Invertebrates- Animals lacking a backbone.

1. Annelids

1.1. Annelids are bilaterally symmetrical animals and are usually just a few millimeters in size.

1.2. Some annelids are deterivores and some of them are blood suckers.

1.3. They sometimes live in water and sometimes live on the land in soil or aquatic settings.

2. Crustaceans

2.1. They have a hard outer shell. These include crabs, lobsters, crayfish, and krill.

2.2. Crustaceans are scavengers. They mostly feed on dead creatures.

2.3. Most all crustaceans live in the water. Most of them live in the ocean, however there are some that live in fresh water.

3. Mollusks

3.1. They all have a head, a foot and a visceral mass. The head is where the brain is stored. The visceral mass holds the internal organs. These include clams, snails, muscles, squids and octopods.

3.2. Usually mollusks have a shell.

3.3. Land mollusks will eat things like plants and vegetables. Mollusks of the sea will eat things like plankton and small krill.

4. Echinoderms

4.1. Echinoderms have no brain, heart, or eyes.

4.2. They are characterized by having radical symmetry and 5 or more arms.

4.3. Examples are starfish, sea urchins, sand dollars, and sea lillies

4.4. Some eat mollusks. Others eat drifting particles in the water.

5. Arachnids

5.1. All arachnids have eight legs. These include spiders, scorpions, and mites.

5.2. They are mainly carnivores and will eat insects. For example a spider will trap a fly in its web and then later eat it.

5.3. They live many different places. They may live in a caves where it is dark and cool. And some of them live close to water.