APBIO 7.3

Microevolution

changes/fluctuations in allele frequencies in a population overtime

• bottleneck effect

• genetic drift, flow etc.

• founder effect

Macroevolution

signficiant changes

population

able to interbred and reproduce healthy, fertile offspring

Gene pool

all alleles of all genes in the population

fixed loci/locus

when all members of the population are the same type of homozygous (ex. all AA or all aa)

Conditions for Hardy-Weinberg Equilibrium

1. No mutations 

2. Random mating 

3. No natural selection 

4. Extremely large population size

5. No gene flow

how do allele frequencies change/micrevolution

• mutations

• Natural selection

• Genetic drift

  • Founder effect

  • Bottleneck effect

• Gene flow

genetic drift

smaller populations are more affected

occurs by chance (ex. human steps on more green than brown bug)

often loose more alleles of 1 type than the other, reducing genetic diversity

founder effect

The founder effect occurs when a few individuals become isolated from a larger population and may develop different alleles

ex. red bug moves from green-red bug land to just red bug land

bottleneck effect

Diverse group → many die/gone → survivors repopulate and change the frequency of certain alleles

genetic flow

movement of alleles, most often via individuals moving ; may cause better/worse fitness because good/bad alleles may be introduced

decreases the differences between populations overtime

relative fitness

contribution an individual makes to the gene pool of the next generation in comparison to other individuals

directional selection

one extreme is being favoured/slowly achieved

disruptive selection

both extremes are being favoured

stabilizing selection

not much change, “middle ground” is favoured

sexual selection

natural selection concerning sexual success

can cause sexual dimorphism

sexual dimorphism

the female and male are different in terms of behavior, looks, etc. for example female birds are boring while male birds are fancy and colorful

intrasexual selection

competition between (usually male) birds for females

females are picky leading to a type of natural selection

good genes hypothesis

allows for those with good genes to be favoured by natural selection

mate choice

the more fancy a male bird the more sexual success but fitness is lowered because easier for predators to find them

genetic variation is preserved how

heterozygote advantage, frequency dependent selection, environment, natural selection etc etc.

frequency-dependent selectin

a phenotype declines if it is too common in a population