Gene Pools Flashcards
What is a gene pool?
The sum of all the alleles in a gene pool
List the factors that increase the range of alleles in a gene pool
Mutations Immigration (type of gene flow)
Explain how mutations increase the range of alleles in a gene pool
Mutations create new alleles and therefore new phenotypes
If the new phenotype makes the individual more adapted at carrying out their niche, they are more likely to survive, reproduce and pass the mutant allele to their offspring
Over time the new mutant allele becomes more common in the gene pool
Explain how immigration/gene flow increases the range of alleles on a population
As an individual arrives into a population, they may carry an allele that wasn’t originally present in the gene pool.
If this allele makes the individual more adapted at carrying out their niche, they are more likely to survive, reproduce and pass the new allele to their offspring
Over time the new allele becomes more common in the gene pool
List the factors that decrease the range of alleles in a population
Bottleneck effect (type of genetic drift) Founder effect (type of genetic drift) Genetic drift Emigration (type of gene flow) Natural selection
Define genetic drift and explain how it decreases the range of alleles in a population’s gene pool
The random loss of alleles from a population.
As an individual is lost from a population due to a random event, it may have been the only individual who carried a certain allele. This allele is then lost from the gene pool decreasing the allele range. Particularly true for small populations because in a larger population there is a greater chance that another individual carried that allele
Define bottleneck and explain how it decreases the range of alleles in a population’s gene pool
When a population decreases quickly in size due to environmental change. As individuals are lost from the population, the alleles that they carry are also lost form the gene pool decreasing the range. The population that survives a bottleneck will have less genetic variation than prior to the environmental change
Define founder and explain how it decreases the range of alleles in a population’s gene pool
When a limited number of individuals from a population leave and establish a new population that is reproductively isolated from the larger original population. Because it originated from only a few individuals, there is a smaller range of alleles compared to the original population and the gene pool of the founding popuplation tends to reflect the alleles of the ‘founders’
Define emigration and explain how it decreases the range of alleles in a population’s gene pool
Emigration is a type of gene pool where individuals leave a population and join another. This decreases the range of alleles in that gene pool, especially if it is a small population, because that individual may have been the only one to have that allele
Define natural selection
Individuals within a population have phenotypes that make them more likely to survive and reproduce
What are three types of natural selection?
Stabilising selection
Directional selection
Disruptive selection
Explain how natural selection affects gene pools
Individuals within a population have phenotypes that make them more likely to survive and reproduce. Those alleles that give those ‘beneficial’ phenotypes are more likely to be passed on to the offspring. Individuals with phenotypes that make them less adapted to a changing environment are less likely to survive and/or reproduce. Therefore those less beneficial alleles are less likely to be passed on to offspring. Over time the beneficial alleles become more common in the gene pool and the less beneficial alleles become less beneficial.
Why is natural selection of benefit to a species?
Beneficial alleles are becoming more common in the gene pool so the population is more adapted to the environment it is living in.
