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Chapter 17: Population Genetics and Evolution (Evolution and the Origin of…
Chapter 17: Population Genetics and Evolution
Population Genetics
gene pool
Factors that Cause the Gene Pool to Change
Accidents
events where an organism cannot adapt
natural phenomena
Artificial Selection
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process in which humans alter gene pool
selective breeding
desirable qualities
Natural Selection
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“survival of the fittest”
changes to gene pool
population sufficient to maturity
progeny differ in alleles
most important *evolution
offers genetic diversity
differential survival
Others
plants do not have intention or decision making skills
Mutation
occur continuously
depend mainly on population size
total alleles in sex cells of population
Situations in which Natural Selection does not Operate
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no operation in identical populations
must need competitors and reasons to adapt
Multiple Selection Pressures
allele benefits can depend on habitat
become more or less advantageous
abundance of different alleles and it’s increase or decrease
Speciation
Phylectic
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gene flow
Vegetation Propagation
small mobile pieces that reproduce vegetatively
Seed Dispersal
fall close to parent
can be carried by wind, water, animals
Pollen Transfer
one full haploid genome
dispersed rapidly by birds, winds, insects
movement of alleles physically thru space
gradually becomes so changed that it =new species
Divergent
Reproductive Isolation
Biological Reproductive Barriers
any biological phenomena that prevents gene flow
flower color, shape, fragrance etc.
speciation
sympatric
isolated but grow together
prezygotic isolation mechanisms
evolutionary changes due to differences in large populations
act before a zygote can be formed
Postzygotic internal isolation barriers
two sub populations considered separate
hybrid sterility
sterile plant
failure of synapsis
hybrid inviability
zygote dies early in development
Abiological Reproductive Barriers
any physical, nonliving feature that prevents two pops from exchanging genes
speciation
allopatric/geographic
species divided and can’t interbreed
mountains, rivers, desserts , oceans etc.
Adaptive Radiation
special case
diverge rapidly into many new species over short time
due to new habitat w/ less stress
can happen on mainland in sudden environmental changes
offspring resemble “founder”
new alleles build up fast
homogenous
genetic drift
change in gene pool erratically
heterogenous
original species, new species, side species,
Convergent Evolution
distinct species evolve to resemble each other
occupy similar habitat
Rates of Evolution
very slow
showcased by phenotypes
difficult to identify loss
Evolution and the Origin of Life
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Conditions on Earth before the Origin of Life
Chems. Present in Atmosphere
mostly hydrogen
second atmosphere
reducing atmosphere
Energy Sources
complex chem is second atmosphere
sun
heat
radioactive decay
radiation
volcanoes, electrical storms, intense lightning
intense energy
planetary cooling
accumulation of lakes oceans streams etc.
Chems. Produced Chemosynthetically
plausible model of chemosynthetic hypothesis
Formation of Polymers
monomers had to polymerize in the early ocean
Aggregation and Organization
into masses with organization and metabolism
fatty acids
heterotrophs
had some simple metabolism
no genetic storing
no natural selection
genetics introduced
efficiency=mutations
Early Metabolism
aggregates =heterotrophs
Oxygen
Oxidizing atmosphere
from early second atmosphere
evolution of chlorophyll a
rust
sedimentary rocks showcase age
critically important for all life
especially us humans
conditions for aerobic resp.
Presence of Life
long series of slow transitions
blurred line between living and nonliving
chemosynthesis
chemical and phys processes that allowed life
correlated with mutagens
natural selection causes new species to evolve
