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Population Genetics and Evolution (Evolution and the Origin of Life…
Population Genetics and Evolution
Population Genetics
Factors that Cause the Gene Pool to Change
mutatuions
usually have little effect but should not be ignored
accidents
avalanche, hail storm. things that alter or destroy plants
artificial selection
humans purposefully change gene pool; like crop plants or animal breeders
natural seleciton
most significant in causing changes. (does not cause mutations)
pop. must produce surplus and live to be mature
progeny must differ from each other in their alleles
affected by pathogens, predators etc
Situations in which Natural Selection Does Not Operate
if all population is same genetically or if it is impossible for plant to adapt to env.
happens in newly opened habitats
Multiple Selection Pressures
weather
insects
need for pollinators
Rates of Evolution
changes do not happen rapidly
mutations usually don't cause phenotypic change in an overall population
aster eater seed in Hawaii is an ex. of ones that do
changes that result in loss of a structure of metabolism happen fast
Speciation
Phyletic Speciation
pollen transfer
wind and animal help spread pollen
seed dispersal
things carry seeds far and allele is transferred
vegetative propagation
travel around part..homozygous but transform
Divergent Speciation
abiological reproductive barriers
physical non-living feature prevents 2 pop. from exchanging genes
allopatric speciation
biological reproductive barriers
biological phenomenon prevents successful gene flow
sympatric speciation
adaptive radiation
species diverge into new species very fast
Ex. animal enters new habitat and has small competition
Convergent Evolution
different but same phenotype so they look alike
Evolution and the Origin of Life
Conditions on Earth Before the Origin of Life
chemicals present in the atmosphere
mostly hydrogen.
second atmosphere included H2S, NH3, Ch4 and H2O
energy sources
Ex- uv, heat
time available for origin of life
no oxygen=no breakdown= life had no limits
Chemicals Produced Chemosynthetically
miller experiment concluded essential for life mol. can be formed with it (pg. 480)
Formation of Polymers
monomers accumulate= polymerization
Aggregation and Organization
fatty hydrophobic accumulated automatically
fatty acids =outer most later
certain proteins= large regions of hydrophilic sites
Early Metabolism
aggregates consume nutrients= scarcity
natural selection probably occurred which lead to more and more metabolic pathways
Oxygen
for a long time photosynthesis used pig. bacteriochlorophyll ..sulfur from hydrogen
chlorophyll a evolved. o2 was released
other Important effects= under uv light oxygen=ozone
