3.0 KiB
Unit 3 (TBD) Evolution is change in the population, not individuals. When changes in allele frequency occur, ==microevolution== has occurred, which is the smallest scale of evolution. Microevolution can eventually lead to ==macroevolution==, which is the creation of new species.
Example begin:
In the Richmond Hill High School forest there lives a population of bunnies. Let B rep the allele for brown. Let b rep the allele for white. How many B? 3B/total 8 alleles How many b? 5b/total 8 alleles. Allele frequency of B is 0.375=p (represents allele frequency of dominant trait). Allele frequency for b is 0.625=q (represents allele frequency of recessive trait).
| Generation | B | p | b | q |
|---|---|---|---|---|
| 1-baseline | 14 | 14/44=0.318 | 30 | 30/44=0.682 |
| 2 | 11 | 11/44=0.25 | 33 | 33/44=0.75 |
| 3 | 16 | 16/44=0.364 | 28 | 28/44=0.636 |
| 4 | 15 | 15/44=0.341 | 29 | 29/44=0.659 |
| 5 | 15 | 15/44=0.341 | 29 | 29/44=0.659 |
| 6-climate change | 2 | 2/44=0.046 | 42 | 42/44=0.954 |
!
Microevolution has occured because allele frequency changed. From 0.318 to 0.409. Natural selection.
To check if a change is significant, use chi square.
Example concluded.
Hardy-Weinberg equation. If allele frequencies aren't changing, then the population is in ==Hardy-Weinberg== equilibrium (microevolution not occurring). If allele frequencies change, then microevolution occurs, which can be due to:
- Natural selection.
- Genetic drift.
- Gene flow.
- Mutation.
- Non random mating.
For Hardy-Weinberg equilibrium to occur, these conditions need to be met:
- No mutation, no alleles can arise.
- No migration, no new members and alleles can join/leave.
- Large gene pool.
- Random mating.
- No selection, natural selection doesn't favor one phenotype over the other. These 5 five things keep the population stable.
==Allele fixation== is when only one allele is present for a particular gene, allele frequency for one allele is 100%. It occurs more often in smaller populations.
!
Graph one represents Hardy Weinberg Equilibrium, graph 2 represents microevolution and graph 3 represents allele fixation.
p+q=1\\p^2+2pq+q^2=1 p^2 represents genotype frequency (homozygous dominant) while q^2 represents genotype frequency for homozygous recessive. 2pq represents genotype frequency of heterozygous.
Example 1: Black dominant white recessive, 263 black geese 413 white geese.
"what is genotypic frequency of the white geese"
Let B rep black feather.
Let b rep white feather.
bb=$q^2$=413/676=0.6109
"what is allele frequency of white allele"
b=$q^2$=\sqrt{0.6109}
=0.7816
"what is alele frequency of black allele"
1-0.7816=0.2184
"genotypic frequencies of homozygous black geese"e
p^2+2*0.2184*0.7816+0.6109=1
p^2=0.0477
==ALWAYS FIND RECESSIVE ALLELE FREQUENCY FIRST==
"heterozygous genotype frequency"
2pq=2(0.2184)(0.7816)
pq=0.3414
Example concluded.