Question 1
(a) Give four reasons why a spider is not considered an insect?. [4 marks]
(b) (i) State five structural differences between a prawn and a cockroach. [5 marks]
(ii) State three structural similarities between a prawn and a cockroach. [3 marks]
(c) State three structural features that adapt the lizard to life on land. [8 marks]
Observation
Many candidates attempted this question and the performance was average because many candidates just wrote the features of spiders without relating it to the reason they are not insects. Some candidates wrote that spiders have four pairs of legs only.as the answer.
Some candidates were able to state the differences between a prawn and a cockroach but some candidates did not correspond the answers to score marks
Some candidates were able to state some similarities between a prawn a cockroach.
Also, the characteristic features that adapt the lizard to terrestrial life was not adequately answered because some candidates did not relate the structural features with the functions of the features.
The expected answers are:
(a) Reasons a spider is not considered an insect
- It has four pair of legs while insects have 3 pairs of legs;
- It has two body division/cephalothorax and abdomen/opisthosoma while insects have 3 body divisions, head, thorax and abdomen;
- It has pedipalp while insects have antennae;
- It has no wings while some insects have wings;
- It has eight simple eyes while insects have two compound eyes;
- It has spinnerets while insects do not have;
- It has chelicerae while insects do not have;
- It respires by means of lung book while insects respire with trachea.
(b) (i)Structural differences between a prawn and a cockroach
Prawn |
Cockroach |
|
three body divisions/head, thorax and |
|
one pair of antenna; |
|
two pair of wings; |
|
three pairs of walking legs; |
|
presence of spiracle/trachea; |
|
absence of stalked compound eyes; |
|
absence of swimmerets |
|
absence of rostrum |
|
absence of pincers/chelicera |
|
absence of carapace |
Note: Points must correspond to score.
(ii) Structural similarities between a prawn and a cockroach
- Jointed appendages;
- Bilateral symmetry;
- Exoskeleton made up of chitin;
- Metameric segmentation.
(c) Characteristic features that adapt the lizard to life on land
- dry scaly skin; to protect it from drying up;
- clawed digits;for climbing /holding on to support;
- leathery shelled eggs; to protect embryo from mechanical damages/ microbial infections/desiccation;
- respiration; lungs for respiration;
- limbs; for movement on land;
- well-developed tongue which can be protruded and retracted; for feeding/sensing the environment.