Biology Paper 3 Questions, Answers and Confidential - Form 4 Term 2 Opener Exams 2022

• This paper consists of three questions
• Answer all the questions in the spaces provided.
• You are required to spend the first 15 minutes of the 13/4 Hours allowed for this paper reading through all the questions before commencing your work.

For Examiners Use Only

QUESTIONS

1. You are provided with a suspension labelled M.
   1. Using the reagents provided only, test for the food  substances present in the suspension. In the table below, record the food tested, procedure, observation and conclusions. 12 marks.
      

      Food TEST	Procedure	Observation	Conclusion

   2. Name two enzymes that may be required to digest suspension M in the alimentary canal  in human. (2mark)
   3. State role of the following in the experiment. (2marks)
      • sodium hydrogen carbonate
      • Dilute hydrochloric acid
2. Experimental evidence shows that most mutations results to variations among organisms.  The illustrations I, II, III and IV below show different possible types of chromosome mutations. Study them keenly.
   
   
   1. Identify the types of chromosome mutations illustrated.(4 marks) 
      Illustration          Name of mutation 
            I 
            II
           III
           IV
   2. State the effect of the mutation illustrated in III.   (1 mark)
   3. In most cases, the mutation in II could be lethal. Explain. (2 marks)
   4. During which stage of mitosis does the mutation in  I above occur?   (1 mark) 
   5.                            
      1. Define a mutation (1 mark)
      2. Give two possible environmental mutagens. (2marks)
3. The diagrams below represent body parts of some organisms (animals). Study them and answer the question that follow
   
   
   1.                        
      1. Suggest the type of food eaten by organisms with the parts labeled A, B, C and F
         Food                                   Reason
         A
         B
         C
         F                                                            (4mks)
      2. With reasons, suggest the likely habitat of the organism from which the parts labeled D and E were obtained
         Part                                      Habitat                                  Reason
         D
         E                                                                                                       (4mks)
   2.                      
      1. Suggest the type of evolution that is exemplified by the organisms labeled D, E and F. Give reason for your answer
         The type of evolution   (2mks)
         Reason
      2. Suggest the significance of the above named type of evolution for the organism (1mk) 
   3.                                
      1. Explain briefly the meaning of analogous structures   (1mk)
      2. Give one example of analogous structure (1mk)

MARKING SCHEME.

1.                                                        
   1.                         
      

      Food	Procedure	Observation	Conclusion
      Starch	put two millilitres of suspension M into a clean test tube. Add two drops of iodine solution and shake well.	Brown colour of iodine SOLUTION turns blue-black	starch  present;
      Reducing sugar	put two millilitres of suspension M into a clean test tube. Add of two millilitres Benedict’s solution, shake well and heat to boil Rej If Benedict’s is not in possessive form	The blue colour of Benedict’s solution remains Rej: no colour change	Reducing sugars  absent.
      Protein	put two millilitres of suspension M into a clean test tube. Add   two millilitres of sodium hydroxide solution and shake well. Slowly add 2 drops of Copper (II) sulphate solution and shake well.	On adding Copper (II) sulphate solution, a blue ring forms on the solution. On shaking, the mixture turns purple	proteins present.
      Vitamin C	put two millilitres of DCPIP solution into a clean test tube. Add  solution M dropwise while shaking.	The blue colour of DCPIP solution persist.	Vitamin C absent.

   2. Amylase.       Any two correct       2marks.
      Maltase.
      protease
   3. Sodium hydrogen carbonate. To neutralise excess hydrochloric acid.  1mark.
      Hydrochloric acid. To hydrolyse complex sugars (non-reducing sugars) to simple sugars (reducing sugars).  1 mark.
2.                        
   1. (4 marks) 
      Illustration          Name of mutation 
      I              Non -disjunction
      II              Deletion.
      III            Inversion.
      IV           Translocation
   2. Brings about reversing   the gene sequence thus enhancing advantageous or disadvantageous genes   (1 mark) 
   3. lethal since the offspring may lose genes responsible for the synthesis of some vital proteins (2 marks)
   4. During prophase (1 mark) 
   5.                      
      1. Random and spontaneous change in individual’s genetic makeup.  (1 mark)
      2. Very high temperatures.
         Radiations: alpha, gamma, beta, UV and X-rays
         Viruses: papilloma
         Heavy metals: mercury.  
         Any two correct answers (2marks)
3.                  
   1.                                                               
      1.                                        
         

         specimen	Food	reason
         A	Aquatic matter and Invertebrates	Wide shovel shaped beak
         B	Nectar	Long, thin beak
         C	Nuts	Short, thick strong beak
         F	Flesh	Strong sharp curved talons

      2.                                      
         

         part	Habitat	Reason
         D	Aquatic	Webbed feet for swimming / wading
         E	Tree branches	Long fingers / toes for perching

   2.                                           
      1. Divergent evolution
         Reason: similar basic structure and embryonic origin but modified into different forms / appearances (2mks)
      2. Enable the organisms / animals to utilize different ecological niches, to avoid competition for food. (1mrk)
   3.                            
      1. Structures with different embryonic origin but have similar function
      2.                            
         • Wings of birds and insects. (1mrk)
         • Eye of mammals and octopus. (mark one)

CONFIDENTIAL 

1. Each candidate should be supplied with the following
   1. 3 test tubes in test tube rack.
   2. Iodine solution – supplied with a dropper
   3. Adequate distilled water
   4. Benedicts solution– supplied with a dropper
   5. Means of heating
   6. 10% Sodium Hydroxide– supplied with a dropper 
   7. 1% Copper (II) Sulphate– supplied with a dropper
   8. DCPIP– supplied with a dropper
   9. 12cm³ of solution M in a boiling tube labeled as solution M