10.3 Gene pools and speciation Flashcards
What is a gene pool?
A gene pool consists of all the genes and their different alleles present in an interbreeding population.
What are the patterns of natural selection?
Stabilising selection, disruptive selection or directional selection.
What is stabilising selection?
In stabilising selection selection pressures act to remove extreme varieties. For example, average birth weights of human babies are favoured over low birth weight or high birth weight. A medium sized is favoured.
What is disruptive natural selection?
In disruptive natural selection, selection pressures act to remove intermediate varieties, favouring the extremes.
What is directional selection?
The population changes as one extreme of a range of variation is better adapted.
What are the different types of reproductive isolation?
Temporal, behavioural or geographic
What is temporal isolation?
This is when there is isolation between the gene pools in the same area is caused by different species mating at different times.
What is speciation?
The formation of a new species by the splitting of an existing population from that of another population.
What is behavioural isolation?
If isolation of gene pools occurs in the same area. If speciation occurs, then the process is termed sympatric speciation. For example, behaviour can be behavioural if closely related individuals differ in courtship behaviours then they are often only successful in attracting members of their own population. SO THE GENE POOLS DO NOT MIX
What is geographic isolation?
When gene pools are separated by physical barriers or distance. This speciation is called allopatric speciation.
What is sympatric speciation?
When speciation occurs in the same geographic location, for example because of behaviour.
What is allopatric speciation?
Speciation that occurs because of geographical reasons.
What is gradualism?
Gradualism is the idea that species slowly change through a series of intermediate forms. It was the early framework but was confronted by gaps in the fossil record e.g. absence of intermediate forms.
What is punctuated equilibrium?
The idea that speciation can occur rapidly and therefore the opposite of gradualism.
Punctuated equilibrium holds that long periods of relative stability in a species are “punctuated” by periods of rapid evolution. According to the theory of punctuated equilibrium, gaps in the fossil record might not be gaps at all.
What is a polyploid?
An organism that has more than two homologous chromosomes.
It can result from hybridisation events between different species or it can result from when chromosomes duplicate in preparation for meiosis but meiosis does not occur. When this diploid gamete fuses with a haploid you get one with three homologous chromosomes and it produces fertile offspring.
