Biological variability first, from the point of view of evolutionary theory.?

Please help me with some of my difficulties : I am reading human evolution book.





What is the importance of biological variability first, from the point of view of evolutionary theory.





When was the importance of variability to the concept of evolution first recognized and by whom? - I think by DARWIN .... am I right ?





And, second, from the point of view specifically in explaining variability in modern human populations. Discuss models that have been used to explain how variation appears in populations. ---- I think skin color, blood types etc ........Right ?





Please Help asap

Biological variability first, from the point of view of evolutionary theory.?
Darwin developed his theory of Natural Selection during the Beagle expedition. He was particularly influenced by the "Galapagos Islands.





Here's how one site explained the evolution of the Galapagos Island





"Darwin's observations, specifically on what are now called "Darwin's Finches," regarding the adapted species that existed on the islands eventually provided the basis for his Theory of Natural Selection. Explained briefly, the concept of the evolution of species is based on a number of characteristics of survival and reproduction. In most populations, the number of species is larger than the available resources and competition is inevitable. Within the normal variation that occurs in species, occasionally a mutation or difference will occur that will be somehow advantagous to survival or breeding, and those with the positive change will have a greater number of offspring. As the offspring are likely to receive these same genetic advantages, they also will be more likely to survive and pass on their genes. Those best adapted to their environment, best specified and best adaptive will survive. "


http://www.galapagosislands.com/html/evo...





In a nutshell that explains the importance of biological variability. With humans we all have two eyes, ears, a nose and mouth. Yet there's enough variation that we can quickly identify individuals.





Given a species certain variations will mean individuals will do better. They are more likely to mate and pass on their genes. Over time evolution takes place. It was noted that some females of a species of birds mate with males that have the most colorful plumage. When the males were examined it was found that those with the brightest feathers were the most resistant to mites that attacked the feathers.





Darwin wasn't the first to discuss natural selection, his publications did bring it to the attention of scientists and the public.





In the human population the variation of skin color is noticeable. Darker skin is found in the equatorial regions and in the higher latitudes lighter skin predominates. In the great migration out of Africa human skin color changed based on environmental needs. Darker skin was an protection in hot sun, while light skin was more effective where there was less sun. As one site reports "Fair-skinned individuals who sunburn easily and tan minimally or not at all have a higher incidence of skin cancer than dark-skinned individuals"


http://www.skincancer.org/basal/index.ph...





While you'll see the word "mutation" applied to evolution, variability within the population no doubt provides much of the change is a species
Reply:variability allows natural selection to take place, meaning that there are different traits that allow better fitness
Reply:Without variation of organisms natural selection would have nothing to select. The variations are distributed normally, that is some are beneficial, some are detrimental and some are neutral. In the struggle for existence and especially mates, a small beneficial variation can allow you to leave more decedents, some of which carry the variation down the generations. This entails a change in allele frequency and mover the population in the direction of the beneficial variation.


Think skin color. A mutation that allowed more melanin into the skin in a very sunny latitude would be favored by natural selection, as the possessors of this trait would have an advantage, however so small, of leaving more descendants.
Reply:1) Darwin was not the first to acknowledge variation and its role in evolution, but he did accurately explain how variation acts in evolution.





2) Humans actually have extremely low genetic variation compared to other animals, including chimpanzees. This is likely due to the fact that our ancestors experienced a bottle neck or significant decrease in population around 70,000 years ago. Humans have such diverse phenotypes since they occupy the most diverse niches and biogeography out of any mammal.

dendrobium