Biology Questions and Answers - Form 2 End Term 1 Exams 2022

QUESTIONS

1. Explain the following terms:
   1. Taxonomy (1mk)
   2. Species (1mk)
2. State the function of the following organelles
   • Lysosomes(1mk)
   • Golgi apparatus (1mk)
3. Name the form in which carbohydrates are stored in
   • Plant tissues
   • Animal tissues (2mks)
4. Name three photosynthetic cells in plants (2mks)
5. State three structural differences between arteries and veins(3mrk)
6. Give two reasons why clotting of blood is important (2mks)
7. Name one enzyme and one metal ion that are required in the blood clotting process 2mks)
8. The following diagram of a leaf shows what happens in a pant leaf during photosynthesis: -
   
   
   1. Give two ways in which leaves are adapted to absorb light(2mrks)
   2. Name the gases labelled X and Y(2mrks)
   3. Name the tissue that transports water into the leaf and sugars out of the leaf (2mrks)
   4. Explain why it’s an advantage for the plant to store carbohydrates as starch rather than as sugars(2mrks)
9. The diagram below represents a cell organelle
   
   
   1. Name the part labelled Y (1mrk)
   2. State the function of the part labelled X (1mrk)
10. State the role of emulsification in the digestion of fats in the alimentary canal (1mrk)
11. What is the function of hydrochloric acid in the alimentary canal? (2MRKS)
12. What is meant by the term gaseous exchange (1mrks.
13. Name and explain the characteristics of gaseous exchange surfaces. (4mrks)
14. State three ways in which leaves of plants are adapted to gaseous exchange(3mrks)
15. Explain stomatal distribution in plants of different habitats (6 mks)
16. The diagram below represents a transverse section of a young stem.
    
    
    1. Name the parts labelled A, B and D (3mrks)
    2. State the functions of the parts labelled C and E (2mrks)
    3. List three differences between the section above and the one that would be obtained from roots of the same plant. (3mrks)
17. Distinguish between guttation and transpiration (2mrks)
18. Other than transport, state one other function of xylem tissue in plants (1mrk)
19. Identify the part of the heart that initiates the heart beat (1mrk)
20. Give a reason why the left ventricle muscles are thicker than the right ventricles muscles (2mrks)
21. State the forms in which carbon (IV) oxide is transported in the blood
22. Explain how the following adaptation reduce transpiration in xerophytes
    1. Sunken stomata (2mrks)
    2. Thick waxy cuticle (1mrk)
23. Name the:
    1. Material that strengthens xylem tissue (1mrk);
    2. Tissue that is removed when the bark of a dicotyledonous plant is ringed (1mrk)
24. Why is it dangerous to sleep in an enclosed room with a burning jiko(3mrks)?
25. Why do plants not take in oxygen during the day although they need it for respiration (2mrks)
26. Draw and label the structure of a gill. (5mrks)

MARKING SCHEME

1. Explain the following terms:
   1. Taxonomy (1mk)
      study of classification
   2. Species (1mk)
      lowest unit in classification whose members can freely interbreed giving rise to viable offspring.
2. State the function of the following organelles
   • Lysosomes(1mk)
     Contains lytic enzymes which breakdown worn-out tissues and organelles
   • Golgi apparatus (1mk)
     site for synthesis of lysosomes
3. Name the form in which carbohydrates are stored in
   • Plant tissues - starch
   • Animal tissues - glycogen (2mks)
4. Name three photosynthetic cells in plants (2mks)
   Stomata
   Guard cells
   Palisade mesophyll cells
5. State three structural differences between arteries and veins(3mrk)
   

   Arteries	veins
   Narrow rumen Thick elastic muscles No valve except at the base of aorta and pulmonary artery	Wide rumen thin elastic walls Have valves

6. Give two reasons why clotting of blood is important (2mks)
   prevents excessive blood loss and, dehydration
   Prevents entry of pathogens
7. Name one enzyme and one metal ion that are required in the blood clotting process 2mks)
   Thromboplastin. Calcium ions
8. The following diagram of a leaf shows what happens in a pant leaf during photosynthesis: -
   
   
   1. Give two ways in which leaves are adapted to absorb light(2mrks)
      Broad and flat to absorb maximum light
      Have chloroplast with chlorophyll to trap light.
      Transparent cuticle to allow light to pass through
   2. Name the gases labelled X and Y(2mrks)
      X – Carbon (IV) Oxide
      Y – Oxygen
   3. Name the tissue that transports water into the leaf and sugars out of the leaf (2mrks)
      Xylem – Transports water
      Phloem – Sugars out of the leaf
   4. Explain why it’s an advantage for the plant to store carbohydrates as starch rather than as sugars(2mrks)
      Starch is insoluble in water, hence osmotically inactive; This reduces effect on absorption of water.
9. The diagram below represents a cell organelle
   
