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Chapter 17 Population Genetics and Evolution (Population Genetics (Natural…
Chapter 17 Population Genetics and Evolution
Population Genetics
Accidents
organism cannot adapt
examples: volcano, floods, droughts, etc.
selective forces
well adapted organisms survive accidents
Artificial Selection
humans change gene pool on purpose
produce seed for future crop
produce ornamental plants
used with artificial mutation
Factors that Cause the Gene Pool to Change
gene pool = total number of alleles in the sex cells of individuals
Mutation
occur continually
result in new alleles
results in existing allele frequency decreasing
abundance of different alleles in a population
Natural Selection
survival of the fittest
less adapted organisms die or are weakened
causes gene pool changes
genetic diversity ---> differential survival
differential survival based on phenotype
Factors that Are Not Part of Natural Selection
#
not included in natural selection
intention
planning
purpose
voluntary decision making
humans and primates work with intention
Humans are part of artificial selection
natural selection doesn't happen when environment can support everyone
many times single factors do not induce natural selection
Rates of Evolution
gene population change is usually slow
evolutionary change that results in loss happens quickly
evolution rate is complex
#
many generations go into gene change
Evolution and the Origin of Life
species today evolved from past species
#
chemosynthesis = reject all divine interaction
Conditions on Earth Before the Origin of Life
Energy Sources
highly reactive free radicals
heat available for energy
intense UV and gamma radiation
electricity was abundant
volcanos = hydrogen sulfide, ammonia, methane, water
Time Available for the Origin of Life
no oxygen
1.1 billion years between earth and life on Earth
no limits to time
Chemicals present in the Atmosphere
first atmosphere = lost to space
second atmosphere = reducing atmosphere
second atmosphere = produced by released gases
reducing atmosphere = ;ack of oxygen presence of reducing agents
Chemicals Produced Chemosynthetically
electrodes + gas = lightning
meteors and moon rocks show us what they pass through in the atmosphere
chemosynthetic hypothesis works for monomers
Formation of Polymers
monomers had to be very concentrated
seaside pools were concentrated monomers
monomers had to polymerize for life
clays...catalysts?
Aggregation and Organization
first aggregates formed at random
aggregates evolved to "use" products
masses of chemical components
Early Metabolism
aggregates used scarce molecules was advantageous
oxidative electron transport not possible because no oxygen
first aggregates were heterotrophs
Oxygen
oxidizing atmosphere = add oxygen from photosynthesis
oxygen = ozone = prevent UV radiation
chlorophyll a and photosynthesis evolution released oxygen
Speciation
two different species cannot have fertile offspring
phyletic speciation vs divergent speciation
a new species occurs
Phyletic Speciation
Pollen transfer
animal mediated pollination
one full haploid gamete
Seed Dispersal
seeds carried by wind, water, etc.
new alleles produced
long or short distance
gene flow = physical movement of alleles in space
Vegetative Propagation
alleles at different geographic sites come together through gene flow
small mobile pieces contribute to gene flow
Divergent Speciation
reproductively isolated = species from one area do not reach the other ares
Abiological Reproductive Barriers
#
physical barrier
allopatric/geographic speciation = speciation occurs
deserts and oceans are barriers
Biological Reproductive Barriers
sympatric speciation = isolation even when grown together
biological barrier that prevents gene flow
evolutionary change in pollinaters
prezygotic isolation mechanisms = no pollination or fertilization occurs
postzygotic internal isolation barriers = no interbreeding is successful
hybrid sterility = postzygotic barrier
hybrid inviability = fertilization results in early death of zygote
Adaptive Radiation
one species ---> many new species
divergent evolution
founder individual = initial gene pool
genetic drift rapid gene pool change
convergent evolution = two species evolve to strongly resemble each other
