4.1. 3: Evolution and Isolation

January 14th, 2010

Evolution is defined as the change in the gene pool of a population over time. This is a continuous process. Each generation of humans has a different genetic mix than their parents: they have evolved. however the common, and confusing notion of evolution is that it is about creating new species - speciation.

Speciation is only one path which evolution can take and requires certain driving conditions to operate for it to occur. One driving condition for evolution that can lead to the development of new species is isolation.

First though it is important to understand the idea of species. The most common definition of a species is a group of organisms that interbreed to produce fertile offspring. So using this definition it is clear to see that horses and donkeys are two different species - they can breed together and produce off spring, a mule, but mules are infertile and can not reproduce themselves.

Evolutionary changes that could see the development of a new species involves changes in gene pools of a pre-existing species that lead to the inability to produce fertile offspring. Those changes are often brought about by isolating mechanisms. The diagram above show a theoretical situation where isolation of two beetle populations from an original bigger population could lead to speciation.

Mechanisms of isolation can be physical or social. Major events such as earthquakes, volcanic action, flooding or other catastrophes can create isolated populations. Social mechanisms of isolation include emigration from a population to create a new smaller isolated population. Often though both physical and social isolation occur together. A new volcanic island will be colonised by animals that have emigrated from a continental population.

Evidence for these processes occurring can be seen in subspecies of many animals where isolation of parts of a large population have been isolated over a long time from a continental cousin and noticeable changes, in morphology or behaviour in the isolated population has occurred compared to the ancestor population. The Svladbard Rheindeer are a very good example of these process in action.

Send article as PDF to PDF Download
Comments are closed.