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Ch 17 Population Genetics and Evolution (Evolution and the Origin of Life,…
Ch 17 Population Genetics and Evolution
Population Genetics
Factors that Cause the Gene Pool to Change
Mutation
occurs constantly
existing decrease while new increase
Accidents
an organism cannot adapt
ex. large meteorite hits earth
artificial selection
process in which humans purposefully change the allele frequency of a gene pool
crop plants and domestic animals
artificial mutation
natural selection
the most significant factor causing the gene pool changes is usually described as survival of the fittest
2 ways for it to occur
population must produce more offspring that can possibly grow and survive to maturity in that habitat
progeny must differ from each other in their types of alleles
Situations in which Natural Selection Does Not Operate
cannot happen if all individuals are identical
competition does not occur
sides of a road are cut
Multiple Selection Pressures
insect attack
drought
cold
need for pollinators
deals with the abundance of different alleles within a population and the manner in which the abundance of a particular allele increases, decrease, or stays the same
Rates of Evolution
most populations are relatively well adapted to their habitat
very few mutations cause new phenotypes
difficult to identify the presence of particular alleles in a population
Speciation
Phyletic Speciation
gene flow
the movement of alleles physically through a space
pollen transfer
seed dispersal
vegetative propagation
Divergent Speciation
abiological reproductive barriers
any physical, nonliving feature that prevents two population from exchanging genes
allopatric
if speciation occurs
biological reproductive barriers
any biological phenomenon that prevents successful gene flow
sympatric speciation
when two groups become reproductively isolated even though they grow together
prezygotic isolation mechanisms
phenomena that prevent successful interbreeding of two populations but act so early that fertilization is not possible
postzygotic internal isolation barriers
same as prezygotic but occurs AFTER
hybrid sterility
two populations occasionally interbreed or are artificially cross-pollinated and produce viable seed
adaptive radiation
species rapidly diverges into many new species over a short time
genetic drift
in a small gene pool, the alteration in allele frequencies mostly by accidents rather than natural selection
Convergent Evolution
convergent evolution
evolution of two phenotypically distinct species, organs, that they strongly resemble each other
ex=cacti and euphorbias
Evolution and the Origin of Life
Conditions on Earth Before the Origin of Life
second atmosphere
produced by release of gases from the rock matrix composing Earth
reducing atmosphere
energy sources
Chemicals Produced Chemosynthetically
various organic compounds from the moon
meteorites
Formation of Polymers
Aggregation and Organization
formed at random
inheritable
are not postulated to have been alive
Early Metabolism
glycolysis
energy metabolism
Oxygen
allowed earth to rust
created conditions that selected for the evolution of aerobic respiration
The Presence of Life
