Page 107 - General and Inorganic Chemistry for Advanced Secondary Schools Students Book Form Five and Six
P. 107
Biology for Secondary Schools
Distinctive features of nematodes
Mouth
The following features differentiate Mouth
nematodes from other animals. Female
Excretory pore genopore
(a) They have a cylindrical, elongated
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and unsegmented body with pointed
ends.
(b) They have special sensory structures Cloaca aperture
known as amphids and phasmids.
Anus
Activity 5.13: Observing external Curved tail Straight tail
features of roundworms
Materials: Preserved specimen of ascaris Figure 5.29: External structure of
(female and male), hand lens, forceps, ascaris (a) male (b) female
notebook, pen and two petri dishes Advantages of nematodes
(a) Nematodes have been used in
Procedure various biological studies. For
1. Use forceps to pick up male and example, some discoveries in the
female specimens of ascaris from field of genetics involved the use
a preserving container and put of nematodes.
them into separate petri dishes. (b) Some nematodes are used as
2. Carefully observe the male and biological control agents to
female ascaris specimens with a control pests, such as locusts
hand lens. and vectors, such as mosquitoes.
3. Describe their external features. Parasitic roundworms attack and
Compare the observed features eat varieties of caterpillars.
with those depicted in Figure (c) Soil nematodes are important
5.29. in recycling of nutrients, hence
contributing to soil fertility.
Question Disadvantages of nematodes
What features distinguish roundworms Task 5.13
from flatworms?
Search from reliable internet sources the
videos or images that show elephantiasis.
Note down what you have observed.
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