INSTRUCTIONS TO CANDIDATES

• Answer ALL the questions in this question paper.
• All answers must be written in the spaces provided after each question.
• Candidates should answer all the questions in English.

1. The graph below represents the growth pattern of animals in a certain phylum.
   
   
   1. Name the type of growth curve shown above.                                          (1 mark)
   2.  
      1. Identify the process represented by X.                                               (1 mark)
      2. Name the hormone responsible for the process in b(i) above. (1mark)
   3. State the importance of the growth of a pollen tube to a plant.                (1 mark)

2.  
   1. What is the function of Sodium hydrogen Carbonate that is added to test solution of non-reducing sugar.             (1 mark)
   2. The equation below represents a process X which is controlled by enzymes.
      
      
      • Name the process X and enzyme R
        Process X ………………………………………………………                 (1 mark)
        Enzyme R ……………………………………………………….                (1 mark)

3. The diagram shows an epidermal cell undergoing mitotic cell division.
   
   
   1. Name the stage of mitosis it represents     (1 mark)
   2. Name the structures
      A                           (1 mark)
      C                          (1 mark)

4. What is the effect of gibberellins on the shoots of plants?        (4 marks)                 

5.  
   1. Give two forms in which carbon (IV) oxide is transported in human blood. (2 marks)
   2. Name the enzyme that enhances the loading and off – loading of carbon (IV) oxide in the human blood.  (1 mark)

6.  
   1. What is the importance of the counter current flow in the exchange of gases in a fish?
   2. State two ways in which the tracheoles of an insect are adapted to their functions.  (2 marks)

7. The equation below represents a reaction that occurs during respiration in a cell.
   K + Phosphate →Adnenosine triphosphate
   1. Identify the compound K.            (1 mark)
   2. State two differences between K and ATP. (2 marks)        
   3. Name the organelle responsible for the production of energy in a cell muscle.    (1 mark)          

8. Explain how crops grown along roads can be a source of lead poisoning to human beings.  (2 marks)
9. Explain why plants growing in low altitude areas grow faster than those in high altitudes.(3 marks)

10. List down four phenotypic characteristics that have been selected for the production of strains suitable for modern agricultural purposes. (4 marks)
11. Name the type of eye defects that can be corrected by;
    1. Use of bifocal lens   (1 mark)
    2. Use of artificial lens  (1 mark)
    3. Use of concave lens    (1 mark)

12.  
    1. The length from the tail tip to the anus of a certain tilapia fish is 10 cm. The length from the tail tip to the mouth is 35cm. Calculate the tail power of the fish. (Show all your working).(2 marks)
    2. What is the significance of high tail power in fish? (1 mark)

13. List down three differences between the endocrine system and nervous system. (3 marks)
    

    Endocrine system	Nervous system
    i.  ii   iii	i.  ii  iii

14. Distinguish between the struggle for existence and survival for the fittest as used in the theory of natural selection. (2 marks)

15. The body temperatures of two animals A and B varied as below with environmental Temperature
    
    
    1. Which of the animals is;
       1. Endothermic …………………………………………………….. (1 mark)
       2. Ectothermic ……………………………………………………… (1 mark)
    2. With a reason, state which of the animals is likely to be widely distributed.(2 marks)

16. State three roles of oestrogen during the menstrual cycle (3 marks)

17. State three characteristics of cells at the zone of cell division in an apical meristem.
18. Below are diagrams of three leaves A, B and C. Construct a two step dichotomous key which can be used to identify each of them.   (4 marks)   
                  

19.  
    1. Name two mutagenic agents. (2 marks)
    2. Identify the type of gene mutations represented by the following pairs of words.
       1. Shirt instead of skirt    (1 mark)
       2. Hopping instead of shopping   (1 mark)
20. Liver damage leads to impaired digestion of fats. Explain this statement. (2 marks)
21. Explain why several lateral buds sprout when a terminal bud in a young tree is removed.(3 marks)

22.  
    1. State two structural adaptations that make xylem vessels suitable for transport of water and mineral salts.      (2 marks)
    2. List any three adaptations of the root hair cells to their functions                (3 marks)

23. Define the following terms:- (2 marks)
    1. Species
    2. Binomial nomenclature
24. What is the significance of active transport in the human body?                (3 marks)
25. Explain how the biceps and triceps muscles bring about the movement at the hinge joint of the elbow in man. (2 marks)

MARKING SCHEME

1.  
   1. Intermittent growth curve;
   2.  
      1. Growth;
      2. Ecdysone/ mounting hormone;
   3. Results in fertilization by conveying the male gametes to the female gamete;

2.  
   1. Neutralise excess acid (HCl);
   2. X – Condensation;
      R – Sucrase/ invertase;

3.  
   1. Anaphase
   2. A – Chromatids;
      C – Spindles;

