Invertebrates Sponges Anemone and Coral Jellyfish Comb Jellies Annelids Roundworms Bivalves Gastropods Octopi and Squid Starfish and Urchins Insects Crustaceans Spiders and Scorpions Examples: Anthozoa Arachnida Asteroidea Bivalvia Cephalopoda Cirripedia Cnidaria Coleoptera Decapoda Diplopoda Echinoidea Insecta Isopoda Haliotidae Polyplacophora Polychaeta Scyphozoa Search Biology4Kids

There are two basic groups of higher animals. You've got your vertebrates and your INVERTEBRATES. While both have become quite advanced through the process of evolution, there is one fundamental difference. Invertebrates do not have backbones. Both groups are in the Kingdom Animalia, but their bodies are organized differently. WHAT'S GOING ON? All invertebrates share common traits. At the bottom of the invertebrate world are the sponges. Sometimes they don't fit in but they are still part of the group. Here's a nice and neat little list... 1 - They are multicellular. It's more than being a colony of individual cells; these cells are working together for the survival of the organism. Cells have specific duties and responsibilities. 2 - No backbone. We already talked about this one. That's the whole definition of invertebrate... No vertebrae. 3 - No cell walls. When we talked about plants we always mentioned cell walls. Invertebrates don't have them. Remember that even if they all don't look like animals, they are. Being an animal means no cell wall. 4 - Here are a few that have the qualifier "most" attached. That means not all of them have the trait, but most do. Most of them have tissues (not sponges) that are specific organizations of cells. Most of them reproduce sexually (not asexually). That means two gametes combine to form a new organism. Those gametes come from separate organisms (male and female). Most can move. Even sponges move when they are very young and very small. Once they settle down they don't move anymore. Other invertebrates like lobsters and insects move around their whole lives. Most invertebrates are organized in a way called SYMMETRICAL. That's when there is a line you can draw down the middle of the organism. Both sides look like mirror images. Draw a line down the middle of yourself and one side looks like the other side. If you draw a line down the middle of an octopus you would find two sides with equal parts. Remember we said most? Sponges and some coral are not symmetrical. 5 - They can't make their own food. Scientists use the word HETEROTROPH. Heterotrophs feed off of other things to get their energy. Plants are AUTOTROPHS (they make their own food). Being a heterotroph is one of the main characteristics of being an animal. We eat things, whether it is plants or other animals. That's just they way the world works.

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