Life 103 Exam 3

Body Symmetry

Refers to the arrangement of body parts in an organism, can be radial or bilateral.

Bilateral Symmetry

A condition where one half of an organism is a mirror image of the other half.

Radial Symmetry

A condition where similar parts are arranged regularly around a central axis.

Diploblastic

Refers to animals that have two tissue layers: endoderm and ectoderm.

Triploblastic

Refers to animals that have three tissue layers: endoderm, mesoderm, and ectoderm.

Coelom

A true body cavity that is formed from mesoderm.

Pseudocoelom

A body cavity that is derived from both mesoderm and endoderm.

Protostome Development

Embryonic development that is determinate and spiral with the mouth formed from the gastrula.

Deuterostome Development

Embryonic development that is radial and indeterminate, with the anus formed from the gastrula.

Choanoflagellates

The closest living relatives to animals.

Cleavage

The rapid cell division that occurs in an embryo after fertilization, leading to the formation of a blastula.

Blastula

A hollow ball of cells formed during the early embryonic development.

Gastrulation

The process that transforms the blastula into a structure with three tissue layers: endoderm, ectoderm, and mesoderm.

Homeostasis

The maintenance of internal balance despite external changes.

Negative Feedback

A regulatory mechanism that counteracts a change, returning a variable to its normal range.

Positive Feedback

A regulatory mechanism that amplifies a response, increasing the effect of a change.

Convergent Evolution

The phenomenon where different organisms develop similar traits due to similar environmental pressures.

Nervous and Muscle Tissue

Defining characteristics of the animal kingdom.