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Topic 7

Speciation and genetic drift

TermDefinition
How does natural selection occur Competition for resources and impact of disease and predators
How does a wide range of phenotypes occur Genetic and enviromental impacts. Primary source is due to mutation meosis Random fusion of gametes
How does selection pressure occur Predation and disease
How does this happen Organisms with selective advantages more likely to survive. They also produce more offsprings and pass on their favourable alleles on to the next generation. The effect of this change is allele frequency
What are the 3 types of selection Stabilising Directional Disruptive
What is disruptive selection This is when individuals which contain the alleles coding for extreme trait are more likely to survive and pass on there alleles This results in the allele frequency changing and more individuals possess the allele for the extreme trait
Continued disruptive selection can lead to speciation
What is speciation The process results in the creation of new species
How can this happen This is when species become reproductively isolated. This isolation means that there is two populations of the same species however they cannot breed together
2 different ways species can be reproductively isolated Geographically (allopratic) Because of changes in reproductive mechanisms (sympatric)
Allopatric speciation Due to seperation different beneficial mutations occur. This leads to them being so genetically different that they would be unable to interbreed to create a fertile offspring
Sympatric Speciation Populations can become isolated due to a a random mutation which could impact reproductive behaviour as individuals may perform a different courtship ritual. As there is no gene flow over time this causes their DNA to be different so they cant breed.
What is genetic drift This is the change in the allele frequency within a population between generations. The smaller the population is the bigger the impact on allele frequency changes have proportionally
This is why smaller populations go through evoloution more often
Created by: yHya
 

 



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