Glossary of Plant Systematics (1st ed.) by Simpson (2006)
- A structure or feature that performs a particular function and which results in increased survival or reproduction.
Glossary of Evolution (2nd ed.) by Futuyma (2009)
- A process of genetic change in a population whereby, as a result of natural selection, the average state of a character becomes improved with reference to a specific function, or whereby a population is thought to have become better suited to some feature of its environment. Also, an adaptation: a feature that has become prevalent in a population because of a selective advantage conveyed by that feature in the improvement in some function.
Glossary of Ecology (6th ed.) by Krebs (2009)
- any alteration in the structure or function of an organism by which the organism becomes better able to survive and multiply in its environment.
- Futuyma, D. J. 2009. Evolution, 2nd ed. -xviii + 633 pp. Sinauer Associates, Inc., Sunderland.
- Krebs, C. J. 2009. Ecology, 6th ed. -xvi + 655 pp. Pearson Benjamin Cummings, San Francisco.