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Genetics (Population Genetics ((Factors that cause the gene pool to…
Genetics
Population Genetics
Factors that cause the gene pool to change
Accidents
events that an organism cannot adapt
artificial selection
human intervention
purposely change alleles in gene pool
selective breeding
Mutation
occur continually
existing alleles decrease in frequency
new alleles increase
natural selection
Survival of the fittest
Most adaptable survive
population must produce more offspring than can survive to maturity
progeny must differ from each other ( Types of Alleles )
Gene Pool
Multiple Selection Pressures
loss of individuals/reduced reproduction
not caused by single factor
drought
temperature change
pathogens
pollinators
insects
mechanism to disperse seeds
Where natural selection does not operate
Speciation
Convergent Evolution
occupy the same/similar habits
may favor same phenotypes in each species
Two groups cannot converge to same species
cacti
evolved from leafy trees in the Americas
euphorbias
evolved in Africa
Two distinct unrelated species
Divergent Speciation
abiological reproductive barriers
Physical/nonliving feature
allopatric/geographic speciation=speciation results
biological reproductive barriers
Any biological phenomenon
discriminating pollinators
evolutionary changes in pollinators
differences in flowering times
sympatric speciation
two groups reproductively isolated
postzygotic internal isolation barrier
subpopulations can no longer interbreed
2 more items...
act before zygote can be formed
Population diverges
others in population can be unchanged
Into a new, second species
or become a new, third species
Rates of Evolution
Most Populations already well adapted
Evolution Studies concern gross structures
Flowers
Leaves
Fruits
Shoots
Trichomes
easily identifiable if phenotype is affected
Very few mutations produce a superior phenotype
evolution and the origin of life
chemosynthesis
chemosynthetic theory = hypothesis of the origin of life
chemosynthesis model
using only known chemical physical processes
rejects divine intervention
proposed by a oparin in 1924
Conditions on Earth Before the Origin of Life
approximately 4.6 billion years ago