4B - Genetic diversity and natural selection Flashcards
What does it mean for genetic diversity of there are lots of different alleles?
High genetic diversity.
What is genetic diversity?
The number of different alleles of genes in a species or population.
What is genetic diversity within a population increased by?
- Mutations in the DNA (forming new alleles).
- Different alleles being introduced into a population when individuals from another population migrate into them and reproduce. This is known as gene flow.
What is gene flow?
When different alleles being introduced into a population when individuals from another population migrate into them and reproduce so the genetic diversity within the population is increased.
What allows natural selection to occur?
Gene diversity.
What causes a reduction in genetic diversity?
Genetic bottlenecks.
What is a genetic bottleneck?
An event that causes a big reduction in a population, e.g. when a large number of organisms within a population die before reproducing. This causes a reduction in the number of different alleles in the gene pool and so reduces genetic diversity.
How do genetic bottlenecks affect genetic diversity?
Causes a reduction in it.
What is a gene pool?
The complete range of alleles in a population.
What is the founder effect a type of?
Genetic bottleneck.
What is the founder effect?
Describes what happens when just a few organisms from a population start a new colony and there are only a small number of different alleles in the initial gene pool.
How might the frequency of each allele in the new colony made as a result of the founder effect differ from the original population and what effect might this have?
Might be very different to the frequency of those alleles in the original population - for example, an allele that was rare in the original population might be more common in the new colony. This might lead to a higher incidence of genetic disease.
Why might the founder effect occur?
As a result of migration leading to geographical separation or if a new colony is separated from the original population for another reason, such as religion.
What does natural selection do for the advantageous alleles in a population?
Increases them.
Describe the process of natural selection
Not all individuals are as likely to reproduce as each other. There’s differential reproductive success in a population - individuals that have an allele that increases their chance of survival are more likely to survive, reproduce and pass on their genes (including the beneficial allele), than individuals with different alleles.
This means that a greater proportion of the next generation inherits the beneficial allele.
They, in turn, are more likely to survive, reproduce and pass on their genes.
So the frequency of the beneficial allele increases from generation to generation.
Over generations this leads to evolution as the advantageous alleles become more common in the population.
