Migration and Drift Flashcards
What is genetic drift?
Changes in allele frequency due to random sampling variation or chance variation in survival
What are mutations that don’t change the amino acid called?
Synonymous mutations, they are neutral
Define polymorphic and monomorphic
Polymorphic - Having more than one allele in the population
Monomorphic - having only one allele in the population
What happens to variation in different population sizes?
Variation is lost in small populations and retained in most large populations
What is Ne? How big is it?
The “effective” population size that loses variation at the same rate as the actual population.
It is usually less than the actual population size
What are reasons Ne is lower than N?
Competition for mates, the more genes that do not contribute to mating, the lower the Ne
Skewed sex ratios
What is migration in evolution?
Refers to movement between populations
What does migration do to allele frequencies in populations?
Migration homogenizes frequencies - tends to bring all populations to the same allele frequency
How does migration relate to drift?
It acts in the opposite way. Drift drives frequencies apart while migration brings them together. They balance each other
What are the two equations for divergence in populations? What do they do?
Measure Fst = 1 - (Hw/Ht)
Predict Fst = 1/(4Ne m + 1)
What is the equation for the Migration-selection balance
p* = Pm (m/m+S)
Explain the melanic peppered moth example
One species was light (typica) and one was dark (carbonaria), when the coal revolution happened trees became black and the black species was selected for up to 95% in polluted areas
What were the experiments done by Kettlewell on the moths?
Visual test for camouflage at 10 yards
Birds eating moths in an aviary filled with different backgrounds
Mark-release-recapture
What were the critiques of Kettlewell’s experiments?
If the moths didn’t actually rest on the trees, K exposed them to higher predation situations
The photos were staged to illustrate the appearance of the moths and they don’t actually rest on the trunk
