Genetic Diversity: Mutations, Sexual Reproduction, Migration, and Population Size
The Four Factors
Genetic diversity is the variation in the characteristics inherited from the parent organisms in a population of a specific species. This diversity is extremely important for the survival of a species as it allows for the survival of certain members when a portion of the group is destroyed either through disease, changing environments, or other factors that are detrimental to their survival. Genetic diversity can come about through a number of ways, including: mutations, sexual reproduction, migration, and variations in population size.
Mutations are changes in the alleles that introduce new genetic information into a group. There are two types of mutations: hereditary and acquired. Hereditary mutations are those inherited from the parents and are present in the offspring its entire life. Acquired mutations (also called somatic mutations) are those that happen due to outside circumstances during the life of the offspring. These are usually the result of environmental influences such as exposure to ultraviolet rays or chemicals. Some mutations are readily visible. These include such atrocities as two-headed snakes, five-legged sheep, frogs with six-eyes, etc. Many other mutations are not so obvious. An organism that is susceptible to a certain disease, for example. While mutations will introduce new characteristics into a population, these changes are almost always harmful, and usually lead to death in a species, not to an improvement.
Sexual reproduction, unlike mutations, does not cause the creation of new alleles, but rather combines different alleles from the parent organisms to introduce new combinations of alleles. If an organism receives a combination of alleles that cause it to be more likely to survive than others in its community, then it will be better able to produce offspring. This next generation will, in turn, inherit these genes and then pass them on to their offspring. The main advantages of sexual reproduction over asexual reproduction, as stated by the Journal of Evolutionary Philosophy, is this ability to combine genes from different organisms because now “beneficial mutations from separate ancestries can be combined, beneficial mutations can be separated from harmful mutations, and unsuccessful genetic traits can easily disappear from an existing population.”
Migration occurs within all major branches in the animal kingdom. These migrations are beneficial to the survival and breeding of the migrating animals. One advantage of these migrations is that it allows them to come into contact with others of their own species. As these different groups meet and interact, they also begin to breed with each other. Certain alleles that are absent in one group are generally present in the other group. Many times these missing genes are important to the survival of the species. As the two groups begin to interbreed, these missing genes now become a part of the genetic makeup of the species. Interbreeding in turn also allows for the combinations of beneficial characteristics that would otherwise never occur within a single group.
Another factor that can contribute to the genetic diversity, or lack there of, is the size of the population. Obviously, the larger a population, the greater diversity there will be. The problem with a smaller population is not only the extreme lack of diversity, but also the fact that genes that are in a community can be lost over time. One way this happens is through what is called genetic drift. Genetic drift occurs whenever a small portion of a group carries a certain gene. If every organism that carries this gene fails to produce offspring, whether it is through an early death or the inability to find a mate, this gene will be lost forever. This is especially detrimental to a species if this characteristic is important to the survival of this particular species.
Genetic diversity is what allows a species to survive. As environments, populations, and circumstances change, so too must a species adapt to these changes. The greater genetic diversity there is in a group, the better able it is to pass on beneficial genes to their offspring. Even as certain characteristics lie dormant, they are still a part of the makeup of the species, and thus are there when needed if environment or certain situations call for them.
© 2018 Stephen Moore