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Ch. 17 Population Genetics and Evolution (Speciation (Divergent Speciation…
Ch. 17 Population Genetics and Evolution
Population Genetics
abundance of different alleles within a population
Factors that Cause the Gene Pool to Change
Mutation
existing alleles decrease in frequency
new alleles increase
Accidents
events in which organisms cannot adapt
alleles are destroyed
Natural Selection
most significant factor in gene changes
"survival of the fittest"
2 conditions must be met before natural selection can occur
population produce more offspring than can possibly grow and survive
progeny must differ from each other in their type of alleles
Artificial Selection
alleles manipulated by humans
used to produce ornamental plants
flower more abundantly
flower for a longer time
in conjunction with artificial mutation
Factors that are not apart of Natural Selection
purpose
intention planning
voulntary decision making
Speciation
when new species evolve from natural selection
Phyletic Speciation
one species is now considered a whole new species
takes millions of years
gene flow occurs in ways like
pollen transfer
pollen grains carry
one full haploid genome
all alleles of a plant
animal-mediated pollination
birds, insects, bees
though they can travel long distances
they only spread pollen through a smaller area
wind-distributed pollenination
can move to distant plants
seed dispersal
some seeds have long-distance dispersal mechanism
wind
floods
stream flow
vegetative propagation
producing small, mobile pieces that reproduce vegetatively
Divergent Speciation
population of a species evolve into a new second species
reproductive isolation
when alleles in one part of range does not reach alleles in another part
Abiological Reproductive Barriers
any feature that prevents 2 populations from exchanging genes
geographic speciation
allopactric
mountains are reproductive barriers
Biological Reproductive Barriers
any biological phenomenon that prevents successful gene flow
sympatric speciation
2 groups become reproductively isolated
prezygotic isolation mechanisms
act before a zygote can be formed
postzygotic internal isolation barriers
2 plants are 2 different
2 subpopulations can no longer interbreed
Adaptive Radiation
species rapidly diverges in a new one
in a extremely short time
founder individual
all offspring resemble their gene
genetic drift
gene pool changing rapidly and erratically
Evolution and the Origin of Life
chemosynthesis
models the origin of life
using only chemical and physical processes
Conditions on Earth Before the Origin of Life
Chemicals Present in the Atmosphere
reducing atmosphere
due to lack of molecular oxygen
and presence of powerful reducing agents
second atmosphere
produced by releases of gases
Energy Sources
Time Available for the Origin of Life
The Presence of Life