DEEP ETHOLOGY: evolution
ADAPTATION DEFINED


ADAPTATION DEFINED
.

"ADAPTATION" can be a confusing term because of the many ways it is used. For example, "adaptation" can refer to both processes and products:



Organisms can be viewed as complex, interconnected ensembles of anatomical, physiological, or behavioral TRAITS that contribute to FITNESS --an individual's ability to survive, thrive, and reproduce. A major quality animals must manifest is a capacity to COPE with challenges to its fitness. Ordinarily, there is no attribute of an organism that can be defined (including the relationships between attributes and the timing of their expression) that is not subject to natural selection


SO, when we speak of an organism's adaptations we are referring to traits subject to natural selection which persist because they contribute to fitness (or at least, contribute more than they cost). Adaptations are the means by which organisms cope with environmental changes and stresses.
An Adaptation can be manifest at any level of organization from subcellular through the ecosystem in which any level of organism -- environment conformity can be discerned. Within a single organism, "adaptation" can encompass morphology, physiology, development (through organizational effects or through differential timing of developmental events), and behavior.

ADAPTATION is a complex term because of the many ways it is used. It can refer to a TRAIT that confers some FITNESS on an animal, BUT it also represents the PROCESS by which that trait has come about.


ADAPTATION DEFINED

"adaptations are traits (or characters) that have been subjected to natural selection" This means that the trait has "evolved" (been modified during its evolutionary history) in ways that have contributed to the FITNESS of the organism manifesting it .
    DEFINITIONS (you would expect that such a key word has come to have many subtle nuances of meaning --BUT there IS an irreducible core of meaning which you must understand.)

    An adaptation is an anatomical, physiological, or behavioral trait that contributes to an individual's ability to survive and reproduce ("fitness") in competition with conspecifics in the environment in which it evolved (Williams, G. 1966. Adaptation and Natural Selection Princeton).


    Below is a definition by an anthropologist writing in the Annual Review of Ecology and Systematics. I like it because it touches every important base without becoming too diffuse:

      Adaptation is . . .

      "The processes by which organisms or groups of organisms maintain homeostasis in and among themselves in the face of both short-term environmental fluctuations and long-term changes in the composition and structure of their environments." (Rappaport, 1971).


The several senses of the term "adaptation" have something in common --the idea of compensation for change:

ADAPTATIONISM -- is a term that is sometimes used in a negative sense to refer to an explanation for a trait that uncritically applies evolutionary ideas. Others use the term in a positive sense to refer to speculative hypotheses about how a trait may have come about. [more on adaptationism]



..

|