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bubblybiishh

What does the continued presence of vestigial structures like the whale pelvis and femur shown in Figure 16-1 suggest about the impact vestigial structures have on fitness?

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  2. Koikkara
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    Vestigiality describes homologous characters of organisms which have seemingly lost all or most of their original function in a species through evolution. These may take various forms such as anatomical structures, behaviors and biochemical pathways. Some of these disappear early in embryonic development, but others are retained in adulthood. Although the term serves a purpose in many gross phenotypic characteristics, vestigial has probably little applicability to DNA sequences, be they genes or non-coding sequences. The term junk DNA is a revealing example. It is a value or judgmental term which has become less utilized in genetics as many of the sequences once believed to be “junk” have been discovered to have a function. Vestigial structures are often called vestigial organs, although many of them are not actually organs. These are typically in a degenerate, atrophied, or rudimentary condition,[1] and tend to be much more variable than similar parts. Although structures usually called "vestigial" are largely or entirely functionless, a vestigial structure may retain lesser functions or develop minor new ones.[2] However, care must be taken not to apply the label of vestigiality to exaptation, in which a structure originally used for one purpose is modified for a new one. For example, the wings of penguin or ostrich would not be vestigial, as they have been modified for a substantial new purpose (underwater locomotion or display respectively), while Darwin pointed out that those of an emu would be, as they have no major function now. Vestigial characters range on a continuum from detrimental through neutral to marginally useful. Some may be of some limited utility to an organism but still degenerate over time; the important point is not that they are without utility, but that they do not confer a significant enough advantage in terms of fitness to avoid the random force of disorder that is mutation. It is difficult however to say that a vestigial character is detrimental to the organism in the long term - the future is unpredictable, and that which is of no use in the present may develop into something useful in the future. Vestigiality is one of several lines of evidence for biological evolution. Contents http://answers.yahoo.com/question/index?qid=20090525133555AA9bvgq

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