Zoology: Evolutionary History of Animals Flashcards
symmetry
the symmetry observed in organisms, including plants, animals, fungi, and bacteria.
cephalization
the presence of a definite head that contains sense organ. This feature is first seen in the phylum Platyhelminthes.
coelom
a large, fluid-filled cavity that lies between the body wall and internal organs, present in most triploblastic animals
radial symmetry
symmetry about a central axis, as in a starfish or a tulip flower.
bilateral symmetry
symmetry in which similar anatomical parts are arranged on opposite sides of a median axis so that only one plane can divide the individual into essentially identical halves.
ectoderm
germ layer on the outside of diploblastic animals that gives rise to the epidermis and nervous tissue.
endoderm
the germ layer on the inside of diploblastic animals that gives rise to the gut and its organs
mesoderm
the layer of embryonic cells lying between the ectoderm and the endoderm in all higher animals which gives rise to muscle, the blood system, connective tissues, the kidney, the dermis of the skin and the axial skeleton.
diploblastic
having a body wall that is composed of two layers - the endoderm and ectoderm
triploblastic
an organism that has three embryonic layers - ectoderm, mesoderm and endoderm
coelomate
animals with a body cavity called a coelom with a complete lining called peritoneum derived from mesoderm (one of the three primary tissue layers)
acoelomate
an animal without a true body cavity
pseudocoelomate
an organism with body cavity that is not derived from the mesoderm, as in a true coelom, or body cavity.
through gut
alimentary canal, digestive tract.
blind ended gut
a digestive cavity open at only one end especially : the cecum of the large intestine.
