∞ generated and posted on 2016.12.04 ∞

Morphological, physiological, biochemical, or behavioral aspects of organisms that contribute to their evolutionary fitness.

That definition of adaptation can be complicated in various ways:

  1. The definition as given is in terms of its use as a verb. The same word, however, also can be used instead as a noun, meaning a product of the process of adaptation.

  2. An adaptation, rather than being an evolutionary response by a population to some environmental factor, instead can be a physiological response of an organism to an environmental change, that is, a response that has a genetic and therefore evolutionary origin, but which does not in its implementation involve genetic changes to the organisms that are so responding.

The rest of this entry considers adaptation particularly from an evolutionary perspective.

Figure legend: Examples of adaptations.

Adaptations typically are the products of a combination of mutation and natural selection. Mutation supplies variation to populations and particularly relevant is genetic variation that results in phenotypic variation in terms of morphology, physiology, biochemistry, or behavior.

Genetic variation, i.e., alleles that results in greater organism reproductive success, tends to both persist over time and encode traits that contribute to that greater reproductive success.

Note that adaptations tend to be the products of multiple mutations, all of which individually or in combination have stood the test of natural selection. In particular, it is against a genetic background of successful and/or fixed mutations that new mutations tend to occur within populations.

The following video considers the adaptive evolution of the eye:

In other words, populations not only tend to generate novel mutations in their hereditary material – due to some level of infidelity during replication – but at least some of those new mutations are maintained within populations, with biases towards those mutations that help to increase organism fitness.

The genetic backgrounds within which new mutations occur therefore tend to be ones that are already adaptive, with biases towards retention of those mutations that contribute additional adaptations.

The rich, as they say, tend to get richer!

See also beneficial allele, beneficial mutation, convergent evolution, etc.