of a blood clot.
    
    
23. Define : Blood transfusion.
    
         ANS : The transfer of blood from a healthy donor to a needy patient is called blood transfusion.
    
    
24. 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.
    
    
25. Mention different blood groups in human beings.
    
         ANS : The blood groups present in human being are : A, B, AB and O.
    
    
26. 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.
    
    
27. 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.
    
    
28. Define : Artery.
    
         ANS : The blood vessel which carries blood from heart to different organs of the body is called artery.
    
    
29. Define : Vein.
    
         ANS : The blood vessel which carries blood from different organs to the heart is called vein.
    
    
30. 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.
    
    
31. Which cells does lymph contain ?
    
         ANS : Lymph contains lymphocytes.
    
    
32. What constitutes lymphatic system ?
    
         ANS : Lymphatic system consists of lymphatic vessels, lymphatic capillaries, lymph nodes and lymph glands.
    
    
33. Define : Excretion.
    
         ANS : The biological process involved in the removal of liquid excretory substances from the body is called excretion.
    
    
34. Define : Osmoregulation.
    
         ANS : The process of maintaining the required amount of water and proper ionic balance in the body is called osmoregulation.
    
    
35. 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.
    
    
36. What is the structure for excretion in earthworm known as ?
    
         ANS : The structure for excretion in earthworm is known as nephridia.
    
    
37. What is the structure for excretion in platyhelminthes known as ?
    
         ANS : The structure for excretion in platyhelminthes is known as flame cells.
    
    
38. What does hydra have for excretion and osmoregulation ?
    
         ANS : Hydra has oral opening for excretion and osmoregulation.
    
    
39. Mention the types of nephridia in earthworm.
    
         ANS : The types of nephridia in earthworm are : (i) septal (ii) pharyngeal and (iii) integumentary.
    
    
40. 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.
    
    
41. What is enteronephric excretion ?
    
         ANS : In enteronephric excretion the excretory products are poured into the alimentary canal through nephridia.
    
    
42. What is exonephric excretion ?
    
         ANS : In exonephric excretion the excretory products are thrown out of the body through the skin.
    
    
43. Where are human kidneys located ?
    
         ANS : Human kidneys are located in the abdomen on the dorsal side.
    
    
44. What is ultrafiltration ?
    
         ANS : The filtration of blood carrying waste material under pressure in glomerulus is known as ultrafiltration.
    
    
45. 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.
    
    
46. Which substance provides mechanical support to the walls of xylem ?
    
         ANS : Lignin provides mechanical support to the walls of xylem.
    
    
47. What is transported through sieve plate ?
    
         ANS : Food is transported through sieve plate.
    
    
48. Mention the colour of blood and lymph.
    
         ANS : The colour of blood and lymph is red and pale yellow respectively.
    
    
49. What is the shape of human erythrocytes ?
    
         ANS : Human erythrocytes are round, biconcave in shape.
    
    
50. Which mineral is present on haemoglobin ?
    
         ANS : Iron is present in haemoglobin.
    
    
51. Where are blood cells produced in our body ?
    
         ANS : Blood cells are produced in the bone marrow of long bones.
    
    
52. Mention two functions of WBC.
    
         ANS : The two functions of WBC are : (i) They destroy pathogenic microorganisms. (ii) They destroy harmful substances.
    
    
53. Give examples of enucleated blood cells.
    
         ANS : RBC (erythrocytes) and platelets are enucleated blood cells.
    
    
54. 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.
    
    
55. Where is thromboplastin produced ?
    
         ANS : Thromboplastin is produced at the point of injury where blood vessels rupture.
    
    
56. Which mineral is needed to convert prothrombin into thrombin ?
    
         ANS : Mineral calcium is needed to convert prothrombin into thrombin.
    
    
57. What converts fibrinogen to fibrin ?
    
         ANS : Thrombin converts fibrinogen to fibrin.
    
    
58. Where are blood antigens located ?
    
         ANS : Blood antigens are located on the surface of erythrocytes.
    
    
59. 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.
    
    
60. 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.
    
    
61. 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.
    
    
62. Where is tricuspid valve present in human heart ?
    
         ANS : Tricuspid valve is present between right atrium and right ventricle of heart.
    
    
63. To which part of the body does pulmonary artery supply blood ?
    
         ANS : Pulmonary artery supplies blood to lungs (from heart).
    
    
64. What is the function of pulmonary vein ?
    
         ANS : Pulmonary vein collects blood from lungs and supplies it to the left atrium.
    
    
65. Define : Conduction.
    
         ANS : The upward movement of water (absorbed by roots) through tracheids is called conduction.
    
    
66. 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.
    
    
67. What are blood capillaries ?
    
         ANS : Fine, thin-walled and narrow tubular branches of arterioles which reunite to form venules are called blood capillaries.
    
    
68. Define : Companion cell.
    
         ANS : The cells arranged laterally and longitudinally to sieve tube cells in the phloem of angiospermic plants are called companion cells.
    
    
69. Which organelle is absent in human RBC ?
    
         ANS : Nucleus and mitochondria are absent in RBC.
    
    
70. 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.