Question

imagine two populations of equal size; one with low levels of genetic variation, and the other with high levels of genetic variation. Which population would be less likely to adapt to its environment by natural selection? Provide a biological rationale for your response.

Answer 1

Answer: Population with low levels of genetic variation.

Explanation:

Genetic variability is a measure of the tendency of a population's genotypes to differentiate. Individuals within a species are not identical and while they are recognisable as belonging to the same species, there are many differences in their form, function and behaviour. In each of the characteristics that we can name of an organism there will be variations within the species

So, genetic variability refers to the diversity in gene frequencies.  It can refer to differences between individuals or differences between populations. Mutations are the fundamental cause of genetic variability, but mechanisms such as sexual reproduction and genetic drift also contribute to it.

So, the two main sources of genetic variation are mutations and the combination of genes that result from sexual reproduction:

• Mutations: A mutation is any change in a DNA sequence. It can be due to errors in DNA replication, radiation or environmental chemicals. In many mutations, they affect the phenotype. Some even affect the biological efficiency of an organism or the ability to survive and reproduce in its environment. Other mutations may not affect biological efficacy.1

• Combination of genes from sexual reproduction: Most hereditary differences are due to the combination of genes that occurs during gamete reproduction. Each chromosome of a homologous pair moves independently during meiosis. Therefore, the 23 pairs of chromosomes that humans have can reproduce 8.4 million gene combinations, all different. Also during meiosis another process occurs, the crossing over which increases the number of different genotypes that can appear in the offspring. When the alleles recombine during sexual reproduction, they can reproduce very different phenotypes. Therefore, sexual reproduction is an important source of variation in many populations.

When a population has greater genetic variability, the individuals in that population will have more genes needed to adapt to different adverse situations and survive and reproduce. For example, in an inhospitable environment where there are many predators, only the strongest and fastest individuals will survive. And if there is a great deal of genetic variability in the population, it is more likely that there will be more individuals with the necessary genes to do so. In addition, those more adapted individuals will reproduce and leave equally or more adapted offspring, due to the combination of genes through sexual reproduction. Also, these populations are characterized by a high rate of beneficial mutations, which provides benefits for survival.

Natural selection is an evolutionary phenomenon that is defined as the differential reproduction of the genotypes of a biological population. The classic formulation of natural selection establishes that the conditions of an environment favour or hinder, that is, they select the reproduction of living organisms according to their peculiarities. This explanation is based on three premises; the first is that the trait subject to selection must be inheritable. The second holds that there must be variability in the trait among individuals in a population. The third premise argues that the variability of the trait must result in differences in survival or reproductive success, making some newly-emerging traits likely to spread in the population. The accumulation of these changes over generations would produce all the evolutionary phenomena.

The result of the repetition of this scheme over time is the evolution of the species.