BIOLOGY PAPER 3 - 2019 KCSE STAREHE MOCK EXAMS (QUESTIONS AND ANSWERS)

INSTRUCTIONS TO CANDIDATES

• Answer ALL questions in the spaces provided in the question paper.
• You are not allowed to start working with the apparatus for the first 15 minutes of the 1 3/4 hours allowed for this paper. This time is to enable you to read the question paper and make sure you have all the chemicals and apparatus that you may need.

1. The diagram below shows bones obtained from the same mammal.
   
   
   1. Give the identity of each of the above bones.                                           (4 marks)
   2. Draw a diagram of the bones, arranged as they appear in the mammal from which they were obtained from.   (3 marks)
   3. On your diagram indicate by naming the types of joints between the bones. (2 marks)
   4.  
      1. Give three adaptations of bone labeled 3 to its functions.                  (3 marks)
      2. Give three adaptations of bone labeled 4 to its functions                  (4 marks)

2. You are provided with solution labeled J, use the reagents provided to test for the food  substances.
   1. Use the iodine solution to test for the food substance in solution J.
      1. Food substance  (1 mark)
      2. Procedure        (1 mark)
      3. Observation    (1 mark)
      4. Conclusion     (1 mark)
   2. Use Benedict’s solution to test for the presence of the food substance in solution J.
      1. Food substance    (1 mark)
      2. Procedure          (1 mark)
      3. Observation       (1 mark)
      4. Conclusion      (1 mark)
   3. Use DCPIP solution provided to test for the presence of the food substance in solution J
      1. Food substance   (1 mark)
      2. Procedure          (1 mark)
      3. Observation        (1 mark)
      4. Conclusion        (1 mark)
   4. When testing for non-reducing sugars explain the role of the following substances.
      1. Dilute hydrochloric acid.      (1 mark)
      2. Sodium hydrogen carbonate    (1 mark)

3. Study photograph labeled V which is a display of internal organs of a small mammal. Photograph F is an inset of internal structure of part labeled L. Study them carefully.
   
   
   1. Name the part of the mammalian body where the organs shown in the photograph are found.   (1 mark)
   2. Identify the organ system that consists of parts J and L in the photographs.      (1 mark)
   3.  
      1. Name the parts labelled J and K.       (2 marks)
      2. Give the function of the part labelled G.     (1 mark)
   4. State two adaptations of organ in L to its functions   (2 marks)
   5. F (a) is an inset of the internal structure of part L showing the position of the functional units of L. One of these functional units is shown in the inset F (b).                      
      1. Identify the functional unit shown in inset F(b) and give its function.             (2 marks)
         Identity:
         Function:
      2. Give one observable feature in the structure you have named in (e)(i) above that adapt it to its function.     (1 mark)

MARKING SCHEME 

1.  
   1. 1          -           Ulna
      2          -           Radius
      3          -           Scapula
      4          -           Humerus
   2.  
       
   3.   
      1.  
         • Broad and flattened surface to provide a large surface area for attachment of shoulder muscles; rej flat
         • Has a spine to increase surface area for muscle attachment;
         • Has a glenoid cavity for articulating with the head of humerus; rej joining for articulation
         • Has coracoid process for attachment of ligaments that connect it to the humerus;   (Any three)      
      2.  
         • Has a long shaft to act as a lever for easy movement of the limb
         • Has a long shaft to provide a large surface area for attachment of biceps and triceps muscles;
         • Has a head (ball) for articulating with the scapula to form a ball and socket joint;
         • Has trochlea at one end for articulating with the sigmoid notch of the ulna;
         • Has olecranon fosa into which the olecranon process on the ulna fits to stop overstretching of the lower arm backwards. (Any 2)

2.  
   1.  
      1. Food substance;          Starch;
      2. Procedure;                   Add iodine solution to J
      3. Observation;             Blue- Black/ black/ blue colour is observed; rej. Bluish/blackish
      4. Conclusion;                 Starch present;
   2.  
      1. Food substance;          Reducing sugar
      2. Procedure; To solution J, add Benedict’s solution, Boil Rej . benedicts/Benedicts, warm for boiling ( in a water bath) 
      3. Observation;                The colour remains blue/ blue colour persists; rej No Change
      4. Conclusion:                 Reducing sugar absent;
   3.  
      1. Food substance; Vitamin C/ Ascorbic acid;
      2. Procedure:       Add solution J into DCPIP; drop by drop. Rej. Without drop by drop
      3. Observation:    DCPIP is decolourised;
      4. Conclusion: Vitamin c/ Ascorbic acid present;
   4.  
      1. to hydrolise any disaccharide present.
      2. to neutralize excess hydrochloric acid. rej. Without excess.

3.  
   1. Thorax/Thoracic region/Thoracic cavity; Rej chest
   2. Gaseous exchange system; Rej Respiratory system.
   3.  
      1. J: Trachea; Rej wind pipe K: Diaphragm;
      2. Pumping blood to various parts of the body;
   4.  
      • Highly vascularised in alveoli for gases to diffuse and get transported;
      • Spongy to accommodate more air; Acc. elastic
      • Numerous alveoli to increase surface area for maximum gaseous exchange;
      • Well ventilated/connected to bronchus/bronchioles to allow free movement of gases in and out during breathing;
      • Has alveoli with moist lining where gases dissolve to facilitate gaseous exchange due to their rapid diffusion; (1^st two)
   5.  
      1. Identity: Alveolus; Rej alveoli, air sac
         Function: The surface in the lungs where gaseous exchange occurs;

      2. Highly vascularised for gases to diffuse into to enhance their transportation; Well ventilated to enhance movement of gases in and out; (1^st one)