A4 - Gene Pools, Selection + Speciation

Process where organisms that are better adapted to their environment survive and reproduce in greater number, increasing the frequency of the advantageous allele within the population

Something that causes selection of an advantageous allele

Variation due to genetic mutation
Intraspecific
Competition
Reproduce more
Advantageous allele frequency increases
More generations = increased frequency

Directional
Stabilising
Disruptive

Favours extremes
Due to change in environment

Envrionemt is stable
Favours average

Favours extremes
Due to change in environment

Evolution of new species from existing species

Natural selection changes frequency of alleles
Undergo reproductive isolation to become genetically distinct

Allopatric
Sympatric

Speciation where biological populations are geographically isolated by a barrier and evolve genetic reproductive success

Biological populations are not geographically isolated
Mutation causes reproductive isolation

Change in allele frequency in small populations

Founder effect
Genetic bottleneck

Small numer of population are isolated from the main group and colonise another area
Due to migration and geographical isolation
Increased allele frequency
Reduced genetic diversity

Event occurs which drastically reduces population size
Reduces genetic diversity
Survivors form a much smaller group than before
E.g. hunting, earthquake, disease

Total sum of all alleles of all genes in a population

p$2$ + 2pq + q$2$ = 1
p + q = 1

p = dominant
q = recessive

p$2$ = homozygous dominant
pq = heterozygous
q$2$ = homozygous recessive