Biology Paper 3 Questions and Answers with Confidential - Bondo Mocks 2021 Exams

• Answer all questions in the spaces provided.
• You are required to spend the first 15 minutes of the 1¾ hours allowed for this paper reading the whole paper carefully before commencing you work
• Candidates should answer the questions in English.

1. You are provided with solid Q and R. You are also provided with iodine solution, Sodium hydroxide solution and Copper (II) sulphate solution.
   1. Dissolve all solid Q in 5cm³ of distilled water in a test tube to form a suspension. Label it as Q.
   2. Dissolve all solid R in 5cm³ of distilled water in a test tube to form a suspension. Label it as R.
      1. Using the procedure outlined in the table below, carry out food tests on the substances Q and R, write the food, observation and conclusion. (6 marks)
         

         Food	Procedure	Observation	Conclusion
         	To 2ml of Q in a test tube, add 3 drops of iodine solution
         	To 2ml of Q in a test tube, add equal amounts of Sodium hydroxide solution then followed by a few drops of Copper (II) sulphate solution and shake
         	To 2ml of R in a test tube, add 3 drops of Iodine solution
         	To 2ml of R in a test tube, add equal amounts of Sodium hydroxide solution then followed by a few drops of Copper (II) sulphate solution and shake

      2.  
         1. Which of the two substances should be included in a diet to protect a child from suffering Kwashiorkor. (1 mark)
         2. Give a reason for your answer in b (i) above.     (1 mark)
      3.  
         1. Name two enzymes in the human body which digest the food substances found in Q. (2 marks)
         2. State the organ from which each of the enzymes you have stated in c(i) above acts. (2 marks)
            Enzyme:....................................................... Organ…………………...........................................
            Enzyme: ..................................................... Organ: .......................................................................
2. You are provided with specimen Y.
   1.  
      1. Using external features only, identify the part of the plant. (1 mark)
      2. Give two reasons for your answer in a(i) above. (2 marks)
   2. State the class to which the specimen belongs and give one reason for your answer. (2 marks)
   3.  
      1. Explain two observable features in the specimen that adapt it to nutrition.     (2 marks)
      2. State two features of the specimen that is only observable under a microscope that adapts it to gaseous exchange. (2 marks)
3.  
   1. The photograph below shows an experiment that was set to investigate a certain process in been seedling.
             
      1. Identify the response being investigated. (1 mark)
      2. Account for the observed results for the seedling A after 24 hours. (4 marks)
      3. Explain why the root in the seedling B continued to grow straight downward. (2 marks)
      4. Explain the significance of the response stated in a(i) above to plant. (2 marks)
   2. You are provided with the photograph of mammalian bones P and Q obtained from the same animal.
      
      1. Name bone
         P: ………………........................................................ (1 mark)
         Q: ………………....................................................... (1 mark)
      2. State the part of the body from which the bones were obtained.
         P: ................................................................................ (1 mark)
         Q: ............................................................................... (1 mark)
      3. Which two of the labeled parts forms a ball and socket joint. (1 mark)
      4. With reasons identify the type of joint formed by bone P at:
         
         1. Distal end: ............................................................................ (1 mark)
            Reason: ................................................................................................................... (1 mark)
         2. Anterior end: ........................................................................ (1 mark)
            Reason: ................................................................................................................... (1 mark)
      5. Name the other bone that articulates with bones P and Q and controls or limits movement in man.

CONFIDENTIAL

1. Solid Q
2. Solid R
3. 20ml distilled water
4. 2 labels
5. 6 test tubes in a rack
6. Specimen Y
7. 10ml measuring cylinder

Each student to have access to the following reagents;

1. Iodine solution
2. NaOH
3. 1% CuSO₂

Preparations

1. Solid Q, Wheat flour. Weigh 1g of wheat flour and label it Solid Q.
2. Solid R, Maize flour. Weigh 1g of maize flour and label it Solid R.
3. Specimen Y is a leaf of kales (Sukuma Wiki)

MARKING SCHEME 

1.  
   1.  
      

      Food	Procedure	Observation	Conclusion
      Starch✓ ½	To 2ml of Q in a test tube, add 3 drops of iodine solution	Blue-black colour formed ✓ ½	Starch present ✓ ½
      Protein ✓ ½	To 2ml of Q in a test tube, add equal amounts of Sodium hydroxide solution then followed by a few drops of Copper (II) sulphate solution and shake	Purple colour formed ✓ ½	Protein present ✓ ½
      Starch✓ ½	To 2ml of R in a test tube, add 3 drops of Iodine solution	Blue-black colour formed ✓ ½	Starch present ✓ ½
      Protein ✓ ½	To 2ml of R in a test tube, add equal amounts of Sodium hydroxide solution then followed by a few drops of Copper (II) sulphate solution and shake	Blue colour of CuSO4 persist✓ ½	Protein absent ✓ ½

      Total = 6 marks
   2.  
      1. Q  ✓1
      2. It contains proteins ✓1
   3.  
      1. Salivary amylase/Ptyalin/Pancreatic amylase
         Pepsin/Trypsin ✓1
      2. Enzyme- Salivary amylase Organ- mouth ✓1  both matched correctly
         Enzyme- Pancreatic amylase Organ- Duodenum// Small intestine ✓1
         Enzyme – Pepsin Organ- Stomach ✓1
         Enzyme- Trypsin Organ- Duodenum// Small intestine ✓1
2.  
   1.  
      1. Leaf ✓1
      2.  
         • Presence of  leaf blade/lamina
         • Presence of petiole/leafstalk/midrib
         • Presence of veins       Any first two ✓1 each
   2. Class - Dicotyledonae✓1
      Reason
      • Network venation
      • Presence of petiole
      • broad leaves
   3.  
      1.  
         • Broad flat lamina- to increase the SA for absorption of CO2 and sunlight for photosynthesis.
         • Thin lamina- it shorten the distance for sunlight and CO2
         • Extensive veins to increase the SA for transportation of mineral salts and water for photosynthesis.
      2.  
         • Has Stomata which allows exchange of gases
         • Has intercellular air spaces which enable free circulation of air inside the leaf.
3.  
   1.  
      1. Geotropism✓1
      2. Auxins migrate to the lower side of the root/radical due to gravitational pull ✓1; High concentration of Auxins in the roots inhibits growth✓1;  hence cells on the upper side of the root with low concentration of Auxins elongate✓1 faster  than those at the lower side hence the root curved downwards.
      3. Gravitational pull was acting uniformly on the root tip,; hence no unequal distribution of Auxins. ✓1
      4. Enable roots to grow downwards into the soil so as to provide anchorage✓1 and to access water and mineral salts✓1
   2.  
      1. P- Humerous✓1 rej wrong sp
         Q- Scapula✓1 acc shoulder blade
      2. P-  upper arm/upper forelimb/upper foreleg
         Q- shoulder/pectoral region
      3. 2 and 3✓1
      4.  
         1. Hinge joint ✓1 Presence of troch /ear groove cochlea that fits into trochlea notch/sigmoid notch of ulna.
            • It allows movement in one plane, 180°
         2. Ball and Socket joint✓1 – Presence of ball shaped head/rounded head that fits into the cup shaped glenoid cavity of the scapula.
            • It allows movement in all planes/directions 360°
      5. Clavicle✓1