Quick questions on Gene pools and allele frequency change: WACE Year 12 Biology

A gene pool is the total collection of alleles present in all the individuals of a population. Evolution can be described as a change in the allele frequencies of a gene pool over time. Natural selection is one cause of such change, but several other processes also shift allele frequencies, sometimes without any survival advantage being involved.

Genetic drift is random change in allele frequencies from one generation to the next due to chance alone. Because real populations are finite, not every allele is passed on in exact proportion. By chance, some alleles become more common and others rarer, and rare alleles can be lost entirely.

Gene flow is the movement of alleles between populations when individuals migrate and breed, or when pollen or seeds are carried between plant populations. Gene flow tends to make populations more genetically similar and introduces new alleles into a population. A barrier that stops gene flow, such as a mountain range or ocean, allows populations to diverge.

A bottleneck occurs when a population crashes sharply, for example through disease, drought or hunting, leaving only a small number of survivors. The survivors carry only a fraction of the original genetic diversity, often not a representative sample. Even if the population recovers in numbers, its genetic diversity stays low. Reduced diversity leaves a population less able to adapt to future change.