Sunday, March 7, 2010
Longevity of Life or Swiftness of Reproduction?
In Chapter 1, Jerry Coyne discusses how Ginkgo Trees and horseshoe crabs have not evolved much over the millions of years that it has existed. Compared to small bacteria that can reproduce after existing for only several minutes, why is it that ginkgo trees and horseshoe crabs have not been out-competed or eliminated? Ginkgo trees can live for hundreds and sometimes even thousands of years, does this mean that those that can survive longer are a "fitter" form? or does a smaller organism that does not live long but can reproduce at a much quicker rate, therefore, have a greater chance of a "fitter" mutation to occur be more preferable as time moves forward? or is there some compromise in between that produces the "ideal" organsim?
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ReplyDeleteI'm sorry. I'm kind of confused about your prompt.
ReplyDeleteAre you asking whether an organism's more fit if they live longer or more fit if they could reproduce more rapidly, or are you asking a completely different question?
Henry, that does seem to be what he is asking.
ReplyDeleteI think that the quicker rate of reproduction will lead to more mutations, and as a result, greater genetic diversity. However, the longevity of life may show that organisms such as ginko trees do not necessarily need to change. Despite that apparent lack of weakness, if something were to threaten the ginko trees, the ginko trees may not actually be able to adapt quickly enough.
Longevity of life, unlike extremely quick reproduction, is not a cause of of evolution. In the end, the fact that ginko trees and horshoe crabs have not evolved much over such a long period of time seems to indicate that the organims are already well-adapted to their lifestyles, so further genetic mutations may do more harm than good.
I agree with Dennis’s point that ginkgo trees and horseshoe crabs haven’t evolved much in part because there is no need, since these organisms are comfortable in their present environments and well-adapted. However, if something were to happen that disturbed the present environment of ginkgo trees and horseshoe crabs, these organisms would be in trouble. Let’s say there was some sort of natural disaster in an area where ginkgo trees lived. Since bacteria on the ginkgo trees reproduce quickly, there is more genetic variation, and natural selection would be able to favor the bacteria that can survive in the new environmental conditions that the disaster has created (ex: surviving with less water, or in higher temperatures). Unfortunately, the ginkgo trees might not survive the disaster, nor will there be time for the trees to reproduce in hope that one of the offspring has a mutation allowing it to survive in these new conditions. Coyne discusses the second part of evolutionary theory, gradualism, as an idea saying “it takes many generations to produce a substantial evolutionary change.” (4)The fact is, since organisms like ginkgo trees live longer, there is a lot more time between generations, and the evolutionary process is slowed.
ReplyDeleteTo answer the question as to which type of organism is ‘fitter’, we need to look at the theme of continuity and change. Really, it depends on the environment. As long as a ginkgo tree’s habitat remains stable, these organisms are in no danger and there isn’t anything wrong with slower evolution of this specie. However, when the environment is constantly in flux, natural selection will favor organisms that reproduce rapidly (like bacteria), since these organisms can adapt quicker to new situations.