FORM 2 END OF TERM 3 2022 Exam-BIOLOGY Answers




END OF TERM 3- 2022



  1. The diagram below represents a transverse.                                                                          

Section of a young stem.


  1. Name the parts labeled A and B                                                                            (2mks)

A         Epidemis

 B        Pith

  • State functions of the part labeled C, D, E.                                                            (3mks)
  • E. Translocate manufactured food
  • D. Dendes to give rise to new cells that produce secondary system and phloem
  • E. Transports water mineral salts from the roots to the leaves
  • a) Why are people with blood group 0 are universal donors.                                    (2mks)
  • Because they donate blood to all other blood groups

b)   A person with blood group AB requires blood transfusion. Name blood groups of

      the donor.                                                                                                                    (2mks)

  • A,AB,B,O
  • a) The type of circulatory system found in members of the class inseda is               (1mk)                          
  • Open circulatory system

b) Name the blood vessel that transports blood from

  1. Small intestine to the liver.                                                                            (1mk)
  2. Hepatic portal vein
  3. Longs to the heart.                                                                                         (1mk)
  4. Pulmonary vein

c)  In what form is oxygen transported from the longs to the body tissues?                    (1mk)

  • Oxyhaemoglobin
  • Distinguish between natural and acquired immunity.                                                                 (2mks)
  • Natural immunity – transmitted from parent to offspring e.g after suffering from a disease.
  • State four functions of blood other than transport.                                                           (4mk)
  • regulation of body temperature
  • regulation of PH of body fluids
  • Defence against diseases – causing organism
  • Prevent excessive bleeding by enhancing clotting
  • Name the antigens that determine human blood groups.                                                 (2mks)
  • antigen  A
  • Antigen  B
  • State structural differences between arteries and veins.                                                 (6mks)
thick muscular wallsthin less muscular walls
No valvesHave valves
Narrow lumenWide lumen
  • Give reasons for carrying out the following procedure when making temporary slides.                              
  • Making thin sections.                                                                                              (1mk)
  • To reduce layers of cell and allow light to pass through
  • Adding water to the plant.                                                                                       (1mk)
  • to make cells turgid
  • Placing coverslip over the plant section.                                                                 (1mk)
  • to hold specimen in position n ; to protect objectic lens exclude air, dust, foreign particles.
  • a) Distinguish between diffusion and osmosis.                                                                 (2mks)
  • diffusion is the movement of molecdes from a region of high concentration to a region of low concentration                                                                              (2mks)

b) The diagram below show a red blood cell that was subjected to certain treatment.


Account for the shape of the cell.                                                                                     (2mks)

  • The red blood cell was placed in hypertonic solution. It loose water by osmosi and become crenated.
  • a) Name the material that strengthens xylem vessels.                                                        (1mk)
  • Lignin

            b) Name the tissue that is removed when the bark of the dicotyledonous is ringed.         (1mk)

  • Phloem

11.  a) State what happens during light stage of photosynthesis.                                       (4mks)

  • Light stage is light dependent. it take place in the grand of the chloroplast
  • Light trapped is used to split water molecules into hydrogen and oxygen ions through photolysis energy is formed and it is stored in the form of ATP

      b). What are the end products light stage.                                                                   (2mks)

  • Hydroge ions; oxygen gas; ATP

12. State 2 factors affecting enzymatic activities.                                                                 (4mks

  • Temperature – increase in temperature increase enzymatic up to an optimum low temperature inactive enzymes high temperature denature enzymes.
  • Enzymatic activity as there is more active site

13. How does the following affect the rate of diffusion:                                                                                        

  • Diffusion   gradient.                                                                                              (2 mk)
  • The higher the concentration gradient the higher the rate of diffusion
  • Size of the molecules                                                                                            (2 mk)
  • Small size molecules diffuse faster than large and heavy molecules
  • Thickness of the membraine.                                                                               (2 mk)
  • The thicker the membrane the lower the rate of diffusion
  • this is because the distance covered by diffusing molecules is greater however if the membrane is thinner
  • the rate of diffusion is higher.
  • Temperature                                                                                                          (2mks)
  • Increase in energy increases kinetic energy of the molecules and this causes them to move faster hence increases in temperature
  • Increases the rate of diffusion and vie-versa.
  • Surface area to volume ration.                                                                              (2mks)
  • The greater the surface area to volume ration the higher the rate of diffusion

14. Explain how the following factors determine the daily energy requirements          

  1. Age                                                                                                                 (2mks)
  2. Young people are actively growing hence they require more energy.
  1. Occupation                                                                                                      (2mks)
  2. manual workers require more energy equivalent to work done by sederitary workers
  3. Sex                                                                                                                  (2mks)
  4. Men are more muscular hence require more energy than female to maintain every cell

15. Name the appropriate food substances for each of the following enzymes.

  1. Ptyalin.                                                                                                            (1mks)
  2. Starch
  3. Pepsin.                                                                                                             (1mks)
  4. Protein

b). State the two roles of mucus in the stomach.                                                        (2mks)

  • Forms protective partner to the stomach all against corrosions by hydrochloric acid and digestive enzymes

16. a) State 3 adaption of xylem to its function.                                                                    (3mks)

  • Walls are strengthen by deposition of ligning to ensure they don’t collapse
  • Hollow and narrow to aid caplilarity
  • Made up of dead cells to ensure passage of water.

b) Describe how 4 environment factors affect the rate of transportation.                              (8mks)

  • TEMPARATURE: The increase in internal temperature of the leaf which in turns increases latent heat of vaporization enhancing evaporation.
  • WIND; Wind carries away water vapour as fast as it diffuses out of the leaves increases the rate of transpiration.
  • HIGH LIGHT INTENSITY: Light intensity increases rate of photosynthesis where sugar is formed, which is osmotically vapour diffuses out at a higher rate thereby increasing rate of transpiration
  • LOW HUMIDITY: When atmosphere is dry or in low water vapour diffuses out of the leaves into dry atmosphere. Due to high saturated deficit water diffuses faster hence increased rate of transpiration.

17.a)  State the difference between dosed and open circulatory system.                                 (2mk)

  • transport fluid is not confined to the blood vessesl but contains in the general body cavity.
  • The transport fluid called blood is conveyed in special tubes reffered to as blood vessels

b).State two ways in which the heart muscles are adapted.                                                   (2mks)

  • are abel to initiate their own contraction
  •  presence of intercalated discs hence they do not get fatigue

18. State the role of the following organelles.                                                                        (6mks)

  1. Golgi apparatus
  2. They package and transport
  3. Ribosomes
  4. Site for protein synthesis
  5. Lysosomes
  6. They contain lytic enzymes that destroy aged and unwanted cells
  7. Mitochondrion
  8. Site for respiration
  9. Chloroplasts
  10. Site for photo synthesis
  11. Centrioles
  12. They form clia and flagella.