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THE ANIMAL KINGDOM The animal kingdom can be divided into 9 smaller groups. Each group is called a phylum. PHYLUM PORIFERA Sponges Sponges are sessile animals (they spend their lives attached to rocks) Water enters the small pores of a sponge, travels through canals, and exits through a large hole at the top of the sponge. PHYLUM CNIDARIA Jellyfish, sea anemones, corals Members of this phylum have tentacles with stinging cells. Cnidarians can have one of two body shapes: an umbrella-shaped medusa form, like the jellyfish on the left, or a vase-shaped polyp form, like the sea anemone on the right. Coral reefs contain many members of Phylum Cnidaria. PHYLUM PLATYHELMINTHES Flatworms The worms in this phylum are all very thin and flat, like this parasitic liver fluke. All flatworms, including this planarian, have bilateral symmetry. Flatworms are the first animals to have a head. Note the hooks and suckers on the head of this tapeworm. PHYLUM NEMATODA Roundworms Nematodes are not segmented; their body surfaces appear smooth. Many nematodes are parasites, such as this pork worm named Trichinella. Nematodes have a complete digestive tract, with a mouth at one end where food enters, and an opening at the other end where wastes exit. PHYLUM MOLLUSCA Clams, snails, squid, octopus Most mollusks have a hard shell covering their soft bodies. Clams have a wedge-shaped muscular foot used for locomotion. Mollusks breathe by means of gills. Not all mollusks have shells. This squid does not. This octopus does not have a shell either, but it is still a mollusk. PHYLUM ANNELIDA Earthworms, sandworms, leeches Annelids have bodies that are segmented (divided into sections). Annelids have a circulatory system to pump blood. This earthworm has 5 hearts! Annelid worms have a body cavity called a coelom which provides room for organ development. PHYLUM ARTHROPODA Crayfish, lobsters, crabs, insects, spiders All arthropods, including this tick, have jointed legs. Arthropods have a crunchy shell called an exoskeleton. Arthropods have very well-developed sense organs. PHYLUM ECHINODERMATA Starfish, sand dollars, sea urchins Echinoderms have spiny (prickly) skin. Adult echinoderms have radial symmetry. The bottom of this starfish is covered with tube feet for locomotion. PHYLUM CHORDATA Fish, amphibians, reptiles, birds, mammals Members of Phylum Chordata have a backbone (they are vertebrates). Phylum Chordata can be subdivided into 7 classes: AGNATHA CHONDRICHTHYES OSTEICHTHYES AMPHIBIA REPTILIA AVES MAMMALIA Class Agnatha includes jawless fish such as lampreys. They are parasites on other fish. Class Chondrichthyes includes fish whose skeletons are made of cartilage, such as sharks, rays, and skates. Class Osteichthyes includes fish whose skeletons are made of bone. Class Amphibia includes semi-aquatic animals with moist skin. They must return to the water to breed. Class Reptilia includes snakes, lizards, turtles, crocodiles, and iguanas. They have dry, scaly skin. Members of Class Aves have wings and feathers for flight. Class Mammalia includes animals with hair or fur. Females have mammary glands to nurse their young with milk.
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