Biology Paper 3 Questions and Answers - KCSE 2022 Prediction

INSTRUCTIONS TO CANDIDATES

1. Answer all the questions in the spaces provided.
2. You are required to spend the first 15 minutes of the 1³/₄ hours allowed for this paper reading the whole paper carefully before commencing your work.
3. Candidates should answer the questions in English.

Questions

1. You are provided with solution L ,starch solution and sodium chloride in two different concentrations 0.05% and 1.4%. Place 3 ml of starch solution in test tubes labeled 1,2 and 3. Add 3 drops of 0.05% sodium chloride to the test tube labeled 2.Then; add 3 drops of 1.4% sodium chloride to the test tube labeled 3. Add 3 ml of solution L to each of the test tube labeled 2 and 3.
   1. Place a drop of the contents from each test tube 1, 2 and 3 on white tile. To each drop, add iodine solution. Record your results in the table below.(3mks)
      

      Test tube	Observations at the start of the experiment	Observations at the end of the experiment
      1
      2
      3

   2. Place the test tubes in a water bath maintained at 37°C and allow to stand for 30 minutes. Place a drop of the contents from each test tube on a white tile. To each add a drop of iodine solution. Record your observation in the table above. (3 marks)
   3. Add equal amounts of the Benedict’s solution to test tubes labeled 2and 3; heat to boil.
      Record your observation.
   4. Why was the test tube labeled 1 included in the experiment? (1 marks)
   5. Account for the results in tubes 1, 2 and 3. (3 mark)
   6. Suggest the identity of solution L. (1 mark)
   7. Why were the test tubes placed in water bath maintained at 37°C (1mk)
2. You are provided with photograph M and N below. Examine them.
   
   
   1. With reasons, name the class to which each of organisms belongs. (4 marks)
      

      Organism	Class	Reason
      M
      N

   2. State two similarities and one difference in the two species.
      1. Similarities- (2 marks)
      2. Difference- (1 mark)
   3. Based on external features, suggest the habitat of the animal in photograph M and state your reasons.
      1. Habitat: (1 mark)
      2. Reasons: (3 marks)
3. You are provided with plant specimens labelled P, R, T and Y
   
   1. Using the features in the order given below, construct a dichotomous key that can be used to identify with letters the specimens provided. (8 marks)
      • Simple or compound leaf
      • Leaf venation
      • Leaf margin
      • Leaf colour
   2. Explain how specimen T is adapted to its mode of pollination (3 marks)
   3.    
      1. Using floral parts only of specimen T, state the class to which it belongs. (1mark)
      2. Give a reason for your answer in (c) (i) above. (1mark)

CONFIDENTIAL

• About 3ml of solution L- enzyme diastase per student About 3ml of 0.05% NaCl solution with a dropper
• About 3ml of 1.4% NaCl solution with a dropper About 10ml of starchsolution per student
• 3 test tubes
• Measuring cylinder (5 ml or 10 ml) White tile
• Iodine solution with a dropper Benedict’s solution with a dropper Test tube holder
• Warm water bath maintained between 35-38°C Thermometer
• Means of labeling for the three test tubes 1 dropper
• Test tube rack Hibiscus leaf labelled P
• Tradescantia leaf labelled R
• Bougainvillea twig with a flower labelled T Maize/ Grass leaf labelled X
• Bidens pilosa leaf labelled Y

Marking Scheme

1.    
   1. (3 marks)
      

      Test tube	Observations at the start of the experiment	Observations at the end of the experiment
      1	Blue black /black	Blue black /black
      2	Blue black /black	Retained color of iodine /brown yellow. Acc. Traces of black
      3	Blue black /black	Retained iodine color /brown/yellow

   2. Test tube 2
      - Changes to green/yellow (1 mark)
      Test Tube 3
      - Colour changes to orange/brown (1 mark)
   3. Control experiment (1 mark)
   4. starch was broken down/hydrolyzed/converted to sugars/reducing sugar/maltose in test tubes 2 and 3.
      
      • Starch was not broken down/converted into reducing sugar in test tube/due to lack of sodium chloride and solution L (enzyme); more reducing sugar in test tube 3 than test tube 2; due to higher concentration of sodium chloride; sodium chloride accelerates hydrolysis of starch. (4 marks)
   5. enzyme/diastase (1 mark)
   6. Provide optimum temperature/best temperature for enzyme activity. (1 mark)
2.        
   1. 
      

      Organism	Class	Reason
      M	Insecta	-Body is divided into 3 parts ; head, thorax and abdomen; -Have 3 pairs of legs
      N	Insecta	-Body is divided into 3 parts ; head, thorax and abdomen; -Have 3 pairs of legs

   2. Similarities. Both have:
      • Body is divided into 3 parts; head, thorax and abdomen
      • Have one pair of antennae;
      • Have 3 pairs of legs
      
      Differences:
      
      • M has 2 pairs of wings, N has one pair of wings;
      • M has a brown colour, N has black and yellow stripes;
      • M has smooth body, N has hairy body;
   3. Habitat: cracks and crevices
      Reasons:
      
      • Dorsal –Ventrally flattened body enabling it to fit into cracks and crevices
      • Legs are ventrally placed for fast movement and are easily folded under the body enabling entry into cracks and crevices
      • Smooth forewing to reduce resistance while gliding through cracks and crevices
      • Brown/dark brown body colour for camouflage.
3.  
   1. 1(a) Leaf simple.......................................................... go to 2
      1(b) Leaf compound.................................................... Y
      2(a) Leaf has network venation................................... go to 3
      2(b) Leaf has parallel venation ................................... go to 4
      3(a) Leaf margin smooth/ entire .................................. T
      3(b) Leaf margin serrated. ........................................... P
      4(a) Leaf purple.............................................................R
      4(b) Leaf green............................................................. X
      
       Rj 1(i)1(ii), i(a) i(b), Rj two for 2 in steps, ....go to.Must be there (8 marks)
   2. Brightly coloured bracts/conspicuous bracts; to attract insect pollinators; Tubular corolla;to be reached by visiting insects/ anther and stigma enclosed inside the tube; landing platform for insects pollinators; (3 marks)
   3.    
      1. Dicotyledonae; Rj wrong spellings (1 mark)
      2. Floral parts are in fives; Rj multiples of fives acc. Correct no. of named floral part.(1 mark)