8.2 Gene Pools

population

a breeding group of individuals of the same species occupying a particular habitat and a particular niche

gene pool

the sum total of all the genes in a population at a given time

Hardy-Weinberg equilibrium

the mathematical relationship between the frequencies of alleles and genotypes in a population. The equation used to describe this relationship can be used to work out the stable allele frequencies within a population

Gene flow

the migration of either whole organisms or genetic material into or out of a population and into another population, tending to make different populations more alike, but changing the allele frequencies within each individual population all the time

population bottleneck

the effect of an event or series of events that dramatically reduces the size of a population and causes a severe decrease in the gene pool of the population, resulting in large changes in allele frequencies and a reduction in genetic diversity

founder effect

the loss of genetic variation that occurs when a small number of individuals become isolated, forming a new population with allele frequencies not representative of the original population (aka. voluntary bottleneck)

stabilising selection

the natural selection acting to conserve what is already present in a population, reducing variation in a population, so that the frequency of some alleles is very high but other alleles are greatly reduced.

directional selection

the 'classic' natural selection that occurs whenever environmental pressure is applied to a population, showing a change from one phenotypic property to a new one more advantageous in the circumstances

disruptive/diversifying selection

gives an increase in the diversity of the population rather than a trend in one particular direction. It is common when conditions are diverse and small subpopulations evolve different phenotypes suited to their very particular surroundings, and often results in the evolution of new species

genetic drift

random changes in the gene pool of a population that occur by chance not because they confer any advantage or disadvantage on the offspring