Animal Body Plans and Structures

These flashcards cover essential vocabulary and key concepts related to animal body plans, symmetry, skeletons, cephalization, and tissue organization.

Symmetry

A property of shape where parts are arranged around a central axis.

Asymmetry

Lack of symmetry; no identifiable symmetry in structure.

Radial symmetry

Symmetry where the body can be divided into equivalent halves through multiple planes through a central point.

Bilateral symmetry

Symmetry where the body is divided into equal right and left halves along one central plane.

Skeleton

The internal or external structure that supports the body and protects organs.

Hydrostatic skeleton

A skeleton formed by fluid-filled cavities, providing structural support through pressure.

Endoskeleton

A hard internal skeleton supporting the body from within, covered by skin or other tissues.

Exoskeleton

A hard external skeleton that provides protection and structure for movement.

Cephalization

The development of a head that contains sensory structures and a brain.

Segmentation

The division of an organism's body into repeated sections or segments.

Germ layers

The distinct layers (endoderm, mesoderm, ectoderm) formed during embryonic development that give rise to various tissues and organs.

Endoderm

The innermost germ layer in the embryo, giving rise to internal structures like the digestive tract.

Mesoderm

The middle germ layer in the embryo, forming muscles, skeletal structures, and circulatory systems.

Ectoderm

The outermost germ layer in the embryo, developing into the outer covering and nervous system.

Coelom

A fluid-filled body cavity that separates the digestive tract from the body wall.

Coelomates

Organisms with a true coelom formed from mesoderm tissues.

Pseudocoelomates

Organisms with a body cavity formed from both mesoderm and endoderm tissues.

Acoelomates

Organisms that lack a body cavity altogether.

Cnidocytes

Specialized cells in cnidarians containing nematocysts for capturing prey.

Nematocysts

Stinging structures within cnidocytes that inject toxin into prey.

Gastrovascular cavity

A central cavity in certain animals where digestion and absorption occur.

Radula

A rasping organ in mollusks used for feeding.

Mantle

A layer of tissue that covers the body of mollusks and secretes shells.

Echinoderms

A phylum of marine animals characterized by radial symmetry, a water-vascular system, and an endoskeleton.

Adaptive advantages of segmentation

Allows for greater mobility, functionality in body sections, and specialization of segments for different purposes.

Trochophore

A larval stage in some mollusks and annelids characterized by a band of cilia.

Ganglia

Clusters of nerve cells that process information and coordinate actions.