By: Patty Harris W.L. Swain Elementary Invertebrates By: Patty Harris W.L. Swain Elementary

Two major classifications of the animal kingdom Invertebrates – animals without a backbone. Sponges Cnidarians Worms Mollusks Echinoderms Arthropods Vertebrates – animals with a backbone.

Symmetry Asymmetry – a body plan that can not be divided into mirror images. Radial symmetry – a body plan in which all body parts of an organism are arranged around a central point. Bilateral symmetry – a body plan in which an organism can be divided along only one place to produce two mirror images.

Sponges They are the simplest form of animals. They are filter feeders. They have an asymmetrical body plan.

Cnidarians Soft bodied animals that live in the water. They have radial symmetry. They have stinger cells. Examples: jellyfish, coral, hydra, sea anemone

Worms Three kinds of worms They all have bilateral symmetry. flat worms (tape worms, flukes) round worms (dog heart worms) segmented worms (earth worms) They all have bilateral symmetry.

Mollusks They all have a muscular foot or tentacles. They have bilateral symmetry. Most have shells The squid and octopus are in this group even though they don’t have shells. Examples: squid, octopus, snails, clams

Echinoderms They are bumpy outside. They have radial symmetry. They have many tube feet. Examples: sea stars, sea urchins, sea cucumbers.

Arthropods They have a hard outside skeleton called an exoskeleton. They have bilateral symmetry. They have segmented bodies. They have jointed limbs. Examples: spiders, crabs, insects