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Population Genetics and Evolution (Evolution and the Origin of Life…
Population Genetics and Evolution
Speciation
Divergent speciation
Biological reproductive barriers
Prevents successful gene flow
Differences in flower, color, shape, or fragrance
Sympatric speciation
Grow together
2 groups become reproductively isolated
Example
Monkey flower
Mimulus lewisii
Adaptive radiation
Special case of divergent evolution
Species rapidly diverges into new species
Genetic drift
Founder individuals
Initial gene pool is extremely small
Can occur in mainland populations
Abiological reproductive barriers
Prevents 2 populations from exchanging genes
Physical, nonliving feature
Example
Mountain ranges
Geographic speciation
When speciation results
Allopatric
Convergent evolution
Result of natural selection favoring 2 phenotypes
Examples
Cacti
Euphorbias
Genotypes cannot converge
Phyletic speciation
Seed Dispersal
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Long-distance dispersal
Migratory animals disperse seeds
Caused by wind, flooding, & stream flow
Pollen transfer
Animal-mediated
Contributes to gene flow
Carry one haploid genome
Wind distributed
Ragweed
Grasses
Confiers
All alleles are present in pollen grains
Vegetation propagation
Various alleles come together by gene flow
Small mobile pieces
Reproduce vegetatively
Rates of Evolution
Populations are adapted to habitat
Would not survive if otherwise
New species develop very slowly
Complexity
Loss of structure
Change in metabolism can occur
Disruptive mutations
Outnumber constructive mutations
Occur rapidly
Very advantageous
Population Genetics
Situations in which natural selection does not operate
If all individuals are genetically identical
If survival is universal
Examples
Sides of a cut road
Recently burned area
Flooded area covered in rich sediments
Factors that cause the gene pool to change
Accidents
Can be small or large
Organisms cannot adapt to these
Examples
Molten rock destroying everything in an area
Volcanic eruption produces poisonous gas
Floods
Droughts
Artificial Selection
Humans change frequency of gene pool
Carried out in conjunction w/ artificial mutation
Examples
Selective breeding of crops
Selective breeding in animals
Mutation
Existing alleles decrease in frequency
New alleles increase in frequency
Natural Selection
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Can only act preexisting alleles
Does not cause mutations
Survival of the fittest
Conditions
More offspring than can be supported
Progeny must differ in their alleles
Most significant in gene pool changes
Factors that are not part of natural selection
Intention
Planning
Purpose
Voluntary decision making
Multiple selection pressures
Selection pressures can change
Most not caused by single factor
Features become more/less advantageous
Evolution and the Origin of Life
Conditions on earth before the origin of life
Energy sources
UV and radiation
Heat
Electricity
Volcanoes
Rainstorms
Time available for the origin of life
Chemosynthetic life
Had no time limits
Lack of free molecular oxygen
Chemicals present in the atmosphere
Second atmosphere
Replaced 1st atmosphere that was lost in space
Produced by released gases from rock matrix
Meteorites
Produced
Ammonia
Methane
Water
Hydrogen sulfide
Reducing atmosphere
Early second atmosphere
Lack of molecular oxygen
Powerful reducing agents
Chemicals produced chemosynthetically
Rock samples from moon
Contain amino acids
Contain organic compounds
Interior of meteorites
Contains
Sugars
Amino acids
Alcohols
Nitrogenous bases
Formation of polymers
Requires high concentration of monomers
Methods of concentration
Formation of seaside pools at high tide
Absorption by clay particles
Aggregation and organization
Step in chemical evolution
Aggregation of chemical components into masses with organization
Fatty, hydrophobic accumulated automatically
First aggregates
Formed at random
Controlled only by relative solubility
Not postulated
Early metabolism
Aggregates & first cells
May have absorbed ATP
Generated ATP by fermentation w/ glycolysis
Evolution
Electron transport systems
Hydrogen ion pumping systems
Glycolysis evolved early
Present in all organsims
Oxidative transport was nonexistent
Oxygen
Evolution of chlorophyll a & photosynthesis
Allowed for rust
Lowered concentration of free oxygen
Allowed for aerobic respiration
Oxidizing atmosphere
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Derived from early second atmosphere
Addition of oxygen from photosynthesis
The presence of life
Physics of living & nonliving things are identical
Important to understand complexity of process
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Complexity
Derived from this
Wind effects both
Natural Selection
