Science / Marine Biology Glossary

Density-Dependent Factors: Factors, such as resource availability, that vary with population density

Deoxyribonucleic acid (DNA): The primary genetic material of a cell that makes up genes and chromosomes. See also genes, chromosome.

Deposit Feeder: An organism that derives its nutrition by consuming some fraction of a soft sediment

Detritus: Particulate material that enters into a marine or aquatic system. If derived from decaying organic matter it is organic detritus.

Detrivore: An organism that feeds on large bits of dead and decaying organic matter. What detrivores leave behind is used by decomposers. Crabs and seabirds are examples of detrivores. Compare decompos . . . View Full Definition

Diatom: Dominant planktonic algal form with siliceous test, occurring as a single cell or as a chain of cells

Diffusion: The net movement of units of a substance from areas of higher concentration to areas of lower concentration of that substance

Digestion Efficiency: The fraction of living food that does not survive passage through a predator's gut

Dinoflagellate: Dominant planktonic algal form, occurring as a single cell, often biflagellate

Directional Selection: Preferential change in a population, favoring the increase in frequency of one allele over another

Dissolved Organic Matter: Dissolved molecules derived from degradation of dead organisms or excretion of molecules synthesized by organisms

Disturbance: A rapid change in an environment that greatly alters a previously persistent biological community

Divergent Evolution: The evolution of one species to a number of different forms. Compare convergent evolution; see also evolution.

Diversity: A parameter describing, in combination, the species richness and evenness of a collection of species. Diversity is often used as a synonym for species richness

Diversity Gradient: A regular change in diversity correlated with a geographic space or gradient of some environmental factor

Ecological Niche: The role a plant or animal plays in its community. The niche of an organism is defined by what it eats, its predators, salt tolerances, light requirements etc. Two species cannot live stably . . . View Full Definition

Ecology: The study of the physical and biological interactions between an organism and its natural environment.

Ecosystem: A community of plants, animals and other organisms that are linked by energy and nutrient flows and that interact with each other and with the physical environment. Rain forests, deserts, co . . . View Full Definition

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