Zoology: Body plans Flashcards
Body plan
the basic shape of members of an animal phylum; the general structure each individual organism assumes as it develops.
Symmetry
the repetition of the parts in an animal or plant in an orderly fashion.
Cephalisation
presence of a definite head that contains sense organs.
Coelom
a large, fluid-filled cavity that lies between the body wall and internal organs, present in most triplobastic animals
Asymmetry
absence of or deviation from the regular disposition of similar parts of the body relative to a specific point, axis, or plane.
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.
Germ layers
any of three primary cell layers, formed in the earliest stages of embryonic development
Ectoderm
the germ layers on the outside of a 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 the ectoderm
Triploblastic
an organism that has 3 embryonic layers - ectoderm, mesoderm, endoderm
Acoelomate
an animal without a true body cavity
Pseudocoelomate
is an organism with body cavity that is not derived from the mesoderm, as in a true coelom, or body cavity.
