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Population Genetics and Evolution (Speciation (Phyletic Speciation (Seed…
Population Genetics and Evolution
Population Genetics
The manner in which the abundance of an allele increases, decreases, or remains the same with time
Gene pool
Total number of alleles in all sex cells of a population
Mutation
Mutations occur continually
Cause new alleles to increase
Cause decrease in existing alleles
Significance depends on population size
Accidents
For example a large meteorite striking Earth's surface
Decrease alleles in a given area
Organisms cannot adapt to accidents
Can have a large or small impact on allele frequency
Natural Selection
Most fit survive
Most significant in changing gene pool
Progeny must differ in allele type
Population must produce more offspring than can survive or grow
Artificial selection
Process in which humans change the allele frequency of a gene pool
Selective breeding
Carried out with artificial mutation
Produces ornamental plants
Causes more often flowering
Causes longer flowering period
Rates of Evolution
Evolution is how a population adapts over time to their habitat
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Descendants become more diverse
Changes in evolution can cause loss of structure or metabolism
Speciation
Phyletic Speciation
Seed dispersal
Wind
Animals
Floods
Vegetative propagation
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Contribute to gene flow
Pollen transfer
Egg is fertilized and forms seed with new allele
Gene flow
New alleles arise and are selected for
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Allopatric Speciation
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Species divided, geographically, into two or more populations
Divergent Speciation
Reproductively isolated
Biological reproductive barriers
Biological prevention of gene flow
Prezygotic isolation mechanisms
Prevents pollen from moving from one plant to another
Abiological reproductive barriers
Non-living factor keep populations from gene exchange
Sympatric Speciation
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Two groups that become reproductively isolated even though they grow together
Convergent Evolution
Two species evolve resembling one another
Hybrid Sterility
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Two populations interbreed but offspring cannot reproduce
Evolution and the Origin of Life
Second Atmosphere
Caused by lack of molecular oxygen
Produced by release of gas from rock matrix
Reducing atmosphere
Energy Sources
Electricity
Radiation from the sun
Heat
Time available for origin of life
No limit on time available for chemosynthetic origin
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Aggregation and organization
Chemosynthesis
Rejects divine intervention
Models the origin of life using only chemical and physical processes
Formation of polymers
