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 absent |
|
absent of true legs |
|
absent of claspers |
|
absence of spiracles |
|
mouth brushes present |
|
presence of hairs on segment |
|
presence of anal gills |
(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.