Biology Paper 3 - 2021 KCSE Prediction Questions and Answers Set 1

Instructions to Candidates

1. Answer all the questions.
2. You are required to spend the first 15 minutes of the 1¾ hours allowed for this paper reading the whole paper carefully before commencing your work.
3. Incorrect spellings of Especially technical terms may be penalized.
4. Candidates should answer the questions in correct English.

1. You are provided with;
   • One Irish potato
   • A cork borer
   • Solution P
   • Solution Q
   • 3 Petri dishes
   • Tissue paper
   • 3 labels.
     1. Make three Irish potato cylinders each measuring 30mm in length. Place one cylinder on an empty Petri dish, one cylinder in solution P on a Petri dish and the other in solution Q on a Petri dish. Label the three Petri dishes as Air, P and Q respectively leave the set-ups to stand for 30 minutes. After 30 minutes, feel each cylinder with your fingers for texture and flexibility. Record your observation in the table below.                                                        (6mks)
        

        Cylinder in	Texture	Flexibility
        Air Solution P Solution Q

     2. Remove each cylinder from the solution (after 30 minutes). Wipe each with a tissue paper and measure their lengths again. Also measure the length of the cylinder placed in air. Record your measurements in the table below. Work out the percentage change in length and record in the last column.       (6mks)
        

        Cylinder in	Initial length	Final length	% change
        Air Solution P Solution Q	30mm 30mm 30mm

     3. From your results in (a) and (b) above state the nature of solutions P and Q in relation to the potato cells.
        Solution P 
        Solution Q (2mks)
     4. Why was the potato cylinder placed in air included in the experiment? (1mk)
     5.  
        1. Account for the change in length of the potato cylinder placed in solution P. (3mks)
        2. Account for the change in length of the potato cylinder placed in solution Q.    (3mks)
           
           
     6.  
        1. Name the physiological process that was taking place in this experiment. (1mk)
        2. State the importance of the physiological process that you have named in f (i) above to plants.    (3mks)
     7.  
        1. What would happen if the potato cylinders were first boiled before putting them in solutions P and Q? (1mk)
        2. Give a reason for your answer in g (i) above.                                                                (2mks)

2. You are provided with specimen L and a hand lens.
   1.  
      1. Draw and label the external parts of specimen L. (2mks)
      2. Work out magnification.                                                                                             (1mk)
   2. What is the significance of total surface area of the leaf to the plant? (1mk)
   3. How is specimen L adapted to perform its functions? (3mks)

3. You are provided with specimen S. Observe specimen S carefully.
   1. With a reason, state the agent of dispersal for specimen S.
      Agent (1mk)
      Reason(1mk)
   2. Make a transverse section of specimen S.
   3.  
      1. Name the type of placentation in specimen. (1mk)
      2. Name the type of reproduction exhibited by specimens S.                                                     (1mk)
      3. Give a reason for your answer in b (ii) above.                                                                         (1mk)

MARKING SCHEME

1.  
   1.  

      Cylinder in	Texture	Flexibility
      Air Solution P Solution Q	Fairly rough; Very rough; Soft/ smooth ;	Fairly flexible; Rigid/stiff; Very flexible;

             (6mks)
   2.  

      Cylinder in	Initial length	Final length	% Change
      Air Solution P Solution Q	30mm 30mm 30mm	30mm; 32+1 mm; 28+ 1 mm;	0%; ×100 = 6.67; × 100 = 6.67%;

        (6mks)
   3. Solution P – Hypotonic / less concentrated;
      Solution Q – Hypertonic / more concentrated;    (2mks)
   4. To act as a control experiment;             (1mk)
   5.  
      1. Solution P is hypotonic / less concentrated than the potato cells, water molecules move into the potato cells by Osmosis through their cell membranes (that are semi- permeable ); making the cells turgid to increase the length of the cylinder;                             (3mks)
      2. Solution Q is hypertonic/ more concentrated than the potato cells, therefore water molecules moved out of the potato cells by osmosis through their (semi-permeable) cell membranes; making the cells flaccid, hence a decrease in the length of the cylinder  (3mks)
   6.  
      1. Osmosis     (1mk)
      2.  
         • Absorption of water by root hairs from the soil;
         • Plays a role in the opening and closing of stomata;
         • Makes plants cells turgid, thus giving support to herbaceous plants;
         • Plays a role in the movement of absorbed water across the cortical cells of the roots to the xylem;
         • Plays a role in feeding of insectivorous plants such as venus fly trap; (Max. 3 mks)
   7.  
      1. There would be no change in length;                                                                          (1mk)
      2. Boiling kills the potato cells; and denatures their cell membranes;                          (2mks)

2.  
   1. Magnification = =X1 – X3    (1mk if formula is indicated.
   2. A larger surface area means efficient photosynthesis, gaseous exchange and transpiration; (1mk)
   3. Broad and flat to increase surface area over which photosynthesis and gaseous exchanges take place;
      Thin lamina to educe the distance over which carbon (iv) oxide and light rays reach photosynthetic cells;
      Presence of chloroplast to trap light energy for photosynthesis;
      Presence of veins and midrib for support to keep the lamina flat;
      Presence of veins which have vascular bundles for transportation of synthesized food to other parts   .     and water from the roots to the leaves;
      Has a petiole for attachment onto the stem and for holding it in a position to trap maximum light;
      (max 3mks)

3.  
   1. Agent : Animal;
      Reason: Brightly colored to attract animals;
      Succulent/ fleshy to be eaten by he animal;
      Large and conscious to be easily seen by the animals;
   2.  
      1. Axile;
      2. Sexual reproduction;
      3. Presence of viable seeds;

CONFIDENTIAL
REQUIREMENTS

Each student will require:

1. Cork borer 3mm in diameter
2. An Irish potato (medium size)
3. 3 Petri dishes
4. Tissue paper
5. Distilled water solution labeled solution P (25mls)
6. Concentrated Salt solution Q (25mls)
7. 3 labels
8. A fresh Bougainvillea leaf labeled L.
9. A ripe tomato fruit labeled S.
10. A scalpel
11. A hand lens.
12. A 30cm plastic ruler.