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Microevolution vs. Evolution
1
So... What mechanisms change a gene pool?
HOW might this happen with flowers?
Do you think bacteria are very "good" at copying
their own DNA?
In sexually reproducing organisms with
relatively long generations spans (humans),
most of the variation in not due to new mutations
but to scrambling of existing alleles.
1) Genetic Drift
2) Gene Flow
3) Mutation
4) Non random mating (sexual selection)
5) Natural selection
Microevolution and Evolution
Changes in allele frequency over time in a population
This is a phylogenetic tree
Some terms:
POPULATION
A local group of individuals belonging to
the same species.
POPULATION
GENE POOL
All of the alleles in all the individuals
that make up a population
GENE POOL
HARDY-WEINBERG EQUILIBRIUM
Populations that do no undergo change in allele frequency are therefore not presently evolving.
Several conditions must be in effect for this to be true of a population. We will return to these later...
HARDY-WEINBERG EQUILIBRIUM
Genetic Drift
A change in the gene pool of a population due to chance
Gene Flow
MUTATION
Natural Selection
The exchange of genes with another population
Natural selection and genetic drift
can influence whether a new mutation
increases in a population
Natural selection leads to ADAPTATION
BOTTLE NECK EFFECT
...Remember your SNPs!
Fertile individuals or their gametes migrate between populations
Disasters such as earthquakes floods, droughts, and fires may drastically reduce the size of a population.
By CHANCE, certain alleles may then be represented more frequently than others among the survivors.
Survival of the fittest!
Greater reproductive to success for individuals
with adaptive mutations!
FOUNDER EFFECT
For bacteria (which reproduce asexually)
mutations are especially important for genetic
variation.
What might "survival of the fittest" mean for a flower?
FOUNDER EFFECT
Hardy Weinberg Equilibrium
Five conditions are required in order for a population to remain at Hardy-Weinberg equilibrium:
1. A large breeding population
2. Random mating
3. No change in allelic frequency due to mutation
4. No immigration or emigration
5. No natural selection