Ch18 Populations and evolution Flashcards
1
Q
Gene pool
A
Combination of all the genes present in a population
2
Q
Hardy Weinberg assumptions
A
- no mutations
- population is isolated
- no selection occurs
- large population
- random mating
- no immigration/ emmigration
3
Q
Hardy Weinberg principle
A
proportion of dominant:recessive
remains constant in population
over generations
4
Q
HW phenotype equation
A
p+q=1
5
Q
HW genotype equation
A
P^2 + q^2 + 2pq = 1
6
Q
Allopatric speciation
A
- mutation causes variation
- reproductive isolation/ no interbreeding
3. - change in allele frequency
- Unable to reproduce to produce fertile offspring
7
Q
Sympatric speciation
A
- Geographical isolation
- No interbreeding- separate gene pools
- variation due to mutation
- different selection pressures
- different reproductive success - pass on alleles to offspring
- change in allele frequency
- unable to reproduce to produce fertile offspring
8
Q
Directional selection
A
- occurs in changing environment
- selection against one extreme
- mean is shifted towards favoured extreme
9
Q
Stabilising selection
A
- occurs in unchanging environment
- selection against extreme phenotypes
- standard deviation reduced
- mean unaltered(best adapted)
- repeated over many generations
- increased proportion of mean phenotype
10
Q
Small population
A
- smaller gene pool
- less variation
11
Q
Natural selection
A
- variation present
- certain phenotype more likely to survive and reproduce
- pass on alleles to offspring
- change in allele frequency
12
Q
Disruptive selection
A
- occurs in changing environment
- selection against mean phenotype
- mean shifts towards both extreme phenotypes
13
Q
Reasons for allopatric speciation
A
- behavioural - different courtship displays
- temporal- different breeding/feeding times
- mechanical - reproductive incompatibility
14
Q
Genetic drift
A
Change in the frequency of a gene variant due to random chance in a population
