Q23.4-2CC
Question
Explain why natural selection is the only evolutionary mechanism that consistently leads to adaptive evolution in a population.
Step-by-Step Solution
VerifiedNatural selection allows adaptation in a population by selecting only beneficial alleles. It increases the allele frequencies of heritable traits. The natural selection process decreases deleterious alleles by selecting against them, leading to adaptive evolution.
Darwin put forward the theory of natural selection. According to this theory, competition between organisms causes a struggle for their existence. In order to survive in nature, organisms undergo variation. The heritable variation in a population gets selected by nature, which leads to the survival of the fittest.
The fittest population denotes organisms with better adaptive features to survive in nature by increasing their progeny.
The evolution that gives rise to traits that help the population increase their progeny and survive in nature is called adaptive evolution. It allows the organism to withstand environmental changes. An increase in the frequency of beneficial alleles tends to form adaptive evolution.
For example, in humans, the ability to digest lactose is an adaptive evolution. The increase of frequency in lactase persistence alleles gave the ability to digest milk even in adulthood.
Natural selection does not act on any individual allele. It plays a significant role in the overall appearance of the organism for its better survival. Natural selection ensures that traits contributing to an increase in reproduction are passed down to the gene pool of the next generation.
Alleles of fecundity phenotype, which can put the existence of the population at risk, will not be passed down the next generation because an individual with a defected gene cannot survive to reach reproductive age. Thus, natural selection always leads to adaptive evolution in the population.