Animal Architecture: Levels of Organization and Symmetry

These flashcards cover key concepts regarding animal architecture, including levels of organization, symmetry, reproduction, and body cavities.

Protoplasmic

The simplest level of organization found in unicellular organisms such as protozoans.

Cellular

A level of organization characterized by a colonial arrangement of undifferentiated cells or multicellular animals with specialized cells, exemplified by sponges.

Tissue

A level of organization where similar cells are grouped together for specific functions, seen in cnidarians.

Organ

A level of organization formed when tissues are assembled into functional organs, as observed in flatworms.

System

A level of organization where multiple organs work together for a common function, typical in most animals.

Radial symmetry

A body plan that can be divided into two or more equal parts around a central axis, common in sessile or weakly swimming animals.

Bilateral symmetry

A body plan that can be divided into two mirror-image halves along a single plane, associated with directional movement and cephalization.

Cleavage

The series of rapid cell divisions of the zygote after fertilization, leading to the formation of a multicellular structure such as a morula.

Blastula

A hollow ball of cells formed during early development, preceding the gastrulation stage.

Gastrula

An embryonic stage characterized by the folding of the blastula and formation of germ layers.

Diploblastic

Organisms with two germ layers: ectoderm and endoderm, such as cnidarians.

Triploblastic

Organisms with three germ layers: ectoderm, mesoderm, and endoderm, typical of bilateral animals.

Coelom

A fluid-filled body cavity that cushions organs and allows them to develop independently from the body wall.

Acoelomate

Animals that lack a body cavity between the gastrointestinal tract and the body wall.

Pseudocoelomate

Animals that have a body cavity that is not fully lined by mesoderm.

Coelomate

Animals with a true body cavity fully lined by mesoderm.