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Bio 201A


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Graph of two characters and their fitnesses
Adaptive landscape
(Incorrect) idea that offspring are literal phenotypic blends of parents (like an average)
Blending inheritance

Change in gene frequency due to mutation;

Equilbrium frequency;

Selection against mutation 

Deltap = -mu p - (1 - p) v

phat = v/(mu + v)

qhat =  rt(mu/s)

Additive fitness: each allele adds the same amount of fitness benefit per genotypic appearance
Codominant allele
Alternative equilibria
Positive frequency-dependent selection, heterozygous disadvantage
An alternative state of a particular gene at a locus
an ensemble of small populations, often exchanging gene flow; example
Metapopulation; less Swedish butterflies as you moved away
Average heterozygosity of a population
H = sum(# heterozygotes at each locus)/(100*n)
Birds and mammals have a cline such that larger animals occur in the north
Bergman's Rule
Broad-sense heritability


Proportion of phenotypic variation which is genetic 

Chance change sin allele frequencies
Genetic drift
Change in frequency in alleles for selection for a recessive allele
Delta q = spq^2/(1+sq^2)
Change in one generation due to selection
zbar = Beta * VA = R = h^2*s
Coefficient of relatedness
Probability of a gene shared by two individuals being identical by descent; r= sum ((1/2)^L)
Coefficient of Variation


Allows for comparison of deviaitons between different groups 

Conditions/equation for HArdy-Weinberg Equilibrium

1. Random Mating

2. Infinitely large population

3. No natural selection

4. No mutation

5. No migration

p^2 + pq + q^2 = 1, where

p = f(A), q = f(a), etc. 

Continent island model of migration

pI* = (1 - m) pI + m pC

Deltap = m(pC - pI)

Delta pI = -s pI qI^2/(1 - s + s qI^2) (for selection against p) 

Contribution of a genotype to the next generation
Convergent evolution
Pattern of having similar phenotypes evolve repeatedly in distantly related lineages; mammals and marsupials, pangalins and armadillos
Copy of a gene made on one chromosome due to improper crossing over
Correlation coefficient
rxy = sum(xbar -x) (ybar - y)/(N Sx Sy)
Detection selection
No equilibrium, phenotypic correlations (Bergman's rule), Survivors v. non-survivors (intemrediate galls win), functional studies (notothenoid enzymes), convergent evolution, molecular methods (DNA tests,statistics to look at positive selection)
Directional selection
Shifts mean; insecticide resistance
Disruptive selection
Mean same, variance increases; blacb-bellied seed crackers with extreme bills
Effective population size
  • Ne (as opposed to Nt)
  • Variation in fecundity (elephant seals - female hogging)
  • Uneven sex ratio (wasps and mites - female favored)
  • OVerlapping generations
  • Population size fluctuation (cheetah bottlene
Effects of genetic drift
  • evolution without selection
  • Loss of variation in a population
  • Increase in variation between populations
  • Probability of an allele becoming fixed = frequency of allele right now
  • Faster in smaller popula
elaborate ornaments are a handicap, so must have good genes to back it up
Handicap hypothesis
Equation for genetic variation
Equation for Phenotypic Variance
Everyone breeds equally and has equal fertility
Ideal Population
Everything on one side of the divide dies
Truncation selection
Evolution of female choice
  • Direct benefit (nuptial gifts, territory)
  • No direct benefit (leks)
Example of evolution
Selecting for drug-resitant bacteria
Examples of altruism
Ground squirrel warnings; pied kingfishers helping at the nest (PH>SH>Delay - sexy helpers)
External characteristics of an individual as afffected by genotype and environment
Females selecting for certain males get better offspring
Good genes hypothesis (peacock eyes)
Fluctuating selection

Temporal: Finch beaks and seed size changes with rain

Spatial: Flowers in a patchy field 

Frequency of an allele changes because of association with another, selected allele
Indirect selection
Gene flow example
Banded water snakes - still intermediates on the island despite selection for unbanded snakes
Gradual change in allele frequency or in the mean of character ove ra geographic transect; example
Cline; AP94 for salinity in Long Island Sound mussels; copper tolerance in grass near mines
Hamilton's Rule
An altruistic trait will evolve when B*r - C > 0
Heterozygous advantage
Overdominance; sickle cell allele
Heterozygous disadvantage
Underdominance; mutations more common in heterozygotes, balance favors more common allele
History of evolutionary theory

Plato: Ideal types

Aristotle: Scale of life

Ray: Natural complexity reflects God's thought

Linnaeus: As many species now as God first made

Agassiz: World not static

Buffon: Animals occaisionally altered into new specie

Inclusive fitness
Direct and indirect selection; fitness through whether or not blood relatives reproduce
Infinite number of character states
Continuous Traits
Inverse frequency-dependent selection
Rarer alleles favored; search image predation in fish
Kin selection
Promotes aid or assistance between individuals and descendent or non-descendant kin
Lamark v. Darwin

Lamark: Inheritance of acquired traits

Darwin: Evolution through natural selection 

Less parasites = better ornaments
Parasite hypothesis; mite of the swallow tail length
Maintenance of polymorphisms
<>Fluctuating selection, Inverse frequency-dependent seleciton, Heterozygous advantage (overdominance)
Males with higher trait values carry alleles for female preference
Arbitrary male hypothesis
Mating systems
Monogamy, polygamy
MHC alleles example
Najor Histocmpatibility Loci genotypic frequencis in Hasupai Native Americans not in equilibrium, either due to more miscarraiges for share dMHC alleles or non-random selection of unlike MHCs
Mutational speed experiment
E. Coli
Narrow-sense heritability

h^2 = VA/VP

 Proportion of phenotypic variablity due to additive genetic inheritance (proportion which is heritable/responsive to evolution

Negates induced mutation idea
4 cultures, 4 incubators; tree distribution for mutations
Net Fitness
Survival Fitness * Average fecundity
New population founded by a small number of colonists; example
Founder effect; old order Amish
Operational sex ratio
Ratio of available males to available females; skewed towards males (more effort for females)
pair bonds
Monogamy (birds); shrimp
Physical location of a gene
  • Polygyny: Males mate with many females; scramble competition (male race - horseshoe crabs), female defense (bats), resource defense (impalas), lek (male display territory - Uganda kobs)
  • Polyandry (Jacanas - males take eggs)
Postiive frequency-dependent selection
most common allele favored; warning coloration
Response to selection
R = h^2 *S
Selection differential
S = (t* - tbar), where t* is the mean of the trait before selection
Selection gradient

Slope of the regression of relative fitness on the character = Beta

Selection vs. drift dominance
Ne s >>1 vs. Ne s <<1
Set of genes belonging to an individual
Stabilizing seleciton
Mean same, variance lower; birth weight
Standard deviation
Theory of evolution by natural selection

1. Traits need to show variation

2. Some variation must be heritable

3. Individuals must differ in fitness

4. There must be a correlation between phenotype and fitness 

Three modes of selection
Directional, Stabilizing, Disruptive
Traits that have a finite number of character types
Discrete Traits
Transition vs. Transversion
Purine to purine, purine to pyramidine
Types of mutation by effect
  • Apomorphic - none
  • Hypomorphic - reduced fxn
  • Hypemorphic - increased fxn (usually dominant)
  • Xenomorphic - different fxn
Unit on a chromosome that encodes for one protein
Units of selection
Individual, Genes (meiotic drive - house mouse t locus), organelles (fast dead red mitchondria mutant in fungus), cells (cancer), group selection (flour weevils, viruses and hosts, species (snails overrespresenting), kin selection
V = sum(xbar - x)^2/n

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