Invertebrates - Animals without Backbones

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Invertebrates outnumber vertebrates in diversity and number.

Arthropods, one of eight major groups of invertebrates, make up the largest group of animals. There may be as many as 10 million kinds of arthropods. All arthropods share three common characteristics:

1. their bodies are divided into segments, or parts
2. they have jointed legs, and
3. they have hard outer coverings called exoskeletons.

Arthropods also have well-developed sensory organs and unique mouthparts.

Arthropods are divided into four main groups:

• Diplopods and Chilopods - This group includes millipedes and centipedes. Both animals look somewhat like worms with many legs. Millipedes are harmless plant-eaters, while centipedes are carnivores, injecting poison into their victims.
• Crustaceans - This group's members have five pairs of legs and two main body parts, and they usually live in water. Some examples of crustaceans are shrimp, lobsters, and crabs.
• Arachnids - Members in this group have two main body parts and four pairs of legs. Spiders, ticks, and mites make up this group.
• Insects - This group makes up the largest group of arthropods. Insects have three pairs of legs and a body divided into three parts. The three body parts include the head, the abdomen, and the thorax. Wings and legs are joined to the thorax. Insects also have two antennae, which help them smell, feel, and sometimes taste and hear.

Label the Millipede

More on Millipedes

An Array of Arthropods (handout)

Arthropod Arithmetic (handout)

Insect Intellect (handout)

Resource links:
http://www.enchantedlearning.com/subjects/invertebrates/index.shtml

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