Phylum Annelids
Annelids are worms, with bodies made up of ring-like segments. Most of them live in water, though some, like the earthworm, live in moist soil. Characteristics: l animals with bodies made up of ring-like segments. earthworm position of mouth
Nematodes are worms, but unlike annelids their bodies are not divided into segments. They are usually white, long and thin. They live in many different habitats. Many nematodes live in the soil. Characteristics: l animals with long, thin, unsegmented bodies.
segmented body
clitellum
Phylum Nematodes
nematode
position of anus Figure 1.7 Classifi
cation
of
annelids.
Figure 1.9 Classifi
cation
of
nematodes.
Phylum Molluscs
Molluscs are soft-bodied animals, sometimes with a shell – for example, snails; or without – for example, slugs. Characteristics: l animals with soft, unsegmented bodies l may have a shell. snail
Activity 1.1 Making
biological
drawings skills
C2 Observing, measuring and recording
coiled shell eye
Biologists need to be able to look closely at specimens – which might be whole organisms, or just part of an organism – and note significant features of them. It is also important to be able to make simple drawings to record these features. You don’t have be good at art to be good at biological drawings. A biological drawing needs to be simple but clear.
soft, unsegmented body squid
eye
You will be provided with a specimen of an animal to draw.
soft, unsegmented body with internal shell
Figure 1.8 Classifi
cation
of
molluscs.
(... continued on page 8) Chapter 1 Classifi
cation 7