Animals part 1
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Created by:
Amberholloway on November 17, 2011
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25 terms
Terms | Definitions |
|---|---|
 acoelomate | an animal that lacks a coelom, or body cavity |
| anus | opening through which wastes leave the digestive tract |
| asymmetry | not identical on either side of a central line; not symmetrical |
| bilateral symmetry | body plan in which only a single, imaginary line can divide the body into two equal halves; characteristic of worms, arthropods, and chordates |
| blastula | hollow ball of cells formed when a zygote undergoes a series of divisions |
| cephalization | concentration of sense organs and nerve cells at the front of an animal's body |
| closed circulatory system | system in which blood is contained within a network of blood vessels |
| coelom | fluid-filled body cavity lined with mesoderm |
| deuterostome | animal whose anus is formed from the blastopore of a blastula |
| ectoderm | Outermost germ layer of most animals; gives rise to outer layer of the skin, sense organs, and nerves |
| endoderm | innermost germ layer of most animals; develops into the linings of the digestive tract and much of the respiratory system |
| external fertilization | process in which eggs are fertilized outside the female's body |
| gastrovascular cavity | digestive chamber with a single opening, in which cnidarians, flatworms, and echinoderms digest food |
| hermaphrodite | individual that has both male and female reproductive organs |
| hydrostatic skeleton | layers of circular and longitudinal muscles, together with the water in the gastrovascular cavity, that enable movement |
| internal fertilization | Process in which eggs are fertilized inside the female's body |
| invertebrates | Animals that do not have a backbone, or vertebral column. |
| medusa | motile stage of the life cycle of a cnidarian that has a bell-shaped body |
| mesoderm | middle germ layer of most animals; gives rise to muscles and much of the circulatory, reproductive, and excretory systems |
| open circulatory system | system in which blood is not always contained within a network of blood vessels |
| polyp | usually sessile stage of the life cycle of a cnidarian that has a cylindrical body with armlike tentacles |
| protostome | Animal whose mouth is formed from its blastopore |
| pseudocoelom | body cavity between the endoderm and mesoderm tissues that is partially lined with mesoderm tissue |
| radial symmetry | body plan in which body parts repeat around the center of the body; characteristic of sea anemones and sea stars |
| testes | organ that produces sperm |
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