Transcript Population Genetics

Population Genetics
Population: a group of organisms of the same
species living together in a given region and
interbreeding.
Allele: Different forms of a gene for a trait.
Gene pool: the total of alleles present in a
population
Sources of variation in a
population
Mutations.
Genetic recombination (sexual
reproduction)
Migration (Founder effect: new colony
founded by only a few individuals)
Genetic drift (changes in a population’s
genes that are happening randomly)
Speciation (formation of new species)
Hardy-Weinberg Law
The frequency of genes leading to a certain
characteristic in a population does not change
unless evolutionary forces act on the population.
No mutation
No natural selection
Random mating
Big population (no inbreeding)
No migration in or out of the population.
Evolution of species (speciation)
Divergent evolution: species become different over a long period of time.
Adaptative radiation (species spread out to new territories).
Convergent evolution: Different species undergoing similar adaptations and
evolving more alike
Coevolution: two species evolve together, as they depend on each other
Extinction: Species disappear.
Gradualism: slow, gradual and even evolution.
Punctuated Equilibrium: no changes, punctuated with bursts of sudden
evolution
Mechanisms of speciation
Allopatric speciation:
A geographical process splits or fragments a
population such that the groups evolve
separately and cannot interbreed.
Continental drift.
Sympatric speciation
Mostly in plants
Hybridization
Polyploidy
• Autopolyploidy
• Allopolyploidy
Isolating mechanisms
Prezygotic barriers
Ecological barriers
Behavioral barriers
Mechanical barriers
Gametic barriers
Postzygotic barriers
Hybrid inviability
Hybrid breakdown
Hybrid sterility
Adaptations: Camouflage
More camouflage
Adaptations: Warning coloration
Adaptations: Seasonal changes
Adaptations: Mimicry
Types of Natural Selection
Directional selection
Stabilizing selection
Disruptive selection
Hybrid animals