Evolution may lead to speciation Flashcards
(9 cards)
What is disruptive selection?
Disruptive selection is where individuals with alleles for characteristics of both extremes at either end of the range are more likely to survive and reproduce. So the mean stays the same but it becomes less common due to greater standard deviation.
What is meant by selection pressure?
Selection pressure is the ability to avoid predators.
What is evolution?
Evolution is the change in allele frequencies in a population
What is speciation?
Speciation is the idea that new species develop from a common ancestor.
How does speciation happen?
1) Part of the population becomes separated from the others, and so becomes reproductively isolated.
2) Each population finds itself in a different environment, and so experiences different selection pressures.
3) Natural selection occurs, and different alleles are of an advantage in the different populations.
4) Allele frequencies change in the two gene pools.
5) Eventually, the two populations are so genetically different that they can no longer interbreed to produce fertile offspring, they become two different species.
What are the two types of speciation?
Allopatric, and sympatric.
How can reproductive isolation occur?
Allopatric speciation where there is physical reproductive isolation (e.g. species becomes separated by a river or mountain range). Sympatric speciation where populations don’t become physically separated but there’s some other reason for reproductive isolation (behavioural, temporal, mechanical)
What is meant by genetic drift?
Evolution can occur by natural selection or by genetic drift where allele frequencies change due to chance due to not every individual becoming a parent or having the same number of offspring.
What impact does genetic drift have on smaller populations?
Genetic drift has a greater impact on smaller populations because each individual makes up a greater proportion of the population meaning there’s a greater chance that one individual is the sole owner of one allele. If this individual were to die out, this has a much greater effect on the population than if many more members of the population shared this same allele.
