Unit 3 INVERTEBRATES

INVERTEBRATES Are animals which do not have a skeleton Size Most are very small, some such as giant squids Body shape Most invertebrates are symmetrical but some have irregular bodies. Body covering Many bodies are protectec by shells or exoskeletons In the sea In fresh water On land The invertebrates live Can move Attach themselves to rocks or the sea floor Parasites: Live inside other animals Are oviparous Invertebrates

INVERTEBRATES GROUPS Sponges Have irregular bodies. They cannot move Cnidarians Have jelly-like bodies. They have tentacles which can sting you. Worms Have long, sofl bodies. Some are cylindrical, and others flat. Many are parasites. Echinoderms Are symmetrical. They have a skeleton made up of hard plates. Arthropods Are covered by a hard exoskeleton. Some are aquatic. Molluscs Have a soft body. Many are covered by one or two shells

ARTHROPODS Arthropods have an external exoskeleton Made up of many small plates The exoskeleton is rigid. From time to time the Arthropods sheds it ,and grows a new ,flexible one. As a result arthropods grow ARTHROPODS GROUPS INSECTS Insects body is divided in three parts.the thorax has six legs ARACHNIDS Have eight legs . Body divided in abdomen and cephalothorax CRUSTACEANS Have ten or more legs . Body divided in abdomen and cephalothorax MYRIAPODS Have long bodies with many legs. The head has one pair of short antennae.