In this module, you will learn:
- invertebrates are animals without a backbone
- the three main groups of invertebrates
Resources to help you:
- Textbook: page 44
- Notebook: page 23, 24 and 25
A snail on a tree stump
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Invertebrates
Invertebrates are animals without backbones.
There are three (3) groups of invertebrates:
- Annelids
- Molluscs
- Arthropods
Annelids
Below are some of the characteristics of annelids:
- they have long cylindrical bodies
- they are divided into many segments
- each of the segments have many bristles
A blood worm
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Movement of an annelid
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A snail is a mollusc with a shell
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Octopuses are also under the class of mollusc
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Molluscs
Below are some of the characteristics of molluscs:
- they have soft bodies that may be covered by a shell
- they have a muscular foot for movement
- they have tentacles
A slug is a mollusc that does not have a shell
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Arthropods
Arthropods can be further sub-divided into four groups:
- Insects
- Arachnids
- Crustaceans
- Myriapods
A grasshopper
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A dragonfly has three pairs (six) legs
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Insects
Below are some of the characteristics of insects:
- they have one pair of antenna
- they have three pairs or six legs
- they have compound eyes
The bee is an insect that is important in pollination
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Arachnids
Below are some of the characteristics of arachnids:
- they do not have antenna
- they have four pairs or eight legs
- they have simple eyes
A scorpion in the desert
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A tarantula is a spider with four pairs of legs
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A Sally lightfoot crab
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A shrimp under the sea
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Crustaceans
Below are some of the characteristics of crustaceans:
- they have two pairs of antenna
- most have gills and live mainly in water
- they have compound eyes
A lobster
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Myriapods
Below are some of the characteristics of myriapods:
- they have one pair of antenna
- they have simple eyes
- they have many legs
A centipede has many legs
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A millipede moving across the ground
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