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by kristinkage
Last updated 6 years ago

Evolutionary Biology

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Gene Pool, Genetic Drift and Bottleneck Effect

The gene pool is a set of genes for a species. It usually applies to individuals in a species. Genetic drift happens mostly by chance. It happens when alleles increase and decrease over time due to random events. The bottleneck effect occurs when the population has been reduced for at least one generation. It reduces the genetic variation by a lot.

Changes in Gene Frequency

Lots of things can affect the gene frequency. Non-random mating can change gene frequency. This is when humans choose mates for organisms, so it's not random. People might do this so better traits and alleles are passed on to make a species better. Mutations can also affect gene frequency. Mutations are random, and are a change in an organism's DNA. It can help an organism, or it can be harmful. Genetic drift also changes gene frequency, because it is a change in alleles due to random events. Natural selection is another way to change gene frequency. This is when organisms mate with other organisms that are best fit for their environment. For example, if there are black moths and white moths in a dark forest, predators could easily find the white moths. The black moths would then mate with each other to produce more black moths. This changes the gene frequency in moths. Gene flow is any movement of individuals or gene from one population to another. This changes the gene frequency because new genes are being introduced.

Reproductive Isolation

Tons of organisms are islotated from each other so they can't reproduce. Allopatric speciation is one form of isolation. This happens when a species is seperated by a large distance or physical feature, like a river or mountain. This keeps at least two groups from mating regularly. This is similar to geographic isolation, but allopatric speciation happens as a result from geographic isolation. Sympatric speciation is when part of a species evolves without the other part. This happens while the species live in the same place. Behavorial isolation is when organisms act a certain way to attract mates. Certain birds have certain calls to attract other birds. Other birds, not of the same species, won't respond to the calls. This keeps the different species isolated. Temporal isolation are species with different breeding seasons. For example, some frogs breed during the winter, and others breed during the spring. Because they don't breed during the same season, they are isloated and won't mate. Hybridization is when two different species mate to create a new species that is isolated from the parent species. The new species then can't create a steady population.


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