Heredity, Natural Selection, and Evolution

Highlights of Evolution

Is it possible to observe evolutionary change in other species?

Industrial melanism is the change in the coloration of species that occurs as a result of industrial pollution. Increased air pollution as a result of the Industrial Revolution in Great Britain during the eighteenth and nineteenth centuries led to an accumulation of soot on many structures, including tree trunks. As a result, organisms whose coloration allowed them to use the trees to hide from predators lost that advantage and were eaten more often by predators. A classic example of this was the peppered moth (Biston betularia), whose coloration is polymorphic. Prior to the Industrial Revolution, collection records indicate that the darker or melanistic form was almost unknown, but by 1895 it constituted about 98 percent of the moths collected. The two forms eventually reached a state of balanced polymorphism. Because the change in morphology could be directly linked to the change in industry, this process is described as industrial melanism.

Yes, the change within populations, which is driven by natural selection, is occurring around us constantly. However, whether we can actually observe those changes is a different matter. For example, elephants may be adapting to changing conditions in their environment, but since they tend to be extremely long-lived, it is unlikely that we will be able to follow enough generations to observe a trend. On the other hand, it is possible to notice such changes in populations of individuals with very short life spans, particularly when they are experimentally manipulated. For example, bacteria and guppies are just two species that have been observed evolving in response to changing environmental conditions.


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