∞ generated and posted on 2016.12.15 ∞
Change in allele frequencies within populations as a function of time.
| Evolution is the origin of all that is biology. |
"Change in allele frequencies… as a function of time" is the population genetics definition of what organic evolution consists of. The word "change" is key, however, and is shared with other definitions of evolution, as too is the word, "time".
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The following video provides an introduction to evolutionary biology:
The word "population" is also crucial. Individual organisms do not evolve but, instead, it is populations that evolve. That is, allele frequencies within a given individual are more or less fixed while allele frequencies within populations are not. Furthermore :
When Dobzhansky (1973) famously argued that "nothing in biology makes sense except in the light of evolution" he could as well have added that "(almost) nothing in evolution makes sense except in the light of function."
Figure legend: Changes in allele frequencies, the basis of evolution, can occur by a number of mechanisms. Here these are differentiated into those that can play a substantial role in adding alleles to populations versus those that can play a substantial role in taking alleles out of populations. The word 'substantial' is important in these descriptions as mutation, in particular, can take alleles out of populations, though generally this occurs at fairly low rates. In any case, by adding or taking what is being referred to is numerical changes rather than necessarily the addition or removal of all copies of a given allele within a given population.
Cancer – which consist of defector cells that arise within bodies through mutation and which increase in frequency due to selection – might be viewed as a counter argument to the idea that evolution is a property of populations, rather than of individuals. Instead, however, this example supports the previous point quite well: Cancers represent changes in allele frequencies among the population of cells making up individual, multicellular bodies. Evolution, that is, is a change in allele frequencies within populations as a function of time, with the concept of population potentially varying in its specifics going from situation to situation.
Figure legend: Evolution broadly consists of what traditionally is described as a combination of microevolution and macroevolution, with speciation serving as the connection between these two aspects of evolution. Microevolution in particular is evolution as it occurs within species whereas macroevolution is that which occurs essentially between species.
From :
It is now evident that the terms teleology have been applied to two entirely different sets of phenomena. On one hand is the production and perfecting throughout the history of the animal and plant kingdoms of ever-new programs and of ever-improved DNA codes of information. On the other hand there is the testing of these programs and the decoding of these codes throughout the lifetime of each individual. There is a fundamental difference between, on the one hand, end-directed behavioral activities or developmental processes of an individual or system, which are controlled by a program, and, on the other hand, the steady improvement of genetic codes. This genetic is evolutionary adaptation controlled by natural selection.
See also microevolution and macroevolution. For a list of additional terms associated with the study of evolution, see evolutionary biology.
The following video provides an introduction to evolutionary biology:
The following video provides a lovely look at where, functionally and morphologically, our eyes came from:
The following is a powerful video that does a good job of laying out the various concepts underlying especially the concept of common descent:
And here we have a look at the evolution of whales:
The following video discusses crocodile teeth that are differentiated like those of mammals:
The following video walks through the wonderful story of the evolution of horses:
Video (Introductory lecture covering the rise of the ideas of evolution and microevolution)