bilights of mannera 1

Newbold

The Four Primary Mechanisms of Evolutionary Change
While natural selection is the principal engine of adaptation, modern evolutionary synthesis recognizes that it is one of four primary mechanisms that can alter the frequency of alleles (gene variants) in a population’s gene pool.
Natural Selection: As detailed above, this is the only mechanism that consistently leads to adaptation, as it non-randomly favors traits that enhance survival and reproduction. It can be further categorized based on the type of selective pressure. For example, sexual selection is a potent form driven by competition for mates, often resulting in elaborate traits like the peacock’s tail, which may not aid survival but significantly increases reproductive success.
Mutation: Mutation is the ultimate source of all new genetic variation. It refers to random changes in an organism’s DNA sequence that can arise from copying errors during cell division or from environmental damage. Mutations can be beneficial, neutral, or harmful. While a single mutation may have a large effect, much of evolutionary change is built upon the accumulation of many mutations with small effects. Without mutation, the well of genetic diversity would run dry, halting evolution.
Genetic Drift: In contrast to the non-random nature of selection, genetic drift refers to random fluctuations in allele frequencies from one generation to the next due to chance events. Its effects are most pronounced in small populations. By pure chance, an individual with a beneficial trait might fail to reproduce, or a mildly harmful allele might become more common. Drift is a non-adaptive evolutionary force that can lead to the loss of genetic variation and the fixation of alleles regardless of their fitness consequences.
Gene Flow: Also known as migration, gene flow is the movement of genes from one population to another. It can introduce new alleles into a population, thereby increasing its genetic variation and adaptive potential. Conversely, it can also make geographically separate populations more genetically similar, potentially counteracting the effects of local adaptation if the incoming genes are not suited to the new environment.