Genetic Diversity

Genetic diversity: Discuss the issues related to genetic diversity: mutations, sexual reproduction, migration, and population size. Under most circumstances, when "an individual possesses a trait or traits that allow it to compete better for food, shelter, mates, and nesting sites, then that individual will produce more offspring because it is better nourished, is better protected, lives longer and has mate(s) with which to reproduce more offspring" (Furr n.d.).

Thus, if a species produces a spontaneous mutation which is beneficial for the species' survival, the mutated organism will live, grow, and reproduce and pass on the mutation to successive generations. The mutation may survive as a heterogeneous allele, but if the mutation is common enough or the mutation produces enough offspring, eventually the useful mutation will manifest itself in greater and greater numbers in the population. "Sexual reproduction allows the genetic information of two parents to recombine to form a new individual.

One great advantage, from the population biology point-of-view, is that sexual reproduction produces a great deal of genetic variation through the shuffling of both beneficial and deleterious mutations" (Hardin, Bertoni & Kleinsmith 2012). One classic example of this can be found in peppered moths in Manchester, England. "As soot from coal-fired factories blackened trees and buildings in 19th-century England, naturalists noticed that peppered moths were also trading in their light-colored wings sprinkled with black specks for a sleek, all-black stealth-bomber look known as the carbonaria form.

Within a few decades of their first appearance near Manchester, the black moths dominated, making up 90% or more of the peppered moth population in local urban areas… once the air was cleaned up in Britain, the black moths declined in numbers while the peppered form increased." (Saey 2011). The peppered moths once had more advantageous camouflage in nature and were the norm, but as coal dust covered the industrialized city, the mutated black survived and passed on these genes to the next generation, fundamentally changing the character of the population's color.

Genetic migration can also substantially increase the genetic diversity in a given population. Migration refers to "the movement of alleles between populations" (Chapter 6, n.d., Buffalo State). Alleles are dispersed either though the movement and mating of adult animals and through "seeds and spores of plants, planktonic larvae of intertidal animals, gametes/zygotes of algae, etc." (Chapter 6, n.d., Buffalo State). The movement of new organisms into the population that can mate with other organisms facilitates the creation of greater genetic diversity.

Unlike spontaneous mutations, genetic migration has its origins in the movement of organisms outside of the population into the population. For favorable traits that are supported by the environment: "If selection and migration tend to increase the frequencies of the same alleles, selection can amplify effect of migration" (Chapter 6, n.d., Buffalo State). But if the new traits are not supported by the needs of the environment "selection is stronger than migration, than differences among populations will be maintained, even in the face of migration" (Chapter 6, n.d., Buffalo State).

Genetic drift, however, can cause populations to become less, rather than more heterogeneous. "In each generation, some individuals may, just by chance, leave behind a few more descendants (and genes, of course!) than other individuals. The genes of the next generation will be the genes of the 'lucky' individuals, not necessarily the healthier or 'better' individuals" (Genetic drift, n.d., Evolution 101). While genetic drift can manifest itself in all populations, it is.