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Population Genetics and Evolution (Factors that cause the gene pool to…
Population Genetics and Evolution
pop genetics
amount of different alleles in a pop and the way in which they inc, dec, same
tot # of alleles in all gametes in a pop
gene pool
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sex reprod. does not change the gene pool of a pop alone
would remain constant forever with no other factors
10 billion haploid sex cells
Factors that cause the gene pool to change
mutation
all genomes subjected to
occur continually
old alleles decrease in frequency
new alleles increase in frequency
accidents
events in which an org cannot adapt
ex. collision of a large meteorite with Earth
many phenomena qualify
can be small or large events
artificial selection
purposely change the allele freq. of a gene pool
selective breeding of crops and animals
gene pool is made up of alleles that have been art. sel. for thousands of years
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often in conjunction with artificial mutation
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natural selection
2 conditions before it can occur
progeny must differ from each other in their types of alleles
pop must produce more offspring than can survive
most sign. factor causing gene pool changes
survival of the fittest
most adapted to env suvive
least adapted die
num of ind that can survive in a habitat
pathogens
competitors
predators
differential survival can occur
those that have different phenotypes
Factors that are not part of N.S.
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Purpose
intention
planning
voluntary decision making
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Speciation
Natural selection causing a new species to evolve.
Occur in 2 ways
divergent speciation
pop evolve into new species
cont. unchanged
evolve into third new species.
if not kept homogeneous throughout entire range
reproductively isolated
abiological reproductive barriers
any physical nonliving feature preventing pop from exchanging genes
allopatric
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"geographic speciation"
2 or more pop that cannot interbreed
biological reproductive barriers
Any biological phenomenon that prevents successful gene flow
sympatric
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2 groups become rep. iso. even though they grow together
prezygotic isolation mechanisms
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act before a zygote can be formed
postzygotic internal isolation barriers
hybrid sterility
2 pop interbreed or artif. cross-pollinate viable seed
hybrid inviability
zygote or embryo dies early in development
phyletic speciation
gradually becomes so changed
gene flow
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movement of alleles through space
Seed Dispersal
Pollen Transfer
Vegetative Propagation
Evolution
Divergent Evolution
numerous types of species possible
Adaptive radiation
species rapidly diverges into new over short time
few million years
can occur in mainland populations if environ. changes suddenly & eliminates the dominant species
all offspring greatly resemble the first
"founder individuals"
initial gene pool is extremely small
genetic drift
if one seed is the founder
the original gene pool consists of two sets of alleles
Convergent Evolution
evolve to he point that they resemble each other strongly
cacti
origin of life
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Chemosynthesis
model using only known chemical and physical processes
rejecting all traces of divine intervention
A. Oparin
J. B. S. Haldane
Conditions on Earth before life
Chemicals present
second atmosphere
replaced the first atm.
release of gases from rock matrix
reducing atm
due to lack of O2 and powerful reducing agents
first atmosphere
mostly lost into space
Energy Sources
sun
UV
gamma radiation
energetic quanta
Heat
electricity
volcanic lightning
Time Available
had no limits
because of lack of free molecular oxygen
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ocean= "dilute soup"