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What is a species?

 Species is among the basic taxonomical ranks and classification units in biology. Species is the largest group of organisms that is able to interbreed freely in nature and produce fertile offspring. It is a subgenus or division on a genus made up individuals that are related (Darwin & Quammen, 2008). Individuals in a particular species usually have same qualities or characteristics that are distinct from others in a different species. Individuals in a particular species can not breed with those from another species. A species is therefore considered to be the largest gene pool possible within the natural conditions.

What do genes have to do with evolution?

A gene is not only a single DNA unit but it is a replica of a particular type of DNA that is found all over the world. Evolution in organisms is as a result of a differential survival of genes that are competing leading to an increase in the frequency of alleles that have a phenotypic effect that promotes their own propagation successfully. Genetic variations lead to the basic evolutionary changes that are observed (Darwin & Quammen, 2008). Genetic variations are as a result of three primary factors. The first factor is mutations which cause changes on the DNA and when these changes accumulate they lead to an evolutionary change. The second factor is gene flow which is the movement of genes from a single population to another leading to genetic variations. The third factor is sex whereby it induces a new genetic combination in a population. This genetic shuffling brings about genetic variation leading to evolution.

How does natural selection work?

Natural selection involves the process through which life forms having traits which enable them to different pressures in the environment such as climate change, predators, and competition. These life forms end up surviving and reproducing in great numbers compared to similar species hence ensuring that these favorable traits are carried to the next generation (Freedman, 2006). Natural selection is a major contributor to evolution. Natural selection works when there is an existing variation in traits within a species. This is followed by a differential reproduction whereby the environment is unable to support the unlimited growth in population hence not all the individuals are capable of reproducing to their maximum potential. This leads to heredity whereby only individuals with a desired genetic basis survive (Freedman, 2006). The trait that is more advantageous becomes more common. If this process continues, all the individuals within the population will bear this desirable characteristic.

How can the evolution of one species affect the evolution of another?

There is no single species that exists in a vacuum and hence different forms of life freely interact in the physical environment. Therefore, the evolution of a species ends up influencing that of another species which it coexists (Darwin & Quammen, 2008). This is caused by a change in the natural selection pressures faced by these species. This leads to a co-evolution if the species have ecological relationships such as predator/prey, mutualistic and competitive species.

Does evolution stop once a species has become a species?

Evolution does not stop when a species becomes a species. Populations of living organisms continuously go through evolution, though the speed and degree of the process differs from group to group. Those populations that undergo major environmental changes evolve more quickly compared to those within stable conditions. There are also continuous variations in populations caused by mutation, random fertilization and crossing over. Selection can be stabilizing in stable environments but alleles still change. Evolution and speciation go hand in hand (Freedman, 2006).

References

Darwin, C., & Quammen, D. (2008). On the origin of species (Illustrated ed.). New York: Sterling.

Freedman, D. (2006). Natural selection. New York: Hyperion.