4. Promote cell division/ cell elongation; initiates fruit formation without fertilization/ parthenocarpy; formation of side branches of stem; inhibits growth of adventitious roots; promotes dormancy in buds; Activates enzymes during germination; (4mks)

5.  
   1. – (Weak) carbonic acid ; acc bicarbonate ions/hydrogen carbonates
      - Carbamino haemoglobin;
   2. Carbonic anhydrase;     

6.  
   1. Maintains a steep concentration gradient across the respiratory surface; ensuring maximum extraction of oxygen from water to the blood; (2mks)
   2. Thin epithelium for faster/ quick diffusion of gases; Have tracheole fluid/ moist surface to dissolve gases in solution before diffusing; Highly branched to increase surface area for gaseous exchange; (mark first two)

7.  
   1. Adenosine Diphosphate/ ADP
   2. K – has two phosphate molecules
      ATP - has three phosphate molecules
      K – has less stored energy
      ATP – has more stored energy
   3. Mitochondrion rej; Mitochondria

8. Absorb lead from car exhaust fuses and pass it to animals and humans through the food chain.

9. Low altitude areas have favourable temperature for working of enzymes; faster metabolic process leading to faster growth; high concentration of Co₂ hence high rate of photosynthesis; High Co₂ concentration in low altitude leads to increased rate of respiration to generate energy for faster growth;
10.  
    • Resistance to diseases.
    • Early maturity
    • Adaptations to local conditions
    • High yields
    • Increased length of production

11.  
    1. Old sight/ presbyopia; (1mk)
    2. Cataract;    (1mk)
    3. Myopia/ short sightedness;   (1mk)

12.  
    1.  
       
    2. To create a high propulsive force/ thrust

13. Endocrine system Nervous system
    • Uses hormones to relay impulses     
    • Uses electrical charges caused by chemical concentration
    • Hormones transmitted through the         
    • Impulse transmitted through nerve cells; blood
    • Hormones reach all parts of the body     
    • Nerve impulses are transmitted through nerve cells to specific parts of the body;
    • Effects are long lasting                     
    • Effects are rapid and short lived;
    • Responses usually slow             
    • Responses usually fast;

14. Struggle for existence – environmental pressure on the population in order to survive; Survival for the fittest – advantageous variations an individual possesses to make it survive;

15.  
    1.  
       1. B 1
       2. A 1
    2. B1 – because it can keep its temperature constant despite variations in the environment 1

16.  
    • Stimulates repair and healing of endometrium 1
    • Stimulates production of LH 1
    • Stimulates development of female secondary sexual characteristics 1

17.  
    • Thin cell walls 1
    • Nerval cytoplasm 1
    • No vacuoles 1

18. 1a; Simple leaf……………………………. Go to 2 1
    1b; Compound leaf ……………………….. C 1
    2a; With parallel variation…………………. B 1
    2b; With network variation………………… A 1
    Gramma rays 1
    Mustard gas 1
19.  
    1. Substitution1
    2. Deletion 1

20. Lack of bile salts; which emulsify fats;

21. High auxin concentration produced by terminal bud/ apical meristem, inhibits lateral buds growing into branches; removal of terminal bud/ apical bud lowers the concentration of auxins/ lowers the inhibition effect (hence sprouting of lateral buds;

22.  
    1. - Its cells (vessels) have no transverse walls thereby forming a long hollow tube running from roots to leaves (through which water and mineral salts can easily be transported);
       - Have dead cells lacking nucleus and other cell contents (organelles) which might have otherwise retarded / restricted the movement of mineral salts and water from the soil through the roots and up the plant;
       - The cells are longitudinally joined to each other to enhance easy movement of water and mineral salts up the plant;
       - The cells have side walls coated with light deposits which prevent leakage of water and also strengthen the walls preventing them from collapsing;
       - The xylem vessels are narrow to facilitate capillarity;                                  OWWTTE
    2. - The epidermis is one cell thick for faster movement of water and mineral salts into the plants body;
       - They are thin and flexible to easily penetrate through the soil particles.
       - The root hairs are many to increase the surface area for diffusion of material into the plant;
       - Have semi-permeable membrane for selective movement of materials into the plant;

23.  
    1.  
       1. A group of organisms that can naturally/ freely interbreed to produce viable fertile young ones; (offspring) (1mk)
       2. (A scientific system of double naming) naming organisms using the generic/ genus and specific/ species names; OWWTTE               (1mk)

24. - Sodium pump mechanism in nervous system;
    - Reabsorption of useful materials in blood stream from tissue fluid;
    - Excretion of waste products from body cells;
    - Absorption of digested food/ mineral salts/ vitamins from alimentary canal;
    - Reabsorption of glucose / (some) salts in the kidney/ by kidney tubules;

25. When biceps contract it pulls the fore arm and the arm bends; the triceps relaxes to bring about balanced movement; when triceps contract the biceps relaxes and the fore arm stretches/extends;