Candidates generally performed well in this question as many could identify species
   B as the producer with correct reasons.  Some candidates could not identify the roles
   of each species in the habitat.

   Many candidates scored for the shape of the pyramid but missed the arrangement of
   the pyramid of numbers and biomass.   Candidates could not give examples of the  
   organisms that would likely  constitute A,B,C and D, if the habitat was a marine or a
   rainforest habitat; and many candidates could not specify the organisms that represent    
   A ,B ,C or D.  Most candidates did quite well in explaining the effect on D if  the  
   population of  A decreases, but could not give enough points and so did not
   score full marks.

 

 

                 Expected answers are:

                 Roles of each species

     (b)     A  -  herbivore/;feeds on B/primary consumer;  and passes on the
                                 energy to C                                                    

                         B  -   Producer; manufactures food (by trapping solar energy); which is
                                  passed on to herbivores/primary consumer.    
                        C  -    Carnivore/;feeds on A ; and passes its energy to D/tertiary
                                  Consumer.                                                               

                         D  -   Carnivore/feeds on C/tertiary consumer                       

                                    No of organisms

                                                                   
                                                                                                                                                   35
                                                                         150
                                                                       1500
                                                                        6000

(i)      Pyramid of numbers

                                                                 
                                                                                                                                                   10kg
                                                                          50kg
                                                                          500kg
                                                                                                                                               1500kg

 

                    (ii)       Pyramid of biomass

                  Correct shape  (CS)             
                  Correct arrangement (CA)    

                (d)          (i)   Marine

                       A  -      Zooplankton, fish fingerlings, copepods, crayfish/shrimps, 
                                   whale/any other correctly named  marine herbivore       
            
               B   -    Phytoplankton, Diatoms, Algae/Sea weeds/any other correctly   
                        named  marine plant                                                              
                                                                                                        
               C  -   Tilapia, Dogfish, Rayfish/Trigon, Herring/any other correctly named 
                       marine secondary consumer                                                           

               D  -    Shark, Kingfisher/Pelican, Dolphins, Whale/any other correctly  
                       named marine tertiary consumer.
                                                   

                      (ii)    Rain Forest

             A -        Insects, Earthworms, Snails, Tortoise, Monkeys/Baboons,   
                       Rodents/Grasscutter/Rabbit, Birds, Antelope/any other correctly                
                       named herbivore                                                                                

           B  -    Mahogany, Chlorophora sp, Palm tree, Ceiba, Ferns,                               
           Bamboo/Trees/Shrubs/Grass/Herb                                                    

           C  -       Pangolin/Ant-eater, Lizards, Snakes/Toad/Trog/any other correctly 
            named secondary consumer                                                           

                      D  -     Hawk, Kite, Owl, Python/ any other correctly named tertiary
            consumer                                                                                              
                   
     (e)   Decrease in the population of A will lead to decrease in C; which will lead to a
            decrease in D; as a result of scarcity of food; many of D will die off/migrate
         .