Biology Paper 3 Form 3 Questions and Answers - End Term 2 Exams 2021

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Biology Paper 3 Form 3 End Term 2 Exams 2021 with Marking Schemes

Answer all the questions in the spaces provided.

  1. You are provided with chemical reagents Q (Iodine solution), R (NaOH), S (CuSO4), T (DCPIP)and food solution X 
    Using the reagents provided carry out food test on solution X
    1. Record your results in the table below. (12marks)
       Food Substance  Procedure  Observation  Conclusion
    2. Suggest the importance of food substance present in solution X in a human body. (2mks)
  2. Below is a photograph of a certain animal. Examine it and answer the questions that follow.
    1. Giving a reason in each case, classify the animal into the taxonomic units in the table below. (4 marks)
       Taxonomic unit  Name of taxonomic unit  Feature
    2. Study the photograph shown below part of animal above.
      List adaptive characteristics of part labeled G to its function. (4mks)
    3. The following illustration shows a flow in the photograph shown above.
      1. Indicate on the illustration the direction of blood and water flow. (1mk)
      2. Name the type of flow represented in the illustration (1mk)
      1. Name the process by which oxygen leaves water into capillaries of filaments. (1mk)
      2. What condition enables an efficient exchange of oxygen by process identified in d(i) above. (1mk)
    5. The atmospheric air has more oxygen than that dissolved in water yet a fish dies immediately after being withdrawn from water. Explain. (1mk)
  3. Study the photographs of plant structures shown below then answer the questions.
    1. For each type of structure shown above state a dispersal agent (4marks)
       Structure  Dispersal agent
    2. Name the observable adaptive features in X1 and X2 that enable them to be dispersed by the dispersal agent identified. (2marks)
       Structure Adaptive features
      1. Give possible description of leaves and roots of plant of flower labeled R2.
        Leaves ……………………………………………………………………..(3mks)
      2. Flower R2 has polypetalous characteristic. Explain. (1mk)
      3. Name part labeled Q on X3. (1mk)

 Marking Scheme

    1. (12marks)

      Food substance





      Add 3 drops of iodine solution

      Solution turns blue black

      Starch present


      Add drops of NaOH

      Add drops of CuSO4

      Solution turns purple

      Protein present

      Ascorbic acid/ Vitamin C

      Into about 2cm3 of DCPIP add drops of food solution X

      Blue colour of DCPIP persists

      Ascorbic acid absent

    2. – body building food
      - Energy giving food
    1. Giving a reason in each case, classify the animal into the taxonomic units in the table below.                      (4 marks)
       Taxonomic unit  Name of taxonomic unit  Feature
       Phylum  Chordata  Presence of a notochord at a stage of embryo development
       Class  Pisces  Presence of fins; presence of lateral line;
       Presence of gills
      1. Have moist surfaces to dissolve oxygen gas
      2. Have a thin epithelial lining for gases to move through a short distance
      3. Have a large capillary network for maximum gaseous exchange
      1. answer on figure    
      2. Counter current flow.
      1. Diffusion.
      2. A steep concentration gradient of oxygen gas.
    5. While in water filaments part and creates a large surface area for gaseous exchange.
      When a fish is removed out of water into air, filaments sticks together reduces surface area for gaseous exchange fish suffocates and dies.
       Structure  Dispersal agent
       X1  Wind
       X2  Water
       X3  Explosive mechanism
       X4  Animal
       Structure Adaptive features
       X1  Has wing like structures that enable it to float in wind
       X2  Mesocarp fibrous and spongy to trap air;
       Air trapped make fruit light and buoyant to float on water.
      1. Root system of R- Tap root; star shaped xylem vessel
         Leaf characteristics of R2 – Network venation; presence of petiole;
      2. Polypetalous characteristic; petals are free/petals are not fused
      3. Funicle
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