shnkrmn
Well-Known Member
A possible mechanism for evolution may be seen in the changing of frequency of expression of a genetic trait in response to environment over a period of time. This occurs in populations, not individuals. It has been a long time since I studied it, but I recall that one of the earliest observations of such a change in genetic expression was seen in a species of moth in England in the 19th century. This moth depended for survival on the camouflaging pattern and coloration of its wings allowing it to blend into tree bark in order to avoid being noticed by predators. In heavily industrialized parts of England,, where coal dust began to darken foliage and bark of trees, the population of such moths assumed, over time, a darker appearance as the phenotype of that moth which was darker was more successful at avoiding predators and thus was more successful at surviving to reproduce. This is an example of species adapatation. Note that this did not result in speciation, the light and dark moths were still the same species, but given enough time it was thought that the two populations might eventually become genetically differentiated enough that they would no longer breed together, leading to further differentiation and eventually an inability to interbreed; voila: two species where one was before. Because this happened in a relatively brief period of time, this is a poor example of 'evolution' but could illustrate one of the mechanisms by which one species can give rise to another.
Add in random mutation, isolation of populations such as the many species of finches which Darwin observed on the Galapagos islands and longer term forces such as the tectonic movement of continents, large scale global catastrophes such as asteroid impacts and you have a powerful recipe for diversification of life forms.
Add in random mutation, isolation of populations such as the many species of finches which Darwin observed on the Galapagos islands and longer term forces such as the tectonic movement of continents, large scale global catastrophes such as asteroid impacts and you have a powerful recipe for diversification of life forms.
