The diagrams below illustrate the life cycle of a vector of a tropical disease.  Study the diagrams carefully and use them to answer questions 2(a) and 2(b).

 

 

 

 

 

 

(a)  (i)    Name the stages labelled I to IV.                                                 [2 marks]
     (ii)     Describe two features of each of the labelled stages.                  [8 marks]
    (iii)     What disease is transmitted by the organism?                               [1 mark]

(b)  (i)     List four symptoms of the disease named in 2(a)(iii) above.      [4 marks]
      (ii)     Pouring oil on stagnant water will destroy which              
               labelled stage?                                                                              [1 mark]

 (iii)    List four other methods by which the disease spread by
               the vector can be eradicated.                                                      [4 marks]

OBSERVATION

This question was popular among candidates, majority of the  candidates attempted it and performed fairly well.
In part (a)(ii) candidates were not able to describe features of each of the labelled stages.

The expected answers were as follows:        

     (ii)    Features
         I   Egg     -      Possesses floats/air cells
                         -      Spherical/streamlined in shape.                          

        II   Larva  -      Possession of spiracle which is used for breathing
                         -      Body divided into segment
                         -      Hair float – which help in catching food.      

     III    Pupa    -      Breathing trumpet/tube which touch the surface of water
                -      Free abdomen – the abdomen is free from the body    
                -      Compound eyes, a rounded head and thorax – these developed 
                        more than other stages above
                -      Developing limps – Limbs in a developed stage 
                -     The body parts like rounded head, thorax and a long curved
                       abdomen makes it look like a printed comma.  
                                                                                            
       IV    Imago/Adult mosquito
                           -      Wings for flight
                           -       Possession of proboscis for sucking of blood/nectar
                           -       Possession of antenna
               -       Body divided into three segment.