Biology Paper 3 Questions and Answers with Confidential - Momaliche Joint Pre Mock Exams 2022

• Answer all the questions in the spaces provided.

1. You are provided with iodine solution, Benedict’s solution, visking tubing, test tubes, a beaker and a solution labelled X ( shake thoroughly before use)
   1. Using the reagents provided test the identity of solution labeled X. (6 mrks)
      

      Food test	Procedure	Observation	Conclusion

      Tie one end of the visking tubing provided with a thread tightly. Measure 5ml of solution X. Pour 5ml of solution X into the visking tubing. Tie the other end of the tubing tightly. Ensure there is no leakage. Rinse the outside of the tubing with distilled water and immerse it with its contents in a beaker containing iodine solution. Allow it to stand for 20 minutes.
   2.  
      1. Record your observation at the beginning and end of the experiment. Record your results in the table below. 
         (4 mrks)
         

         Experimental set up	Solution X  inside the visking tubing	Iodine solution outside the visking tubing
         Beginning of experiment
         End of experiment

      2. Suggest the nature of visking tubing. (1 mrk)
      3. Account for the results obtained in a (i) above. (4 mrks)
   3. Which physiological process was being investigated in this experiment? (1 mrk)
2. You are provided with specimens labelled:
   • J: Hibiscus rosaninensis
   • K: Bougainvillea glabra
   • L: Jacaranda mimosifolia
   • M: Zea mays
   • N: Lantana camara
     1. Using the characteristics given below and in the order  in which they occur, construct a dichotomous key to identify the specimens.(8mks)
        Characteristics
        1. Type of leaf
        2. Leaf venation
        3. Leaf margin
        4. Texture of leaf lamina
     2.  
        1. Identify the likely habitat  of  the plant from which specimen labelled N was obtained from. (1 mrk)
        2. Give a reason for your answer in bi) above. (1 mrk)
     3.  
        1. Name the class of the plant from which specimen M belong. (1 mrk)
        2. Give a reason for your answer in c i) above. (1 mrk)
3. Below are photographs labelled J and K of organs obtained from different animals. Examine them and answer the following questions.
   
   1. Identify the organs labelled: (2 mrks)
      1. X:
      2. Y:
   2.  
      1. State the function performed by the above named organs. (2 mrks)
         1. Organ X:
         2. Organ Y:
      2. State three adaptations of organ labelled Y to its function. (3mrks)
   3.  
      1. Identify the parts labelled 1, 2 and 3 in photograph K.(3 mrks)
      2. Using observable features, state how the parts labelled 1 and 3 you identified in (i) above are adapted to their functions. (2 mrks)

CONFIDENTIAL

Each candidate should have the following:

• 80 ml of iodine solution supplied with a dropper
• 8 cm visking tubing.
• 2 pieces of strong cotton thread 20 cm long.
• 100 ml beaker (glass or plastic)
• Means of timing. A wall clock will be appropriate.
• 10 ml measuring cylinder. 
• 100 ml water is 250 ml beaker.
• 10 ml of 10 % Starch solution labelled X.
• 10 ml of Benedict’s solution supplied with a dropper
• 2 Test tubes
• Hand lens
• Specimen
  • J: Hibiscus rosaninensis
  • K: Bougainvillea glabra
  • L: Jacaranda mimosifolia
  • M: Zea mays
  • N: Lantana camara

Preparation of 10 % Starch solution

• Dissolve 10 gm of starch powder in 100 ml of distilled water.

MARKING SCHEME

1.  
   1.  
      

      Food test	Procedure	Observation	Conclusion
      Starch;	To solution X add 2 drops of Iodine solution;	Solution turns Blue-black colour;	Starch present;
      Reducing sugar;	To solution X add Benedicts solution and heat;	Solution retains blue colour	Reducing colour absent;

      Food substance 1 mrk each
      Procedure, observation and conclusion ½ mrk each
      Total: Max (6 mrks)
      Rej wrong spelling of food substance and award  0 mrk
      Rej observation and conclusion if procedure is wrong
   2.  
      1.  
         

         Experimental set up	Solution X  inside the visking tubing	Iodine solution outside the visking tubing
         Beginning of experiment	White/cream; Rej. yellow	Yellow/Brown; Rej. Red
         End of experiment	Solution turns Blue-black;	No colour change/Yellow/Brown;

         4 mrks
      2. Semi-permeable; 1 mrk
      3. Iodine (molecules) moved into starch solution/solution X across the tubing through diffusion ; turning it blue-black; Starch (molecules) were too large such that they could not  move across the tubing into iodine solution;  3 mrks
   3. Diffusion; 1 mrk
2.  
   1. 1a.Simple leaf present………………………………….go to 2;
        b. Compound leaf present…………………………….. Jacaranda mimosifolia;
      2a.Parallelvenation present…………………………… Zea mays;
        b. Network venation present………………………….go to 3;
      3a.Serrated leaf margin present………………………go to 4;
        b. Smooth/ Entire leaf margin present………………. Bougainvillea glabra;
      4a.Smooth leaf lamina present…………………………go to 5;
         b. Hairy leaf lamina present……………………………. Lantana camara;
      rej if not scientifically written
      Each correctly identified leaf 1mrk = 4mrks
      Each correct statement 1/2X8=4mrks
      Total (8 mrks)
   2.  
      1. Habitat: Arid/semi arid; ( 1mrk)
         Rej Xerophyte
      2. Has tiny hairs on lamina to trap water vapour from the leaf cells thereby lowering saturation deficit and hence minimize water loss;  First 1 (1mrk)
   3.  
      1. Monocotyledonae; (1 mrk) rej small m
      2.  
         • Has parallel venation;
         • Has a leaf sheath; rej sheath alone
         • Is long and narrow;   First 1 ( 1mrk)
3.  
   1.  
      1. Y: Trachea;
      2. X: Lung; (2 mrks)
         rej lungs
   2.  
      1.  
         1. Organ X: Passage of air; (1 mrk)
         2. Organ Y: Gaseous exchange; (1 mrk)
      2.  
         • Has numerous air sacs called alveoli to increase surface area for gaseous exchange;
         • Alveoli is moist to dissolve gases;
         • Alveoli surrounded by a single layer of epithelial cells to shorten diffusion distance for faster diffusion of gases;
         • Alveoli highly vascularised to carry away respiratory gases;
           First 3 (3mrks)
           Rej lungs are numerous. Must mention presence of alveoli.
   3.  
      1.  
         • 1:Gill rakers; rej wrong spelling
                                  rej singular
         • 2: Gill bar;
         • 3: Gill filaments; rej singular
      2.  
         • 1: Teethed/ forked to trap solid particles to protect the delicate gill filaments; (1 mrk)
         • 3:
           • Has numerous to increase surface area for gaseous exchange;
           • Moist to dissolve gases;
           • Surrounded by a single layer of epithelial cells to shorten diffusion distance for faster diffusion of gases;
           • Highly vascularised to carry away respiratory gases;
             Any 1 (1 mrk)