Invertebrates Invertebrates are animals without a backbone. 97% of all animals are invertebrates! They are divided into different groups or phyla (plural of phylums). Scientists look at something called symmetry to help classify invertebrates.

Invertebrates Radial symmetry: body parts are arranged around in a circle around a central point (starfish). Bilateral symmetry: have two sides that will match if you draw a line down the center of their body (lobster). Asymetric: these animals have no definite shape at all (sponges).

Click on a box to learn more about that class of invertebrates! When you are done, click the man at the bottom left of the screen to move on! Cnidarian Sponges Arthropods Mollusks Invertebrates Click below when you are done learning about invertebrates: Echinoderms Annelids Flatworms

Cnidarians Have radial symmetry Sometimes they have stinging tentacles around their mouths that they use to catch food. Polyp Jellyfish

Sponges Asymmetric bodies They filter food out of the water as it passes through them.

Roundworms These outnumber every other animal on earth. They can be predators, parasites, or decomposers.

Arthropods Have jointed body parts Bilateral symmetry Segmented bodies Insects, Crustaceans and Arachnids are examples Crustaceans Arachnids Insects Butterfly Beetle House Fly Tarantula Lobster

Flatworms Long, flat bodies Bilateral symmetry Most are parasites that invade other creatures and live off of them. Planaria, tapeworms, liver flukes Planaria Tapeworm Liver Flukes

Annelids Segmented worms Ringed segments Earthworms, leeches Earthworm

Mollusks Soft bodies Protective shell Land mollusks include snails and slugs and have lungs. Water mollusks include oysters, mussels, clams, squids, and octopuses which use gills to breathe. Oyster Snail Octopus

Echinoderms Spiny skin Radial symmetry Thousands of tube-like feet Sea Star, sea urchin, sand dollar, and sea cucumber. Sand Dollar Sea Urchin Sea Cucumber Starfish