Ch 1 - Evolution Flashcards
Evolution definition
change in gene pool gene frequency
What process drives evolution?
Natural selection
What is natural selection?
population better adapted to gain resources than others
What is R in a population size over time graph?
rate of growth
What is K in a population size over time graph?
carrying capacity
What happens if population size exceeds the carrying capacity?
the population could crash
What is the ideal R in a population size over time graph?
sigmoid curve
-grow until just before carrying capacity is reached, then plateau
What is the HWP?
Given certain conditions, there’d by a genetic equilibrium that could be maintained indefinitely
What is genetic equilibrium?
allelic freq will not change over time
What are the conditions required for HWP?
- Random mating
- Population must be large enough
- No migration
- No mutations
- No natural selection
Why is random mating not feasible?
mating is almost always non-random
-can be assortative or non-assortative
What is assortative mating?
individuals choosing mates based on phenotype
What is genetic drift?
change in allelic frequency due purely to chance
What are the two special cases of genetic drift?
bottleneck effect
founders effect
What is the founders effect?
when a smaller populations becomes isolated from a larger population
-The smaller population could be drastically different from the original population
What is the bottleneck effect?
when a population shrinks to a much smaller number, then grows
-after shrinking, the survivors may not express all the alleles from before shrinking
Why are no mutations not feasible
mutations never stops
Why is no natural selection not feasible?
natural selection always occurs
Natural selection occurs as long as:
there is variation in population
-genetically based
What are qualntitative traits of natural selection?
show incremental variation
-height on a bell curve
What are the different types of quantitative selections?
stabilization selection
directional selection
disruptive selection
what is stabilization selection?
(a quantitative )
- phenotypic average is formed
- phenotypic extremes selected against
What is directional selection?
(a quantitative selection)
-one phenotype extreme is favored over the other extreme
What is disruptive selection?
both phenotypic extremes are favored over the average
What are the different types of qualitative selections?
show disjunct variations
- manelian traits
- frequency dependent selection
What increases variation in populations?
mutations
gene flow
sexual recombination
What decreases variation in population?
selection
genetic drift
