M6 S3 : Evolution Flashcards
What is a gene pool?
The complete range of alleles present in a population.
What is allele frequency?
How often an allele occurs in a population. It is usually given as a percentage of the total population.
What is a population?
A group of organisms of the same species living in a particular area.
What is a selection pressure?
Anything that affects an organisms chance of survival and reproduction.
What is evolution?
When the frequency of an allele in a population changes over time.
What is the breeding population?
The animals that are surviving, reproducing and passing on their alleles.
What is stabilising selection?
When the environment is not changing much, individuals with the alleles for characteristics towards the middle of the range are more likely to survive and reproduce.
What is directional selection?
When there is a change in the environment, individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce.
What is evolution by genetic drift?
Chance dictates which alleles are passed on. It has a greater effect in smaller populations where chance has a greater influence.
What is a gene pool?
The complete range of alleles in a population.
What is a genetic bottleneck?
An event (like a natural disaster, disease and human destruction) that causes a big reduction in a population’s size, leading to a reduction in the gene pool.
What is the founder effect?
Describes what happens when just a few organisms from a population start a new population and there are only a small number of different alleles in the initial gene pool.
What is gene flow?
The introduction of new alleles from the outside population
What are some reasons that the founder effect occurs
- Migration leading to geographical separation.
- A new colony separates from original population due to religion.
What is the Hardy-Weinberg principle?
A mathematical model that predicts that the frequencies of alleles in a population will not change from one generation to the next.
What conditions is the Hardy-Weinberg principle true?
- It has to be a large population where there is no immigration, emigration, mutations or natural selection.
- There needs to be random mating, all possible genotypes can breed with all others.
What is the allele frequency equation?
p + q = 1
p = frequency of the dominant allele.
q = frequency of the recessive allele.
Why does the allele frequency equation add to 1?
They add to 1 because the total frequency of all the possible alleles for a characteristic in a certain population add to 1.
What is the equation for genotype frequency?
p^2 + 2pq + q^2 = 1
p^2 = frequency of homozygous dominant genotype.
2pq = frequency of heterozygous genotype.
q^2 = frequency of homozygous recessive genotype.
Why does the genotype frequency equation add to 1?
The total frequency of all the possible genotypes for one characteristic in a certain population is 1, so frequencies of each of the individual genotypes must add to 1.
What is artificial selection?
When humans select individuals in a population to breed together to get desired traits.
What can artificial selection also be called?
Selective breeding.
What are the problems with artificial selection?
- Reduces the gene pool.
- Causes problems with the organism.
What is a species?
A group of similar organisms that can reproduce to give fertile offspring.
What is speciation?
The development of a new species.
What is allopatric speciation?
When populations become reproductively isolated due to a combination of geographical isolation and natural selection.
How does reproductive isolation occur?
The changes in alleles and phenotypes of 2 populations prevent them from successfully breeding together. These changes include :
- Seasonal changes : Individuals of same population develop different flowering or mating seasons, or become sexually active at different times of year.
- Mechanical changes : changes in genitalia prevent successful mating.
- Behavioural changes : A group of individuals develop courtship rituals that are not attractive to main population.
What is Sympatric speciation?
Speciation without geographical isolation.
What is reproductive isolation?
When populations of the same species can no longer breed together to produce fertile offspring (as a result of changes in allele frequency).
What is geographic isolation?
When a physical barrier divides 2 populations of a species.
