Through evolution, biodiversity is increased and species either adapt or become extinct. The four forces of evolution combine in methods that create either a stronger or weaker species. Stronger species will withstand the forces of nature. Weaker species will die off as their flaws are exposed to the evolutionary forces. The four forces of evolution include mutations, gene flow, genetic drift and natural selection. In order to explain these concepts, one must have an understanding of several concepts.

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In biology, a species refers to any group of organisms that have the capability to interbreed and produce fertile offspring. This second part is important because there are cases where two different species can breed and produce a viable offspring. A male donkey and a female horse can breed together and produce a live offspring, the mule. However, mules are sterile and cannot breed. In biology, a population refers to a group of the same species that live in the same area and thus interbreed. An example of this would be all the Empire penguins living within one region. There are isolating mechanisms that prevent genetic material from mixing with other species and populations. For instance, penguins living in South Africa and penguins living in the South Pole clearly have an isolating mechanism simply due to geography. However, similar species that live in the same area may not reproduce because they cannot produce a viable offspring. They may not be able to physically reproduce. They may also have a variety of biological rhythms, such as circadian cycles or hibernation which separates them in time. The female of the species may not be in estrus at the correct time. All of these forces work together to keep genetic material separated.

By all means though, genetic material does flow between groups. Gene flow or gene migration refers to how genes are transferred from one population to another. As species breed with each other, genetic material is passed back and forth. This decreases the genetic diversity in the groups. As a result, this mechanism serves to reduce speciation. Speciation occurs when a new species develops. This is normally due to the genetic material being separated. As the species adapts to new surroundings, a new species is often created. In particular, islands are known places for speciation to occur. As the island separated from the mainland during plate movements, species were cut off from their entire population. Over time, the diminished ability for gene flow and the new environment will give rise to a new species.

Genetic drift is another important concept for an understanding of evolution. Genetic drift is a product of random sampling. When two parents reproduce, the offspring will randomly inherit various traits. In this part of evolution, chance plays a significant role. Chance determines which animals will become parents. Chance also determines if the offspring has a better or worse chance of survival. Penguins that have difficulty swimming have a worse chance of survival. If genetic code creates a poor quality flipper, this penguin likely will not survive. However, if genetic codes randomly combine to create an effective flipper, this penguin will survive to pass on its own genetic material.

Over time, together, these forces help create natural selection. Natural selection allows species that are poorly adapted to survival to die off. However, species that are strong and able to adapt to the environment survive. Over time, there is a tendency towards creating stronger species. However, it is important to recognize that the environment may change as well. As the environment changes, new traits may be needed. The species will either develop these new traits through successive generations or it will die. For instance, the ancestors of penguins that flew would starve in the South Pole. The ones that could swim could obtain food and live.