Biology Paper 3 Questions and Answers - Achievers Joint Mock Exams 2023

INSTRUCTIONS TO CANDIDATE

1. Answer all the questions
2. You are required to spend the first 15 minutes of 13/4 hours allowed for this paper reading the whole paper carefully before commencing your work.
3. Candidates may be penalized for recording irrelevant and incorrect spelling especially of technical terms.

FOR EXAMINERS USE ONLY.

QUESTIONS

1. Use the photograph of mammalian digestive system and associated organs to answer the questions that follow.
   1.        
      1. Name the structures named , (4mrks)
         
      2. Name an acid found in the structure labelled K. (1mrk)
      3. Name the juice stored in the structure labelled B and give its function. (2mrks)
         Juice
         Function.
      4. In the photograph, identify with letter D where the function named in (iii) above takes place (1 mrk)
   2. Use the the photograph of the mammalian blood component to answer the questions that follow.
      
      
      1. Identify the blood component. (1mrk)
      2. Name two structural adaptations of the blood component named in b (i) above to its function. (2mrks)
      3. Name a hereditary disease caused by the structure labeled M in the photograph. (1mrk)
      4. Explain what would happen to the blood components once they are placed in a concentrated salt solution. (2mrks)
2. Use the photographs on plant response to answer the following questions.
   
   
   1. Name the type of response shown in the photographs. (1mrk)
   2. What is the survival value of the response shown? (1mrk)
   3. Explain how the response occurs. (3mrks)
3. Use the photographs on plant structures to answer the following questions.
   
   
   1. Name the plant structure shown in the photographs. (1mrk)
   2. Name the part of the plant where the structure shown in the photos is found abundantly in terrestrial plants. (1mrk)
   3.  Give the function of the structure named in 2(i) above. (1mrk)
   4. Observe photograph F carefully. Give three structural adaptations of the structure to its functions. (3mrks)
   5. Explain what would happen to the plant structures if they are placed in a hypotonic solution (3mrks)
4.            
   1.  You are provided with solution Z . Divide it into three portions. Use one portion of Z, Benedict’s solution, iodine and a source of heat to carry out food tests.(8mrks)
      

      Test	Procedure	Observations	Conclusion

   2. Measure one ml of DCPIP and put it in a test tube. To it add drops of the second portion of Z and record how many drops decolorizes DCPIP (1mrk)
   3. Boil the third portion of solution Z for two minutes. Repeat the procedure in (b) above and record the number of drops that decolorizes DCPIP (1mrk)
   4. Account for the difference in the number of drops used to decolorize DCPIP. (2mrks)

MARKING SCHEME

1.                
   1.              
      1. A Liver
         R Gall bladder
         K Stomach
         T Bile ducts
      2. Hcl / Hydrochloric acid
      3. Bile
         Emulsify fats to increase their surface area for digestion
      4.          
                
   2.              
      1. Red blood cell
      2.              
         • biconcave disc shape to increase their surface area for oxygen transportation.
         • Lack nucleus and other cell organelles to increase the surface area for packaging more oxygen.
         • Has haemoglobin which has a high affinity for oxygen.
         • Thin plasma membrane to reduce the distance through which gases diffuse.
      3. Sickle cell anemia
      4. The blood cell looses water through osmosis; shrink; and become crenated;
2.              
   1. Thigmotropism / haptotropism.
   2. Enable plants to climb to increase chances of obtaining sunlight for photosynthesis.
   3. Contact; influences migration; of auxins away from it; the side in contact with the plant has less auxins than the outer side; hence cell elongation is more than the side in contact; causing curving towards point of contact.; (6marks max 3 mrks).
3.            
   1. Guard cells
   2. Lower side of leaf
   3. Opening and closing of the stomata
   4.  
      • Thin elastic outer wall to enable the guard cell bulge out when turgid to open the stomata
      • Crescent / bean shaped to create a pore at the centre ( stoma)
      • Presence of chloroplasts to trap sunlight energy for photosynthesis max-3mrks
   5. Water gets into the plant cell through osmosis; swells; and becomes turgid
4.                  
   1.                 
      

      Test	Procedure	Observations	Conclusion
      Reducing sugars;	To food/z add Benedict’s sln and heat;	No colour change; Rej. No change	Reducing sugars absent;
      Starch;	To food/ z add iodine;	No colour change; Rej. No change	Starch absent;

      Rej. No change Starch absent;
   2. 3 Drops
   3. 8 drops
   4. High temperatures; destroy vitamins;