Question 1
- List five external similarities of specimen A and specimen B. [5 marks]
- State five external structural differences between specimen A and specimen B.
[5 marks]
- Give five reasons why specimen A is culturable. [5 marks]
Observation
This question was attempted by majority of the candidates and their performance was good. Many candidates however seem not to clearly understand the demand of the Question 1(b) as many could not state the structural differences between Cat fish and Tilapia fish. In Question 1(a) and 1(c) many candidates gave correct answers. Candidates also failed to use correct terminologies such as using ‘Whiskers’ instead ‘Barbels’.
The expected answers are as follows:
(a) External similarities of specimen A (African catfish) and specimen B (Tilapia)
- They are both streamlined in shape/they have streamlined shape
- They both have fins
- They have opercula/they each have operculum
- They both have eyes/pair of eyes
- They both have tails fins/caudal fins
- They both have nostrils
- They both have terminal mouths
- They both have lateral lines
- They both have spiny fins
(b) External structural differences between specimen A (African catfish) and
specimen B (Tilapia)
Specimen A |
Specimen B |
Has barbels |
Has no barbels |
Has cylindrical body shape |
Has bilaterally flattened body shape |
Has no scales |
Has scales |
Has dorsoventrally flattened head |
Bilaterally flattened head |
Has bigger head in relation to the body |
Has smaller head in relation to the body |
Has one continuous lateral line |
Lateral line is broken along the length/discontinuous lateral line |
Has two pairs of nostrils |
Has one pair of nostrils |
Dorsal fin is rayed/soft |
Dorsal fin is spiny |
(c) Reasons why specimen A (African catfish) is culturable
- They can reproduce in captivity/induced spawning
- Can tolerate poor water conditions
- They are hardy
- They can accept artificial feed
- Have high survival rate
- They have resistance to diseases and parasites
- High fecundity/highly prolific/lay many eggs