Zoology

Parazoa

Animals without true tissues, exemplified by sponges

Eumetazoa

Clade of animals possessing true tissues

Clade

Evolutionary branch including a single ancestor and all its descendants

Porifera Symmetry

Asymmetric or lacking symmetry

Cnidaria Symmetry

Radially symmetrical

Platyhelminthes Symmetry

Exhibiting bilateral symmetry

Ectoderm

Outer germ layer in embryonic development

Endoderm

Inner germ layer in embryonic development

Mesoderm

Middle germ layer in embryonic development

Spicule

Unique feature of Porifera, aiding in structure and defense

Cnidocyte

Unique to Cnidaria, specialized stinging cells

Gastrovascular Cavity

Found in Eumetazoa, functions in digestion and circulation

Protostome

Mouth develops first in embryonic development

Coelom

Body cavity surrounding the gastrointestinal tract

Cephalization

Concentration of sense organs and nerve cells at the front of an animal's body

Nerve Net

Spread of neurons throughout the body, opposite of cephalization

Metamerism

Segmentation of the body

Mantle

Tissue that secretes the shell in mollusks

Radula

Tongue-like organ for scraping in mollusks

Tagmatization

Fusion of body segments into specialized regions

Spiracle

Breathing hole opening to the tracheal system in arthropods

Deuterostomes

Animals where the mouth develops second, with the anus forming first