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- -shared derived traits between lineages
- -all synapomorphies are homologous but not all homologies are synapomorphies
ex. Mitochondria is a synapomorphy for all eukarya but not for humans/chimps
-Genetic code (DNA, RNA, ribosomes, transcription/translation, proteins)-metabolic pathways-membrane
- -Same trait in different group but it's not due to common ancestry
- ex. crocodile and hippopotamus have eyes on top of their head
Hardy Weinberg Assumptions
- -No Mutation
- -No Selection
- -No Migration
- -No chance events
- -Random Mating
- Violation of the assumptions results in evolution!
Hardy Weinberg Conclusions
1.) allele frequencies in a population will not change throughout generations
2.) if allele frequencies are given by p and q, then the genotype frequencies will be given by p2, 2pq, and q2.
Systematics vs Taxonomy
S: categorizing that reflects evolutionary history
- -the maintenance of 2 alleles in a population if each allele is advantageous when it is rare
- -fitness depends on the commonality of the genotype
- ex. elderflower orchids: the less common color has higher fitness because it recieves the most visits from pollinators.
- -heterozygotes have higher fitness than either homozygote.
- -lethal alleles in heterozygotes have selective advantage at equilibrium because disadvantages, like in lethal homozygotes, are balanced.
Fruit Fly/Ethanol Example
Empirical evidence that natural selection can cause change in allele frequencies.
When ethanol was added to their food, the allele that allowed for quick breakdown of ADH rapidly increased and gave the flies greater fitness.
Selection favoring heterozygotes
-Malaria/sickle cell (overdominance) (SS, Ss, ss)
- -V and L alleles in fruit flies
- (L is lethal, homozygous L individuals die)
Selection against homozygotes
- ex. Kuru/Fore population had prion (PrP) disease from cannibalism
- -resulted in wrong folding of cells and brain shrinkage/spongiform encephalopathy (?)
- -survivors had strong selection for heterozygote
ex. lethal alleles in flour beetles
Mutation as a source of new alleles
- -alone, mutation is a weak evolutionary force and it's changes are not evident in the population until much later.
- -normal mutation rate 1/10,000
- -important when combined w/ selection
Migration and example
def: movement of alleles b/n populations(gene flow/dispersal/colonization)
ex.Water snakes in Lake Erie (King)
Genetic Drift and Sampling Error
- -Random change in allele frequencies
- -Sampling error=chance difference b/n allele freq. in subset population vs. whole population
- ex. founder effect and bottleneck are chance events
Examples of Genetic Drift
- Clegg Study: Colonization of Silvereyes from Australia/Tasmania
- -steady decline in allelic diversity
- -furthest island had <.5 of mainland
ex2. identical immune alleles in cheetahs
- -example of founder effect/drift
- -isolated human population (3,000) with high frequency of achromatopsia allele due to chance
- -loss of function of cone cell protein=color blindness/poor vision/sensitivity