These animals have tissues organized into organs; the organs are usually organized into systems.
Bodies saclike. Tentacles with stinging cells. Solitary or colonial. Mainly marine. Examples: coral, jellyfish.
The comb jellies. Similar to cnidarians, but with comblike rows of cilia. Marine, solitary. Example: Venus's girdle.
Microscopic wormlike parasites. Have only one organ: a gonad.
The flatworms. Flat, slender bodies. Aquatic, terrestrial, or parasitic. .
The ribbon worms. Flat, slender bodies. Proboscis may extend to several times the length of the body. Mainly marine or terrestrial.
Microscopic marine worms. Hermaphrodites. Have comblike feeding structures.
The rotifers. Head with crown of cilia. A variety of body shapes, ranging from trumpetlike to spherical. Aquatic. Most free-living; some parasitic.
Bodies wormlike, covered with spines; two rows of cilia. Aquatic.
Wormlike; appear segmented because of zonites (rings). Pull themselves along with head spines. Marine.
The roundworms. Slender, cylindrical bodies. Aquatic or terrestrial; mainly freeliving but some parasitic.
The hairworms. Extremely slender bodies. Adults aquatic or terrestrial. Larvae parasitic.
Microscopic; rotifer-like. Retractable spiny heads. Abdomen covered with spiny plates. Marine.
The spiny-headed worms. Bodies flat, with spiny proboscis. Parasitic.
Bodies have tentacled, cupshaped part attached by stalk to rocks, shells, seaweed, or other animals. Usually marine and colonial.
Resemble entoprocts, except that ectoprocts have a coelum, or a body cavity lined with a membrane.
Marine worms with long tentacles. Some are hermaphrodites. Live in hard or leathery tubes formed from secretions. Mostly colonial.
The lamp shells. Soft body parts enclosed in bivalve shells. Most attach themselves firmly to rocks or other substrate.
The mollusks. Body parts usually soft; some enclosed in univalve or bivalve shell. Aquatic or terrestrial. Examples: snail, oyster, octopus.
Burrowing worms covered with spines. Retractable mouth. Marine.
The peanut worms. Burrowing worms with retractable proboscis. Many have tentacles around mouth. Marine.
The spoon worms. Burrowing worms with plump bodies; have proboscis that may extend to several times the body length. Marine.
The segmented worms. Bodies segmented. Aquatic, terrestrial, or parasitic. Examples: earthworm, leech.
The water bears. Microscopic. Have four pairs of stumpy legs. Most live in water around mosses or lichens.
The tongue worms. Flat body with four claws. Parasites in lungs and nasal passages.
The velvet worms. Body with 14 to 43 pairs of clawed legs. Terrestrial.
The arthropods. Largest animal phylum. Segmented bodies with external skeletons and jointed appendages. Aquatic, terrestrial, or parasitic. Examples: insects, spiders, millipedes, lobsters.
The beard worms. Live on sea floor in hard, upright tubes formed from secretions. Long tentacles at front of body.
The arrowworms. Transparent, torpedo-shaped bodies. Marine.
The echinoderms. Internal skeleton of calcite crystal plates. Unique circulatory system. Aquatic, mainly marine. Examples: sea urchin, starfish.
The hemichordates. Soft-bodied; have gill-slits and proboscis. Marine, some kinds burrowing in sea bottoms. Solitary or in colonies. Example: acorn worm.
The chordates. Large, varied phylum. Have nerve cord; most have bony internal skeleton. Aquatic or terrestrial. Examples: amphioxus, bird, fish, humans.