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acoelomate
| triploblastic animals without a cavity between the digestive tract and outer body wall |
anterior
| The head of a bilaterally symmetrical animal |
Archenteron
| The endoderm-lined cavity, formed during the gastrulation process, that develops into the digestive tract of an animal. |
Bilateral Symmetry
| A body form in which only one longitudinal cut through the organism's center results in identical halves |
blastopore
| single opening in gastrula, opening to the outside from archenteron |
cephalization
| having sensory equipment concentrated at the anterior end, along with a central nervous system in the head |
cleavage
| (embryology) the repeated division of a fertilized ovum |
Coelom
| A body cavity that contains an animal's internal organs |
coelomate
| an animal that has a body cavity in which the internal organs are located |
determinate cleavage
| A type of embryonic development in protostomes that rigidly casts the developmental fate of each embryonic cell very early |
diploblastic
| having 2 germ layers |
dorsal
| Pertaining to the back of a bilaterally symmetrical animal |
ectoderm
| the outer germ layer that develops into skin and nervous tissue |
endoderm
| the inner germ layer that develops into the lining of the digestive and respiratory systems |
enterocoelous
| development of body cavities by budding of mesoderm from the wall of the archenteron |
gastrula
| second phase of early embryonic development that results in formation of blastopore |
germ layers
| Three main layers of an animal |
indeterminate cleavage
| a type of embryonic development in deuterostomes in which each cell produced by early cleavage divisions retains the capacity to develop into a complete embryo |
larva
| the immature form of an animal that looks very different from the adult. |
lophophore
| horseshoe-shaped or circular crown of ciliated tentacles that surround the mouth |
mesoderm
| the middle germ layer that develops into muscle and bone and cartilage and blood and connective tissue |
metamorphosis
| the marked and rapid transformation of a larva into an adult that occurs in some animals |
parazoa
| an organism without tissue layers |
posterior
| Pertaining to the rear, or tail, of a bilaterally symmetrical animal |
protostome
| characterized by spiral, determinate cleavage, schizocoelous formation of the coelom, and development of the mouth from the blastopore. |
Pseudocoelom
| A body cavity that is not completely lined by tissue derived from mesoderm |
radial symmetry
| the quality of having many lines of symmetry that all pass through a central point. |
Schizocoelous
| In protosomes, a pattern of development in which a solid mass of mesoderm cells splits to form the cavity that becomes the coelom. |
triploblastic
| has three germ layers: the ectoderm, endoderm, and mesoderm. |
ventral
| Pertaining to the underside, or bottom, of a bilaterally symmetrical animal |
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