Science / Biology Glossary

Cleavage Furrow: A constriction of the cell membrane at the equator of the cell that marks the beginning of cytokinesis in animal cells. The cell divides as the furrow deepens.

Climax Community: The stage in community succession where the community has become relatively stable through successful adjustment to its environment.

Clitoris: A short shaft with a sensitive tip located where the labia minora meet; consists of erectile tissue and is important in female sexual arousal.

Clone: An exact copy of a DNA segment; produced by recombinant DNA technology.

Closed Circulatory System: A system that uses a continuous series of vessels of different sizes to deliver blood to body cells and return it to the heart; found in echinoderms and vertebrates.

Closed Community: A community in which populations have similar range boundaries and density peaks; forms a discrete unit with sharp boundaries.

Codominance: A type of inheritance in which heterozygotes fully express both alleles.

Codon: A sequence of three nucleotides in messenger RNA that codes for a single amino acid.

Coelom: In animals, a body cavity between the body wall and the digestive system that forms during preadult development.

Coelomates: Animals that have a coelom or body cavity lined with mesoderm.

Coenzymes: Chemicals required by a number of enzymes for proper functioning; also known as enzyme cofactors.

Cohesion: The force that holds molecules of the same substance together.

Cohesion-Adhesion Theory: Describes the properties of water that help move it through a plant. Cohesion is the ability of water molecules to stick together (held by hydrogen bonds), forming a column of water extendin . . . View Full Definition

Collenchyma: One of the three major cell types in plants; are elongated and have thicker walls than parenchyma cells and are usually arranged in strands; provide support and are generally in a region tha . . . View Full Definition

Colonial: 1. Level of organization intermediate between unicellular and multicellular - organisms are composed of multiple cells but fail to exhibit specialization of those cells. Examples: Volvox, a . . . View Full Definition

Commensalism: A symbiotic relationship in which one species benefits and the other is not affected.

Community: All species or populations living in the same area.

Community Age: One of the factors that helps cause the latitudinal diversity gradient. Tropical communities have had more time to evolve because they have been less disrupted by advancing ice sheets and ot . . . View Full Definition

Community Simplification: The reduction of overall species diversity in a community; generally caused by human activity.

Community Succession: The sequential replacement of species in a community by immigration of new species and by local extinction of old ones.

Compact Bone: The outer dense layer that forms the shaft of the long bones; made up of concentric layers of mineral deposits surrounding a central opening.

Companion Cells: Specialized cells in the phloem that load sugars into the sieve elements and help maintain a functional plasma membrane in the sieve elements.

Competition: One of the biological interactions that can limit population growth; occurs when two species vie with each other for the same resource.

Competitive Exclusion: Competition between species that is so intense that one species completely eliminates the second species from the area.

Competitive Release: Occurs when one of two competing species is removed from an area, thereby releasing the remaining species from one of the factors that limited its population size.

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