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

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Invertebrates are animals without backbones.

There are three (3) groups of invertebrates:

  1. Annelids
  2. Molluscs
  3. Arthropods

Annelids

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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

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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

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Arthropods can be further sub-divided into four groups:

  1. Insects
  2. Arachnids
  3. Crustaceans
  4. Myriapods

A grasshopper

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A dragonfly has three pairs (six) legs

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Insects

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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

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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

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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

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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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Ready for the next module?

In the next module, we will look at the classification of microorganisms.

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