15 Flashcards
How do populations separate? 3*
*Individuals from the population can move to a new portion
*Barrier that subdivides original population
*Large populations in a grand scale
Fixation index (Fst)?
Can help us measure the variance in allele frequency among subpopulations. Ranges from 0-1.
If subpopulations have identical allele frequencies, F_st = ?
0
If all subpopulations are fixed for different alleles, F_st = ?
1
Equation for F_st?
1/(4Nm + 1), N = population size, m = migration rate
Migration homogenizes or does not homogenizes allele frequencies?
Homogenizes
As migration increases, F_st increases/decreases?
Decreases
As population size increases, F_st increases/decreases?
Decreases
If F_st is higher/lower, there is more gene flow?
lower
Quantitative genetics?
Traits are not always coded for by two allele at one genetic locus. Many traits are quantitative traits and are the result of the expression of many genes.
What type of selection is greater interest for us?
Directional selection
Breeder’s equation?
Predicts the response to selection you should expect given the heritability of the trait you are interested in and the strength of the selection you impose.
R = h2 S, R = response to selection (differences of means of trait freq distribution before directional selection and after directional selection), h^2 = narrow sense heritability, S = selection differential (the difference between the mean trait values of animals in the population before selection and after selection)
How to calculate heritability?
Measuring the trait relatedness of the parent and offspring. We graph mid offspring value in response to mid parent value. The slope of the line is h2. h2 is a relative frequency
in real life, evolution really occurs when?
All the microevolutionary forces occur together, mutations, selection, drift, and gene flow
Current extinction rate
100 to 1000x faster than the normal extinction rate seen in history.
If population is small, then what does this mean about genetic drift?
More effects on genetic drift (arises because of random sampling of alleles)
Inbreeding depression?
When population gets small, genetic variation gets lost and recessive homozygous genotypes are more common. If these genotypes decrease organism fitness, smaller population sizes can become more dangerous.
Could natural selection save species undergoing inbreeding depression?
It depends. In very small populations, genetic drift is strong and can either reinforce or counteract the effects of selection. but if selection is acting at the same time, drift is always random.
In very large population, drift is minimal and selection is more powerful.
The relative importance of genetic drift vs selection depends on?
The population size (N) and selection coefficient (s)
If N*s < 1, selection or drift rules?
Drift rules
If N*s > 1, selection or drift rules?
Selection rules
Does genetic rescue work?
It can work
Can the fitness of alleles depend on the environment?
Yes
F_sd is always higher/lower for dens separated by roads?
Higher