   
   1. Name the part labelled Y (1mrk)
      Intergrana;
   2. State the function of the part labelled X (1mrk)
      Site for photolysis; contains chlorophyll pigment absorbs light;
10. State the role of emulsification in the digestion of fats in the alimentary canal (1mrk)
    Increases surface area of fats for purpose of digestion;
11. What is the function of hydrochloric acid in the alimentary canal? (2MRKS)
    Accept any two correct
    Destroys any ingested pathogens;
    Provides acidic media for protein digesting enzymes (pepsin);
    Converts/ activates pepsinogen inactive form to pepsin;
12. What is meant by the term gaseous exchange (1mrks.
    Process by which the respiratory gases are passed across a respiratory surface.
13. Name and explain the characteristics of gaseous exchange surfaces. (4mrks)
    Moist to dissolve respiratory gases
    Has thin membrane to reduce distance covered by the respiratory gases for efficient diffusion
    Highly vascularized to create a steep concentration gradient facilitating diffusion
    Numerous to increase the surface area for gaseous exchange.
14. State three ways in which leaves of plants are adapted to gaseous exchange(3mrks)
    presence of stomata for faster gaseous exchange
    Intercellular spaces/air spaces in the leaf for movement/circulation of air
    film of moisture around the surface of cells for easy diffusion
    Broad/flattened shape to increase surface area
    Thin lamina to reduce distance of diffusion
    Exposed to air for easy diffusion
15. Explain stomatal distribution in plants of different habitats (6 mks)
    land plants have their stomata mainly on the lower side to reduce water loss but if on both sides then upper side has very few
    water plants, floaters, have stomata on upper side to enhance water loss in dry areas, plants have leaves with sunken stomata to reduce water loss by transpiration
    Plants in wet areas have stomata equally distributed on both sides.
16. The diagram below represents a transverse section of a young stem.
    
    
    1. Name the parts labelled A, B and D (3mrks)
       i. Epidermis
       ii. Pith
       iii. Vascular cambium.
    2. State the functions of the parts labelled C and E (2mrks)
       C- Transports manufactured food/ products of photosynthesis/ translocate food
       E- Transports water and mineral salts
    3. List three differences between the section above and the one that would be obtained from roots of the same plant. (3mrks)
       

       Section above	Section from root
       Xylem/ phloem form around cambium	Xylem star shaped and centrally placed
       Pith at the centre	No pitch
       Roof hairs absent	Roof hair present
       Epidermis has cuticle	Epidermis has no cuticle

17. Distinguish between guttation and transpiration (2mrks)
    Transpiration is the loss of water vapour through stomata, while guttation is loss or exudation of liquid water through hydathodes
18. Other than transport, state one other function of xylem tissue in plants (1mrk)
    support
19. Identify the part of the heart that initiates the heart beat (1mrk)
    Sinoatrio node/pace maker
20. Give a reason why the left ventricle muscles are thicker than the right ventricles muscles (2mrks)
    To generate high pressure to pump blood; to all parts of the body/ to furthest distance;
21. State the forms in which carbon (IV) oxide is transported in the blood
    Hydrogen carbonate (HCO₃)
    Carbonic acid;
22. Explain how the following adaptation reduce transpiration in xerophytes
    1. Sunken stomata (2mrks)
       Sunken stomata form pits; in which water vapour accumulates reducing rate of transpiration
    2. Thick waxy cuticle (1mrk)
       Water proof to reduce the rate of transpiration;
23. Name the:
    1. Material that strengthens xylem tissue (1mrk);
    2. Tissue that is removed when the bark of a dicotyledonous plant is ringed (1mrk)
24. Why is it dangerous to sleep in an enclosed room with a burning jiko(3mrks)?
    Burning charcoal produces carbon (II) Oxide which combines with haemoglobin to form carboxyhaemoglobin that is stable/ does not dissociate; reducing efficiency of haemoglobin in carrying oxygen leading to death; Rej death alone
25. Why do plants not take in oxygen during the day although they need it for respiration (2mrks)
    During the day there is presence of sunlight which provides energy for photolysis.
26. Draw and label the structure of a gill. (5mrks)
    

    Labelling 3mrks
    Drawing 2mrks, curved gill bar.