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Population Genetics and Evolution (Hardy Weinberg Equation (Equation…
Population Genetics and Evolution
Evolution
Gradual conversion of one species into one or, in some cases,several new species
occurs by Natural selection
Slow process
Gene Pool
total number of alleles in all the sex cells of all individuals of a population
Factors that cause the Gene Pool to change:
Mutation
Accidents
Artificial Selection
artificial change in the allele frequency of a gene pool
Example: selective breeding of crop plants and domestic animals
Natural Selection
survival of the fittest
most significant factor causing gene pool change
Two conditions: 1. offspring able to grow in the habitat,
progeny must differ from one another
Natural Selection
Speciation
change in the phenotypic population
natural selection
Phyletic speciation
one species changing to new species
gene flow
pollen transfer,
seed dispersal
Vegetaive propagation
Divergent Speciation
either change to new species or remain original or change to a third species
reproductively isolated
Abiological Reproductive barrier. eg: mountain ranges species
Biological Reproductive Barrier. Eg: monkey flower
Adaptive Radiation: colonies of Hawaii
Genetic drift: rapid change in gene pool
Convergent evolution
unrelated species evolving to resemble
Example: convergence of cacti and euphorbias
Hardy Weinberg Equation
predicts an equilibrium-unchanging allele and genotype frequencies
No new mutation
No Genetic drift
No migration
no selection
random mating
Equation
p2+2pq+q2=1
p2= genotypic frequency of RR
2pq= genotypic frequency of Rr
q2= genotypic frequency of rr
Conditions on earth before Evolution:
Chemical present in the atmosphere
exposed to powerful sources of energy
Time availability for the origin of life
Elapse of 1.1billion years
Chemicals produced Chemosynthetically
Polymers Formation
Aggregation and Organization
Early metabolism
The presence of Life
Oxygen
Polymorphism:
observation that many traits display variation within a population
Example: individuals from the same species, differ in alleles that affect color and pattern
Genetic Equilibrium
condition of an allele or genotype in a gene pool (such as a population) where the frequency does not change from generation to generation.
Directional Equilibrium
mode of natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype
Stabalizing Selection
population mean stabilizes on a particular non-extreme trait value.
Disruptive Selective
changes in population genetics in which extreme values for a trait are favored over intermediate values.
