1: The forces of evo Flashcards
Define adaptation
Characteristic that enhances survival/reproduction of organism (relative to alternative states)
Describe the Hardy-Wienburg equillibrium
Describes allele frequencies in a pop. that is not evolving
Predicts frequencies in one gen compared to the previous gen
P2 + 2pq + q2 = 1
What are the conditions of the Hardy-Wienburg equilibrium?
No genetic drift (infinite pop.)
No mutations
No migration/immigration
Mendelian inheritance (no meiotic drive, gene drive)
No selection
Random mating
Why is the Hardy-Wienburg equillibrium useful?
- Tells us what happens if no evolution is happening
- Gives us a null model to compare to
How does genetic drift effect variation?
Drift lowers genetic variation
What force counteracts genetic drift?
Gene flow (migration)
Define natural selection
Differential survival and/or reproduction in organisms with a characteristic(s) that increase fitness
Define fitness
Probability of survival x av no. of offspring for a class of individuals
Describe fitness in Hardy-Wienburg
The fittest: W = 1
Not so fit: W = 0.5
The most unfit: W = 0
If the diff between w and 1 = selection coefficient (s)
E.g if a genotype has a fitness (W) of 0.9, s = 0.1
How do we know natural selection exists?
Correlations between trait and environment
Responses to experimental change in environment
Correlations between trait and fitness component
Signatures in the genome
Describe Endler (1980) study on Guppies in Trinidad
- Correlations between trait and environment
Coloration differs between predation rate
Probs due to trade-off between attracting females but not getting eaten - Responses to experimental change in environment
In predation environs spot size are selected to match the gravel size = camo - Correlation between trait and fitness component
The size increases in the absence of predation = due to sexual selection
