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Population Genetics and Evolution (Evolution and the origin of life…
Population Genetics and Evolution
Specification
two pathways
divergent speciation
some population of species evolve into new second species
while other populations continue unchanged as the original
abiologcal reproductive barriers
physical, nonliving feature that prevents two populations from exchanging genes
allopatric
two or more populations
cannot interbreed
biological reproductive barriers
biological phenomenon that prevents successful gene flow
effective barriers
differences in flowers
shape
fragrance
color
sympatric speciation
two groups become reproductively isolated even though they grow together
prezygotic isolation mechanisms
act before a zygote can be formed
prevent pollen moving from one plant to another
hybrid sterility
earliest postzygotic barriers
two populations interbreed
produce viable seed
grows into sterile plant
adaptive radiation
special case of divegent evolution
species rapidly diveges into many new species
founder individuals
initial gene pool is small
all offspring greatly resemble the first
one seed is the founder
genetic drift
change rapidly and erratically
phyletic speciation
one species gradually becomes so changed
becomes new species
pollen transfer
carry one full haploid genome
can travel long distances
ragweed
grasses
conifers
seed dispersal
fruits and seeds of some plants
falls close to parent
can be carried by wind or floods
can be carried to islands
by being trapped on debris
vegetative propagation
contribute to gene flow
species produce small, mobile pieces that reproduce vegetatively
gene flow
movement of alleles thorugh space
convergent evolution
two species may evolve
resemble each other strongly
two unrelated species occupy the same area
natrual selection
favors same phenotypes in each
natural selection causing new species to evolve
Evolution and the origin of life
conditions on earth before the origin of life
second atmosphere
rock matrix
composing earth
heavy bombardment by meteorites
reducing atmosphere
lack of molecular oxygen
presence of powerful reducing agents
composed from gases and dust
formation of polymers
present in early ocean
had to polymerize for life
requires high levels of monomers
oxygen
oxidizing atmosphere
addition of oxygen from photosynthesis
allowed world to rust
created different weather conditions
the presence of life
chemosynthetic theory
postulates long series of flow
transitions from completely inorganic compounds to living bacteria
Population Genetics
abundance of different alleles within population
gene pool
total number of alleles in sex cells in population
factors that cause the gene pool to change
mutation
existion alleles decrease in frequency
new alleles increase
accidents
organism cannot adapt
example:
collision of meteorite with earth
such things happen as volcanic ash
floods
wildfires
artificial selection
the change of alleles in gene pool
by humans
natural selection
most significant factor causing gene pool changes
survival of the fitest
factors that are not part of natural selection
purpose
planning
intention
voluntary decision making
situations in which natural selection does not operate
not work if individuals of population are identical genetically
multiple selection pressure
pathogenic fungus
plants are affected by
insect attack
drought
cold
need for pollinators
need for mechanism to disperse seeds
