Animal Biology Study Guide for Exam III

A collection of vocabulary terms and their definitions to aid in the preparation for the upcoming biology exam focusing on animal biology.

Heterotroph

An organism that obtains organic food molecules by eating other organisms or their byproducts.

HOX genes

A group of related genes that control the body plan of an embryo along the head-tail axis.

Parthenogenesis

A mode of asexual reproduction in which an egg develops into an organism without fertilization.

Cephalization

The evolutionary trend in which the nervous system and sensory organs become concentrated at the anterior end of an organism.

Triploblastic

Organisms that have three germ layers: ectoderm, mesoderm, and endoderm.

Diploblastic

Organisms that have two germ layers: ectoderm and endoderm.

Gastrulation

The phase early in the embryonic development of animals during which the single-layered blastula is reorganized into a multi-layered structure known as the gastrula.

Acoelomate

An organism that lacks a coelom, or body cavity.

Pseudocoelomate

Organisms that have a body cavity that is not entirely lined by mesoderm.

Coelomate

An organism that possesses a true coelom, a body cavity completely lined with mesoderm.

Radial symmetry

Body plan in which body parts are arranged around a central axis, like a wheel.

Budding

A form of asexual reproduction in which a new organism develops from an outgrowth or bud on the parent.

Nematocysts

Specialized cells in cnidarians that contain a toxin to immobilize prey.

Trochophore

A type of free-swimming larva with two bands of cilia, common in several phyla of aquatic invertebrates.

Ectoprocts

Aquatic animals with a lophophore, also known as bryozoans.

Metamorphosis

A biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure.

Endoparasite

A parasite that lives within the body of its host.

Schizocoelom

A type of coelom that is formed by the splitting of the mesoderm.

Enterocoelom

A type of coelom that develops from pouches that bud off from the gut.