What is evolution?

Evolution is the gradual change of an organism over time. Both the period of time and the changes of a given organism may vary greatly.

Evolution is typically thought of as something that happens over millions, or even billions of years. Science has proven that evolution can happen in as little as 11 years. An example of this can be found in the Biology 141 text book, Biology by Neil Campbell and Jane Reece. In this example, some scientist studied two groups of Guppies found in isolated environments. One environment had a predator fish called a Killie Fish while the other environment had the Pike Cichlid. Killie Fish prey on smaller animals, as they are a small fish. Pike Cichlids grow fairly large so they have large prey items. Scientists found that the guppies in the isolated pool with Killie Fish grew larger than those found in the pool with the Pike Cichlids. These findings would seem to indicate that the guppies in the pool with the Killie Fish evolved to be a larger size in order to avoid becoming preyed upon.

To verify these findings scientist collected guppies from a pool with Pike Cichlids and introduced them to a pool with Killie Fish instead of Pike Cichlids. They monitored them over a course of 11 years and several generations and found that the guppies had a larger over all size and weight, when compaired to the orginal stock Guppies, had increased by 14%.

Organisms evolving may seem like something that they choose to do, but this is not the case. Evolution happens at random. Organisms can not choose to produce an evolutionary trait. Mutations are a key factor in evolution. An organism’s genetics can mutate (change) due to several reasons, from exposure to chemicals or radiation to inbreeding. These mutations are not always beneficial; in fact some cause the organism’s death. Say a bird was to develop a mutation where its flight feathers were nonexistent. This bird would surely fall prey to another organism due to its newly acquired mutation. Since the bird with this particular mutation was eaten, its ability to breed with another bird and pass on the genes with the “no flight feathers” mutation is not possible. This is an example of Darwin’s “survival of the fittest” theory.

From generation to generation, mutations will inevitably happen. Only organisms which have advantageous mutations will survive to pass on their genetics. Once the advantageous mutations are in the “gene pool” future generations may exhibit this advantageous trait. Later on, another mutation will, again, inevitably occur. If the mutation is beneficial, the species has acquired yet another beneficial trait.

Evolution typically occurs as an adaptation to a change in an organism’s environment. An example of this would be continental drift. If a population of organisms was split due to continental drift, they would evolve differently. If one portion of land affected by the split were to drift north (in the northern hemisphere) the organism on this portion of land would most likely develop (evolve) traits which are beneficial to living in cold weather. This is how different species emerge; a population is split up becoming two populations that evolve differently to fit their environment. Over millions, or billions of years and even more generations, these small changes can cause an organism to look completely different.