Population Genetics and Natural Selection Flashcards
Evolution
- Gradual change at the population level
- Change in frequencies of alleles/phenotypes in a population
Peppered moth
Biston betularia
Two major mechanisms of Evolution
Genetic Drift
Natural Selection
Natural Selection vs Genetic Drift
Natural Selection
- traits chosen based on survival advantage
- Not random
- Requires evidence
Genetic Drift
- random selection
- traits are loss or fixated through completely random chance events
- default mechanism of evolution
Natural Selection
Selection of traits based on fitness [the ability to survive and pass down traits/genes to offspring]
Red Queen Hypothesis
The same traits will not always be ideal due to everchanging environmental conditions; evolutionary arms race
Adaptation
Trait that increases fitness
Ecospecies/Ecotype
geographically distinct VARIATION of a species responding to specific environmental conditions; they can still reproduce with one another
4 hallmarks of Natural Selection accdg to Charles Darwin
- Organisms beget organisms
- Some variations are heritable
- More offspring than can be supported by the environment are produced each generation
- Some individuals have higher fitness than others
Punctuated Equilibrium
major change causes branching into new species
Speciation requires ____ ____
reproductive isolation
3 Types of Natural Selection
Stabilizing selection
Directional selection
Disruptive selection
Genetic Variation in Alpine Fish
Movement of cold adapted aquatic species into the headwaters of glacial valleys around the Alps created clusters of geographically isolated populations; Douglas and Brunner used microsattelite DNA to conclude Coregonus populations are highly diverse with high levels of differentiation
Hardy Weinberg assumptions
- Random mating
- No mutations
- Large population size
- No immigration
- Equal survival and reproductive rates of all genotypes
Heritability
evolution through natural selection
h^2 = Vg/Vp = Vg/(Vg+Ve)
Evidence of genetic drift in chihuahua spruce
Picea chihuahuana now restricted to peaks of Sierra Madre Occidental in New Mexico;
Ledig et al. examined if species lost genetic diversity as a consequence of reduced population size
Significant positive correlation between population size and genetic diversity
For large organisms,
if population <500, __________
if population <50, _________
genetic drift is more likely to happen
inbreeding is more likely to occur
Genetic Diversity and Butterfly extinctions
Frankham and Ralls point out INBREEDING contribute to higher extinction rates in small populations
reduced fecundity, depressed juvenile survival, shortened life span
Saccheri et al. studied Glanville fritillary butterflies and found that populations with high inbreeding had high probability of extinction
Artificial selection
Selective breeding to produce or maintain desireable traits
Genetic engineering
introduction or deletion of genes in organisms; produces GMOs