Biology Paper 3 Questions and Answers - Nyeri Mocks 2021 Exams

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INSTRUCTIONS

  • Candidates answer all questions in the spaces provided
  • Candidates should answer all the the questions in English.
  1. You are provided with iodine solution, visking tubing, a beaker and solution labeled X.
    Tie one end of the tubing provided with a thread tightly. Measure 5ml of solution X, pour 5ml of solution X into the visking tubing.
    Tie the end of the tubing tightly. Ensure there is no leakage. Rinse the outside of the tubing with distilled water and immerse its contents in a beaker containing iodine solution. Allow it to stand for 20 minutes.
    1.  
      1. Record your observation at the beginning and end of experiment. Record your results in the table below
         Experiment set up    Solution X inside the tubing   Iodine solution outside the tubing
         Beginning of experiment     
         End of experiment    
      2. What was the identity of solution X? (1mk)
      3. State the property of visking tubing. (1mk)
      4. Account for the results obtained in (a)(i) above (4mks)
    2.  
      1. Which physiological process was being investigated in this experiment? (1mk)
      2. State three factors which affects the process the process being investigated. (3mks)
  2. The picture below shows series of beaks in birds.
          NM2021 Bio PP3 ET2 Q2
    1. Using observable features in the photograph, place with reason, the class to which the above pictures belong
      1. Class…………………………………………(1mk)
        Reason……………………………………… (1mk)
      2. State the type of evolution that may have led to the emergence of the different beaks shown on the pictures above…………………………………………………(1mk)
      3. Name the type of evolution structure represented by the beaks shown on the pictures above. (1mk)
      4. Observe the pictures carefully. From your observations, what features are responsible for the different types of beaks?………………………………………………………………… (3mks)
    2. Below are pictures from two different animals
      NM2021 Bio PP3 ET2 Q2B
      1. What is the specific function of the two structures shown in the picture (1mk)
      2. Name the class to which each image belongs
        1. X……………………………………………………………………………………………………….. (1mk)
        2. Y………………………………………………………………………………………………………. (1mk)
      3. What type of evolutionary structures is represented in the above pictures (1mk)
      4. Name two economic importance of animal X (2mks)
  3. The photographs below show three bean seedlings that are of the same age but were grown under different environmental conditions.
           NM2021 Bio PP3 ET2 Q3
    1. Based on the external appearance of the seedlings, suggest the condition under which each of them was grown.
      1. Q
      2. R
      3. S
    2. State two observable differences between seedling Rand S
    3. State the term that is used to describe the phenomenon exhibited by specimen S and state its significance. (2mks)
      Term –
      Significance –
    4. Name the response exhibited by seedling Q and explain how it occurs
      Name – (1mk)
      Explanation - (3mks)
    5. State the type of germination that occurs in the three seedlings and give a reason. (2mks)
      Name –
      Reason -

MARKING SCHEME

  1.  
    1.  
      1.  
         Experiment set up    Solution X inside the tubing   Iodine solution outside the tubing
         Beginning of experiment   White/ cream rej.yellow  Yellow/brown colour of iodine retained
         End of experiment  Solution turns blue black/black  No colour change /brown/yellow colour iodine
         remains
      2. Starch
      3. Semi – permeable
      4. 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 the iodine solution.
    2.  
      1. Diffusion/ selective diffusion
      2. Size of diffusing molecules, solubility, thickness of the medium/tubing/membrane/permeability of medium/tubing
  2.  
    1.  
      1. class – Aves
        Reason – presence of beaks and feathers
      2. divergent evolution / adaptive radiation
      3. homologous structures
      4.  
        • length
        • shape
        • size
    2.  
      1. flight
      2. X – Insecta
        Y- mammalian
      3. Analogous structures
      4.  
        • Pollination
        • production of honey used as food
  3.  
    1.  
      1. Q – unidirectional light
      2. R – Sufficient / adequate light
      3. S – in the dark.
    2.  
       Seedling R    Seedling S 
       Short stem   Longer stem 
       Large leaves   Small leaves
       Green leaves   Yellow leaves
       Green stem  Light yellow stem 
       Thick stem   Thinner stem
      Mark first 2
    3. Term – Etiolation
      Significance – the seedling is elongating / growing fast to reach light
    4. Name – positive phototropism; reject phototropism alone
      Explanation – exposure to unidirectional light causes auxins to migrate to the shaded side. This stimulates faster elongation of cells in the shaded side relative to lighted side resulting in faster growth on that side causing the seedling to bend to the light side.
    5. Name – Epigeal
      Reason – cotyledons are brought above the ground

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