INVERTEBRATE ANIMALS

• MOST ANIMALS ARE INVERTEBRATES• CNIDARIANS & WORMS HAVE DIFFERENT

BODY PLANS• MOST MOLLUSKS HAVE SHELLS, &

ECHINODERMS HAVE SPINY SKELETONS• ARTHROPODS HAVE EXOSKELETONS &

JOINTS

Most Animals are Invertebrates• Invertebrates: animals with no backbone or bone tissue.

Some live in water, desserts and even inside of other organisms.• Most are small (crickets,oyster,sea star, earthworm, spider).

Giant squid though can be about 60 feet long and weigh 1000lb. SIX GROUPS OF INVERTEBRATES:Sponges (simplest, live in water & filter food out of water); Cnidarians (live in water, central opening surrounded by tentacles); Worms (soft, tube shaped body); Mollusks (muscular foot to move or get food); Echinoderms (central opening to take in food); Arthropods (found on land, water & air, have legs, maybe wings)

SPONGES: Simplest Animals• Sponges are simplest multicellular animals; • are sessile (live in 1 spot & don’t move); • have no tissue or organs just collection of cells; • feed constantly by filtering out plankton/small

organisms in water surrounding them.• Sponge pore cells are on body wall leading into

larger canals with other cells. Specialized cells filter out food particles & oxygen. Other cells digest food. Some cells have spicules (spines with calcium to make body hard & give support)

SPONGES• Can reproduce asexually

by buds breaking off & floating away, landing & growing.

• Sexually release sperm in water to either meet eggs in other sponges, or sometimes eggs floating in water. Fertilized egg forms free swimming larva, that will land, become sessile again & grow into adult sponge.