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What is genetic drift?
A change in allele frequencies caused by random events/finite population sizes
What consequences does genetic drift have for genetic variation?
Randomly reduces variation, increased homozygosity
What effect does population size have on genetic drift?
Smaller size = faster and larger drift
What determines fixation probability?
Initial allele frequency
What is the founder effect?
change in allele frequencies as a result of the migration of a small subgroup of a population
How can serial founder effects explain human genetic variation?
Reduced variation the further away from the initial source of drift (Africa)
What effect does genetic drift have on deleterious mutations in small populations?
They increase in frequency because they act like neutral alleles
What is the consequence for the average fitness for a small population if deleterious mutations increase?
Fitness decreases
What is inbreeding?
reproduction among related individuals
What is inbreeding depression?
reduced fitness due to inbreeding
What are the three kinds of inbreeding?
Low population size, nonrandom mating (selfing), and random mating
How does inbreeding lead to reduced fitness?
Heterozygosity decreases and homozygosity increases
What are qualitative traits?
discrete traits that are controlled by 1 or 2 genes
What are quantitative traits?
continuous values, influenced by many genes and environment
What is heritability? How can it be measured?
the ability of a trait to be passed down from one generation to the next
It can be measured with Genetic Variation/ Phenotypic Variation
What is the importance of narrow-sense heritability?
Determines resemblance of parents and offspring and evolutionary change in response to natural selection
What is the breeder's equation? What is it used for?
R=h2 * S
Response to selection = heritability * selection differential
Used to predict change in trait
How can heritability estimates be interpreted?
Cross-fostering, twin studies, pedigree analysis
Will low or high values of heritability and selection differential lead to a small or large response to selection
high heritability/selection differential will lead to large response
What are the three modes of selection? What are their effects on mean and variance?
Directional: mean increases or decreases, variance smaller
Stabilizing: mean stays the same, variance smaller
Disruptive: mean stays the same, variance larger
What are three methods that adaptive significance can be studied?
Experiments
Observational studies
Comparative Method
What are four important components of an experiment?
Control groups
Randomization
Identical Conditions
Large Sample size
What is phenotypic plasticity?
the ability of an organism to change its phenotype in response to changes in the environment.
What are reaction norms?
lines or curves that depict phenotypic plasticity in a certain trait
What are genotype-by-environment interactions?
Genetic variation for phenotypic plasticity
What is sexual dimorphism?
phenotypic differences between males and females
What reasons does sexual dimorphism exist? (3)
Ecological reasons, roles in reproduction, sexual selection
What is sexual selection?
Natural selection for mating success.
What is asymmetrical parental investment?
When one sex invests more into offspring than the other
How can asymmetric parental investment explain what sex is more competitive or more choosy?
The sex that invests less is more competitive, the sex that invests more is more choosy
What are the various forms of intrasexual selection?
Combat, sperm competition, infanticide
What is combat?
Males fight for access to females
What are adaptations favored by combat?
Large body size, weaponry, armor, tactical cleverness
What is sperm competition, and under what circumstances does it occur?
When females mate multiple times, sperm from all males compete for fertilization
What are adaptations favored by sperm competition?
Large ejaculates, mate guarding, prolonging copulation, copulatory plugs, reduce remating probability
What are the different ways the choosy sex (usually females) benefits by being selective of prospective mating partners?
Choice for arbitrary traits
Exploitation of sensory biases
Direct benefits/resources
Good genes benefits
How can the presence of intersexual selection be explained?
Females might prefer certain traits
Females can get resources from a providing male
Some males have better genes
How would you test for good genes benefits as an explanation for an extravagant trait in males?
Determine paternity of offspring genetically
‐ Assess measures of offspring fitness and compare those between offspring of preferred and less preferred males
‐ Measure potential cofounding effects, e.g. do females provide more or less care for offspring of preferred males?
What are the four kinds of social interactions? How does each harm or benefit the actor and recipient?
Actor Recipient
Mutualism: benefit benefit
Selfishness: benefit harm
Altruism: harm benefit
Spite: harm harm
What is Hamilton's Rule?
Helping (altruism) is favored if the benefit (B) multiplied by the relatedness (r) is more than the cost (C)
What are the population genetic consequences of migration?
Homogenizes allele frequenciesIntroduces new variation from other populations
What is the coefficient of relatedness, and how does it influence the evolution of altruistic behavior?
Genetic similarity of two individuals
The more related they are, the more likely/ higher benefit an altruistic act is
What is inclusive fitness?
direct fitness + indirect fitness
If a behavior evolves because of the benefits such behavior confers on genetic relatives, it is said to have evolved through what form of selection?
Kin selection
