DETAILED COMMENTS ON EACH QUESTION
Question 4
. The diagrams below illustrate parasites of farm animals. Study them and answer the questions that follow.
- Identify the parasites labelled I and II.
- Mention three external features of the parasite labelled I.
- Name the part of the body of the host where the parasite labelled II is found.
(1 mark)
- State four adaptive features of the parasite labelled II on its host.
- List two intermediate hosts of the parasite labelled II.
(4 mark)
(2mark)
- State three effects of the parasite labelled I on its host.
(2 mark)
(3 mark)
(3 mark)
Observation
- Many candidates could identify the tapeworm but were unable to identify the louse.
- Candidates were not specific in naming the part of the host where the tapeworm is found.
- However, many candidates were able to state the adaptive features of tapeworm on its host.
Many candidates wrote ‘intestine’ instead of the ‘small intestine’.
The expected answers include:
- Identification of the Parasites
- External features of the parasite labelled I (Louse)
- Part of the body of the host where the parasite labelled II (Tapeworm) is found
-
- Adaptive features of the parasite labelled II (Tapeworm) on its host).
- Intermediate hosts of the parasite labelled II (Tapeworm),
-Cattle
- Pigs
- Possesses four suckers with which it attaches itself to the walls of the intestine of its host
- Possesses two rows of hooks with which it fixes itself into the intestine for a firm grip
- The whole body is covered with cuticle which prevents it from being digested by the digestive enzymes of its host
- Has the ability to absorb products of digestion with its entire body since it has
no digestive system of its own
-Its excessive length increases surface area for absorption
- Produces many proglottides full of eggs
- Rostellum forms part of appendages for attachment
- Effects of the parasite labelled I (Louse) on its host
I -Louse
II -Tapeworm (Taenia solium)
- Head
- Thorax
- Three pairs/six legs with sharp claws
- Segmented abdomen
- A pair of antennae
- A pair of compound eyes
- Mouthparts for biting and sucking
- Small intestine
- The host becomes restless due to skin irritation
- Loss of appetite n
- Loss of weight n
- Reduction in livestock productionn
-Causes loss of hairs or feathersn
-Injuries caused may serve as source of secondary infectionn
-It sucks blood of host leading to anaemian
-eventually leads to death