Demonstrating the Theory of Natural Selection
In 1976 two biologists, David Reznick of the University of California at Riverside and John Endler of the University of California at Santa Barbara, traveled to the West Indies island of Trinidad to begin the first in their inclusive series of studies concerning evolution. Their studies focused on the vast population of guppies. After over a decade of researching the guppies, the two biologists came to the conclusion that the guppies were able to evolve a great amount in a small duration of time. This not only supported Darwin's theory of evolution but more specifically his idea of natural selection. There was also one other theory which was very important, that was the life-history theory. This theory predicts that reduced adult survival will select for earlier maturation and increased reproductive effort. (Impact of predation) On other hand, reduced adolescent survival will select the opposite. This theory has only been proven in laboratory studies and cannot assess that of natural populations. In the experiment conducted by Mr. Reznick and Endler they support the predictions of the life-history theory with guppies.Natural populations of guppies (Poecilia reticulata), along the El Cedro and Aripo rivers, are found in
Even though a new species was not dealt with in the study, a significant increase in body size was. Body size is one of the principal traits used in paleontology to distinguish evolutionary changes and also was a major characteristic adapted by the guppies which were observed. Mr. Reznick and Endler believe that even though the rate of change seemed somewhat slow, there were significant changes which took place. They also said that if the study were to have gone for at least a thousand years we would have experienced a new species. (Evaluation of the rate) They also believe that the study shows that it is possible to use short term experiments of natural selection to gain a superior insight of evolutionary changes which occur over millions of years. They have also come to the conclusion that evolution by way of natural selection can occur very fast. In light of fossil records, it shows that natural selection is four to seven times faster. (Dawson) 2. Dawson, Jim. 'Guppy study suggests that natural selection can work out in The results reached by the biologists were extensive. Within two years the Their experiment took place in a rare river system in Trinidad where most of the fish are separated by waterfalls and rapids. They first moved the guppies from a high to low predation area. (Evaluation of the rate) They then took the guppies from locations below waterfalls on the Aripo and El Cedro rivers which contained numerous predators, and placed them in a tributary (experimental site) where only one predator existed, the Rivulus hartii. The high predation areas on the rivers were used as the controls. By doing that the biologists exposed the guppies to selective predation on adolescents instead of on the adults, like they were familiar with before. (Life history evolution.... Parallelism) The guppies used in the experimental site on the El Cedro river and the control site on the Aripo river, were brought up in a three-generation, extended-lineage, paternal half-sibling design. (Evaluation of the rate) 5. Reznick, D. A., Bryga, H. "Life history evolution in guppies. 1. Phenotypic and
Some common words found in the essay are:
Reznick Endler, El Cedro, Killifish Rivulus, West Indies, Cichlid Crenicichla, Reznick Experimentally, Cedro Aripo, Angeles Times, Dawson Jim, natural selection, Tribune Mar, life history, evaluation rate, life history evolution, history evolution, food availability, reznick endler, evolutionary changes, el cedro, control site, rivulus hartii, history evolution guppies, mar 28 1997, guppies poecilia peticulata, el cedro river,
Approximate Word count = 2076
Approximate Pages = 8 (250 words per page double spaced)
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