Evolution: HWE + Evolutionary mechanisms Flashcards
What is the purpose of Hardy- Weinberg EQB
calculates expected genotypic frequencies in EQB
1) observed matches expected (calculates) = NO evolution
2) observes doesn’t match expected = evolution has occurred
*acts as a null hypothesis
assumptions of HWE
1) population is ∞ large
‘Ramen needs more MSG’
Ramen - Random mating Needs - No More - Mutation M - Migration (geneflow) S - selection G - genetic drift
1) p^2 +2pq+q^2 = 1
2) p+q= 1
what do the variable in each equation represent?
what is the difference between the equations?
- p and q = frequency of dominant and recessive ALLELES
- p^2, 2pq, q^2 = genotype frequencies
- p^2 = AA (homozygous dominant)
- 2pq = Aa (heterozygous)
- q^2 = aa (homozygous reccesive)
p^2 +2pq+q^2 = 1 : calculates GENOTYPIC frequencies
p+q = 1 : calculates ALLELE frequencies
Steps to solve HWE problems
1) calculate observed genotype frequencies
2) calculate observed allele frequencies
3) calculate expected genotype frequencies (using observed genotype frequencies)
4) compare observed with expected
macroevolution
large scale evolution
descent of different individuals from a common ancestor over a long period of time
microevolution
changes in allele frequency in a population over generations (short period of time)
fitness
the relative ability of individuals to produce viable offspring
adaptations
a heritable trait that increased an individual’s ability to survive and reproduce compared to those without that trait.
trait must be:
- heritable
- functional
- affect fitness
evidence of change (evolution) through time
1) transitional fossils
2) vestigial structures: have little to no function but are similar to the functioning structure in a closely related species
* *ie) human appendix
homology
the similarity between species that result from inheriting traits from a common ancestor.
**homologous when all species in a monophyletic group have it
3 types:
1) structural: similar adult morphology
2) developmental: similarity in embryonic form
3) genetic: similar DNA, RNA or amino acid sequence
What are the (4) evolutionary mechanisms?
1) mutations
2) natural selection
3) gene flow
4) genetic drift
Mutations
change in OG DNA sequence Occur randomly Create variations and new phenotypes rare ****aren't strong enough to act along
Natural selection
- individuals with a certain trait make them more fit
- individuals with beneficial alleles carry them to the next generation while less favourable alleles are filtered out
- can arise from adaptations
REQUIREMENTS:
- variation
- heritability
- variation must have a diff in fitness (evolutionary association )
Types of Natural selection
1) Ecological
a) Stabilizing selection:
- favours intermediate phenotypes (eliminate extremes)
- Averae starts the same
- reduced variation
b) Directional
- favours one extreme phenotype
- changes average trait values
- reduced variation/diversity
c) Disruptive
- favours both extremes
- average value stays the same
- increase variation/diversity
2) sexual: non-random nation. females determine which alleles get passes on
a) intrasexual: competition for mates (male-male interactions)
b) intersexual: (female) mate choice
3) Artificial: humans choose which alleles get inherited to the next generation
ie) bananas
Gene flow
movement of individuals or gametes IN AND OUT of a population
- = > genetic variation
- homogenized over time
