| A | B |
|---|
| invertebrate | an animal that does not have a backbone |
| ectoderm | outer tissue layer of a developing animal |
| endoderm | inner tissue layer of a developing animal |
| mesoderm | middle tissue layer of more complex developing animals |
| phylum | a large classification grouping of many different species that have major traits in common |
| tissue | group of similar cells that work together to perform a specific function |
| sponge | the simplest invertebrate |
| central cavity | the hollow center of a sponge |
| pores | small openings on a sponge that connect with the central cavity |
| flagellum | whip-like structure on a cell used for movement |
| budding | type of asexual reproduction used by the sponge |
| regeneration | the regrowth of body parts that have been lost or damaged |
| coelenterate | invertebrate that has a central body cavity with a single opening |
| tentacles | armlike extensions used to catch food |
| hydra | one of the few freshwater coelentrates |
| tubelike and umbrella shaped | two body forms of coelentrates |
| flatworm | invertebrate with a flattened body (simplest of all worms) |
| organs | two or more different tissues that work together to perform a function |
| parasite | organism that lives on or in another organism and harms it |
| pharynx | a tube in some worms that join the mouth with the rest of the digestive system |
| flukes | flatworm parasites that live in the liver or blood of certain animals |
| tapeworms | flatworm parasites found in the intestines of vertebrates such as humans and cattle |
| roundworm | a smooth, cylinder-shaped worm with pointed ends and a tubelike digestive system |
| anus | an opening at the end of the digestive tract |
| trichina | roundworm parasites found in the muscles of pigs |
| segmented worm | a worm whose body is made up of ringlike sections or segments |
| setae | short bristles that help an earthworm move |
| crop | chamber that stores food |
| gizzard | chamber in which food is ground into small particles |
| mollusks | an animal that has a soft body usually covered by a hard shell |
| foot | muscular structure used by mollusks for movement |
| mantle | fleshy tissue that covers and protects the organs of a mollusk |
| bivalve | a mollusk having two shells hinged together |
| univalve | a mollusk that is usually covered by a single shell |
