Biology Paper 3 (Practical), WASSCE (PC 2ND), 2021

Question 2

 

Diagrams C and D below are illustrations of twoorganisms. Study them and answer questions

2(a) to 2(e).

 

(a) (i)  Identify the organisms in diagram C and D. [2 mark]
(ii) Name the stage of the life cycle of the two organisms as illustrated.[1 mark]
(iii) Name the adult stage of organism C.  [1 mark]

 

(b)(i) State two structural adaptations each of organism C and D to their modes of life.  [8 marks]
(ii) State four observable structural similarities between organism C and D. [4 marks]
(iii) State two observable structural similarities between organism C and D. [2marks]

 

(c) State two ways by which organism C is of economic importance [2 marks]

(d) Name one habitat each of organism C and D.[2 marks]

(e) State three ways by which the population of organism D could be controlled in its habitat.  [3 marks]

Observation

 

Many candidates lost marks for wrongly identifying the stage of the life cycle of the organisms. They also showed poor knowledge of the adaptive features of organisms C and D. Some of them could not also differences of the structural features correspond.

The expected answers are:

(a) (i) Identification of organisms
C:  Caterpillar/Butterfly larva;

D: Mosquito larva/Culex larva   
Note: Do not accept Anopheles larva                                             

            (ii)  Stage of the life cycle of the two organisms illustrated
Larva/Larval stage

(iii)      Adult stage of C
Butterfly

(b)  (i)  Structural adaptation of C and D
                        C:

  • Claspers; for holding firmly onto stems/leaves/branches;
  • Prolegs /true legs for walking /movement;
  • Spiracles; for gaseous exchange;
  • Biting /chewing mouthparts for feeding;                                    
  • It has Osmeterium which emits a foul dour to scare away predator
  • It has simple eyes for vision
  • The waxy cuticle protect the body/ensures conservation of water;
  • Colour for camouflage.                                                                

                        D:

  • Siphon on the last segment; to obtain oxygen/gaseous exchange from the air;
  • Mouth brushes; for feeding;
  • Hairs on segments; for floating/buoyancy;
  • Possesses antennae for sensitivity;
  • Ocellus for sight;
  • Anal gills for gaseous exchange in water/osmoregulation;
  • Feather-like hairs for defence;
  • Its long and cylindrical body enhances its wriggling movement;
  • Horny jaws for feeding/chewing.                                                

(ii) Structural differences between organisms C and D

 


C

D

  • Prolegs/cushion feet present

prolegs/cushion feet absent

  • presence of true legs

absent of true legs

  • presence of claspers

absent of claspers

  • presence of spiracles
  • absence of siphon

absence of spiracles
presence of siphon

  • mouth brushes absent

mouth brushes present

  • absence of hairs on segment

presence of hairs on segment

  • absence of anal gills
  • mandibles present
  • osmeterium present

presence of anal gills
mandibles absent
osmeterium absent

            (iii)       Observable structural similarities between organisms C and D

  • both have segments;
  • both have distinct head;
  • both have three body divisions/head, thorax and abdomen;
  • both have mouthparts;
  • both have simple eyes;
  • both have cylindrical bodies;
  • both have antennae.

(c)        Economic Importance of C

  • it feeds on tender leaves of crops;
  • causes low crop yields;
  • serves as food/feed/edible;
  • some produce silk.

(Habitat of organisms C and D
    C:Leaf/twigs/stems/branches/tree/garden/farm.                                                
D: Pond/gutter/stagnant water/ditches/empty containers/cans with water/puddles.

(e) How to control the population of organism D

  • introduction of tilapia/predators;
  • draining/emptying stagnant water;
  • spraying stagnant water with oil/kerosene
  • spraying stagnant water with insecticides/chemical/larvicides.