An invertebrate is an animal without a backbone. They have no internal skeleton and normally have soft, flexible bodies. Some have a hard outer skeleton (an exoskeleton) which protects them. Here are seven of the main categories: Insects Crustaceans Echinoderms (bees, ladybirds, ants) (crabs, shrimps, lobster) (starfish, sea urchin) Insects have a hard outer casing which Crustaceans have a hard outer shell which Echinoderms only live in water and protects the soft body inside. The body of protects the soft inner body. The body is made have a hard spiny covering or skin. an insect is split into three sections: up of two parts which sometimes look like Their bodies also have radial head, thorax and abdomen. they are fused together. symmetry with five or more arms or legs. Insects have antennae and usually have 3 Crustaceans have more than 3 pairs of legs pairs of legs. They also sometimes and many will have claws at the end of the An echinoderm can grow back part have wings. first set of legs. of its body if it becomes damaged. Annelids Arachnids Molluscs Protozoa (earthworms, leeches) (spiders, scorpions) (clams, octopus, snails, slugs) Protozoa are tiny, tiny An annelid has no legs and All arachnids have eight legs and Molluscs have soft bodies which animals that we cannot no hard outer skeleton. they do not have antennae. are not segmented. see without the help of a The body of an annelid is Their bodies are made up of two microscope. They live divided into many little parts – the cephalothorax Most molluscs live on water but everywhere – on land, in segments – like rings (where the head is found) and the some live on land. water and also on other joined together. abdomen. animals or plants. Some molluscs have their own Annelids can have bristles They also have a tough shell which they can use for on their bodies. exoskeleton. protection. In your books, draw a table like the one below. Sort the invertebrates into the correct categories. Insect honey bee octopus crab Crustacean earthworm mussels grasshopper Echinoderm Annelid starfish squid prawn Arachnid black widow snail scorpion Mollusc lobster sea urchin leech.