BIOLOGY PAPER 3 Marking Scheme - 2017 KITUI MOCK EXAMINATION

Marking Scheme

1.  
   1. Effervescence occurs; (2 marks)
   2. No effervescence; (1 mark)
   3. Enzymes in living potatoes breakdown hydrogen peroxide; to water and oxygen; (4 marks)
   4. The gas produced relights a glowing splint; (1 mark
   5. The gas produced is oxygen; (1 mark
   6.  
       (1 mark
   7. Liver; (1 mark)
   8. Removes toxic substances from the body; (1 mark)
2.  
   1. (7 marks)
      

      Specimen	Steps followed	Identity
      A	1a, 2a, 3a, 4b	Apis mellifera
      B	1a, 2a, 3b	Bedbug
      C	1b, 6b, 7a	Earthworm
      D	1a, 2b, 5b	Scorpion
      E	1b, 6a	Snail
      F	1a, 2a, 3a,4a	Batesian butterfly
      G	1b, 6b, 7b	Leech

   2.  
      1. Arachnida; (1 mark)
      2.  
         • Pairs of legs;
         • Number of body parts;
         • Absence of antennae; Mark first two points
   3.  
      1. Exoskeleton; (1 mark
      2.  
         • Supports and protects inner delicate tissues from mechanical injury
         • Prevents excessive loss of water from body tissues
         •  Prevents desiccation since it is water proof;
         • Provides a surface for muscle attachment; Mark first point
   4.  
      • Helps in pollination;
      • Makes honey which is source of food;

3.  
   1. 
      
      Drawing
      
      • Size and proportion (Same as in Fig 1.1);                1 mark
      • Outline clear and serrate to include petiole;              1 mark
      • Veins shown joined to midrib on either side;             1 mark
      
      Labels
      • Midrib / main vein;                                                 1 mark
      • Petiole;                                                                  1 mark
      • Leaf blade / lamina;                                                1 mark
        Total                                                                      6 marks
   2.  
                  
      1.  
         • Epidermall cell;
         • Guard cell; (Label line must touch only the cell and not stoma)
      2. 2 guard cells ringed; (Reject if more than two guard cells are ringed)
   3.  
      • Prepare a leaf epidermis on a microscope slide;
      • mount under a microscope;
      • count the number of stomata in the field of view;
      • determine the area of the field of view;
      • calculate the area of the leaf surface;
      • number of stomata = area of leaf surface / area of field of view multiplied by number of stomata in the field of view (Maximum = 4 marks)