Biology Paper 3 Questions and Answers with Confidential - Form 3 Term 3 Opener Exams 2023

 QUESTIONS

1. You are provided with food substance labeled solution A. The reagent provided are Iodine solution, Benedicts solution, 2M hydrochloric acid, Sodium Carbonate solution 1% Copper sulphate solution and 10% Sodium hydroxide solution.
   1. Perform food tests and fill in the table below.               (12 marks)
      
      

      Food substance	Procedure	Observation	Conclusion

   2. Name the enzyme responsible for digestion of food substance present in A in two named regions of the human alimentary canal. (2marks)
   3. Name a deficiency disease in children that may result from lack of one of the food  Substances in A. (1 mark)
2. Examine photographs labeled T and S given below and use them to answer the questions that follow.
                  
   1. Giving reasons, name the mode of nutrition of the mammals whose skulls are shown in the photographs.        (1mark)
      T………………………………………………. 
                 
      Reasons                  (2marks)
      …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
      S……………………………………………….                                           (1 mark)
      
      Reasons                       (2 marks)
      …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
   2. In the appropriate diagram, label the position where the horny pad would be found in living animals.         (1 mark)
   3. Name the part labeled Q and state its function in photograph T.
      Name………………………………………………………………… …………    (1 mark)
      Function…………………………………………………………………………    (1 mark)
   4. Explain how the part labeled R is adapted to its function.     (3 marks
3. Examine the seedlings below and use them to answer the questions that follow:
                     
   1. Name the parts labeled C, D, E and state their importance for the seedling.
      C:.....................................................................................................................................(1 mark)
      Importance……………………………………………………………………………………………………………………………………………………………………………………………………  (1 mark)
      D.................................................................................................................................... (1 mark)
      Importance……………………………………………………………………………………………………………………………………………………………………………………………………   (2marks)
      E...................................................................................................................................... (1mark)
      Importance……………………………………………………………………………………………………………………………………………………………………………………………………  (l mark)
   2. The seedlings labeled R1, R2, R3, and R4 later on develop swellings on their roots:
      1. What is the name of the swelling    (1mark)
      2. Name the organisms that would be found in the swellings    (1mark)
      3. Explain the relationship that exists between the named organisms and the plant (1mark)
          
   3. 1. State the type of germination exhibited by R series of the seedlings.      (1 mark)
      2. Give a reason for your answer in (c) (i) above.      (1 mark)
         
         
   4. State any two external factors necessary for germination.                                           (1 mark)

CONFIDENTIAL

Each candidate should be supplied with the following;

• 15ml solution labeled A
• Iodine solution
• Benedicts solution
• 2M hydrochloric acid,
• 10% Sodium hydroxide solution
• 1% Copper (II) sulphate
• Sodium Carbonate solution
• Small beaker
• Source of heat
• 4 test tubes

Solution A is prepared by adding albumen from 4 eggs in 500cm3 of water then added 50g of sucrose and stir the mixture thoroughly.

MARKING SCHEME

1.  
   1. Perform food tests and fill in the table below. (12 mks)
      
      

      Food substance	Procedure	Observation	Conclusion
      Starch	To about 2cm3 of A, add a few drops of iodine solution	No color change/brown color of iodine remains	Starch absent
      Reducing sugar	To about 2cm3 of solution A, add 2cm3 of benedicts solution and heat (to boil)	No colour change blue colour remains	Reducing sugar absent
      Non-Reducing sugar	To about 2cm3 of solution A add 1cm3 if 2m HCl and boil. Cool and NaHCO3 dropwise until fizzing stops add 1cm3 of Benedicts solution and heat	Colour changes to orange/orange precipitate formed	No reducing surgar present
      Proteins	To about 2cm3 of solution A, add 5 drops of 10% NaOH and shake. Then add 0.5% of copper (II) sulphate solution drop by drop while shaking.	Mixture turns purple	Protein present

   2.  
      1.  
         • In the stomach – enzyme pepsin              (2 mks)
         • In the duodenum – enzyme trypsin     
      2. Kwashiorkor           (1 mk)
2.  
   1.  
      1. T – Herbivorous
         Reasons
         • Presence of diastema
         • Lack of incisors in the upper jaw/presence of the horny pad
         • Lack of canines
      2. S – Carnivorous
         Reasons
         • Presence of long/curved/sharp/pointed canines for gripping/tearing/grasping/holding prey
         • Presence of carnassials teeth for cutting and crushing bone
   2. To be assessed by the teacher.
   3. Q- Diastema
      Functions:- allows for rolling of tongue during chewing/provides space for the tongue to manipulate vegetation during chewing.
   4. Adaptations of the part labeled R to its functions
      • Slide past each other/scissor-like to shear off/slice the flesh
      • Large/strong to crush bones
      • Have sharp edges for slicing the flesh from the bones.
3.  
   1. C – Hypocotyl       (1mk)
      Importance — protects the plumule /shoot tip/first foliage leaves /opens path through the soil for the cotyledon to pass/pulls the cotyledon out of the soil. Accept any one. Rj if wrong identity.
      
      D – Cotyledons/seed leaves (1mk)
      Importance: Photosynthesis (2mk)
      Food storage /food reserves
      Provide food for germinating seedlings /young plants.
      
      E – Coleoptile/plumule sheath Rej: cover/coat (1mk)
      Importance – protects the delicate tip/first leaves/foliage leaves (1mk) tie importance to identify 
   2.  
      1. nodules/root nodules  (1mk) accept correct spelling
      2. Rhizobium/Rhizobia/Rhizobium bacteria rej. Bacteria alone/wrong spelling
      3. Symbiotic relationship in which bacteria gets protection and nutrients while the plant gets nitrogen in form of nitrates fixed by bacteria. (1mk)
   3.  
      1. Epigeal (1mk) accept correct spelling.
      2. Cotyledons are brought out of the ground. (1mk)
   4. • Water      (1mk)
      • Oxygen
        
      • Optimum temperature   Rej temperature alone