Based on his findings and observations from his travels along with his discussions with fellow scientists of the time, Charles Darwin conceived the theory of natural selection which explained how species originated from common forms and diversified over geological time. Although the immenseness of this theory was not fully grasped at the time, the theory of natural selection may have been the most important idea in the theory of evolutionary processes. However the mechanism by which natural selection causes ‘genetic evolution’ of a species was only later realised when the experiments of Mendel’s publication were discovered.
Example
For the purpose of explaining evolution I would like to cite the classical example of the peppered moth (Biston betularia). This example is taken from the lecture (1) as part of this course. To me this came across as a striking example of the outcome of the driving force of natural selection.
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In England, at the time of the industrial revolution through studies on museum collections it was found that the frequency of darker morphs was increasing and those of the lighter were decreasing sharply (2). The reason was thought to be that with the onset of the industrial revolution, came a change in colour of tree trunks due to deposition from air pollution. This increased the conspicuousness of the lighter morph and helped the darker to camouflage better from predators. Thus the lighter morphs were more visible to predators and hence more frequently selected against. Through later experiments (3) it had also been shown that the agent of this selection had been birds that predate on the