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User:TonySidaway/Evolution (view source)
Revision as of 00:15, September 15, 2012
, 00:15, September 15, 2012→Population thinking
An alternative to this species thinking which is often adopted by modern biologists, is population thinking. A population is a group of organisms that interbreed. If river flooding or some other force should isolate some members of a population from others, then the members of the isolated group become a new population. Since descendants get their characteristics from their ancestors, this provides a coherent alternative to the platonic species concept. This new thinking allows naturalists to think about what happens to a population that is isolated in such a way? Does it mirror the population from which it is derived, or does it change? Could such change help to explain why organisms, both in modern day and as represented by fossils, appear so well adapted to their circumstances?
An alternative to this species thinking which is often adopted by modern biologists, is population thinking. A population is a group of organisms that interbreed. If river flooding or some other force should isolate some members of a population from others, then the members of the isolated group become a new population. Since descendants get their characteristics from their ancestors, this provides a coherent alternative to the platonic species concept. This new thinking allows naturalists to think about what happens to a population that is isolated in such a way? Does it mirror the population from which it is derived, or does it change? Could such change help to explain why organisms, both in modern day and as represented by fossils, appear so well adapted to their circumstances?
==Natural selection==
Species have a degree of plasticity, this was known from the earliest times, but understanding adaptation--how species tend to be fitted to their circumstances--took many iterations. Somehow, it seemed, successive generations must become better at doing what they did, but how could this be so if each generation had to start anew as a seedling, or as a newly hatched or newly born animal?
A milestone on this route, which was not fully abandoned until the mid-20th century, was the notion that the experiences of the parent are somehow transmitted to the offspring. This led to an explanation of adaptation that relied on the observation that many organisms adapt during their lifetimes. Thus in cold conditions many species of mammal do react by growing more fur.