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Ch. 17 Population Genetics and Evolution (Evolution and the Origin of Life…
Ch. 17 Population Genetics and Evolution
Concepts
mutations
#
more or less adapted to environment
new alleles in genes
deleterious
reproduces slowly
die without reproducing
evolution
survival of the fittest
extremelely slow
#
things go unnoticed
Charles Darwin and Alfred Russel Wallace
cannot discredit evolution or divine creation
Population Genetics
Factors that Cause the Gene Pool to Change
Mutation
one copy is very significant
even a single copy should not be ignored
all genomes subject to mutagenic factors
Accidents
events which an organism connot adapt
examples:
volcanic eruption
floods
hialstorms
droughts
meteorite hits Earth
Artificial Selection
humans purposefully change the allele frequency of gene pool
selective breeding for plants and animals
wheat, rice, corn
alter flower color and life length
acridine dyes, UV, gamma rays
Natural Selection
most significant factor of gene pool change
two conditions:
produce enough offspring
most seeds do not go far, making it hard to grow
progeny alleles must differ
if all were same, all could be susceptible
Factors the Are Not Part of Natural Selection
purpose
cannot say "Plants do something in order to..."
intention
planning
voluntary decision making
Situations in which Natural Selection Does Not Operate
examples:
freshly plowed field
sides of road cut
burned areas
flooded plain area
if survival is universal
Multiple Selection Pressures
there are many factors affecting mutations
examples:
pathogenic fungus
insect attack
drought
cold
need for pollination
one plant might be resistant to one but susceptible to another
Rates of Evolution
slow
most species present already adapt well
Hawaii aster seed
new species every 500,000 years
hard to tell
unless an identifiable effect on phenotype
Speciation
Phyletic Speciation
gene flow
movement of alleles physically through space
different ways:
pollen transfer
wind or animal/insect
can happen rapidly
seed dispersal
wind, steams, animal fur
new alleles spread throughout new site
vegetative propagation
species evolves into new species
Divergent Speciation
reproductively isolated
two fundamental causes
Abiological Reproductive Barriers
nonliving feature prevents populations exchanging genes
allopatric/geographic speciation
Biological Reproductive Barriers
biological phenomenon prevent gene flow
sympatric speciation
groups become reproductively isolated (even grown together)
prezygotic isolation mechanisms
act before zygote forms
hybrid sterility
two populations breed
produce sterile offspring
adaptive radiation
founder individuals
first initial gene pool
Convergent Evolution
unrelated species occupy similar habitats
two may grow to resemble another
cacti and euphorbias
Evolution and the Origin of Life
Conditions on Earth Before the Origin of Life
Chemicals Present in the Atmosphere
second atmosphere
reducing atmosphere
first atmosphere
hydrogen = too light
Energy Sources
UV and gamma rays from sun
heat
electricity
lightning
Time Available for the Origin of Life
lack of free molecular oxygen
had no limit
Chemicals Produced Chemosynthetically
Oparin and Haldane experiment
amino acids present
Formation of Polymers
high concentration of monomers
from clay?
Aggregation and Organization
aggregates
formed randomly
chemical components into masses
Early Metabolism
aggregates were heterotrophs
absorbing ATP
Oxygen
two conosequences
allowed the world to rust
created conditions selected for evolution of aerobic respiration
oxidizing atmosphere
from early second atmosphere
addition of oxygen
The Presence of Life
#
physics of living and nonliving are same
very complex
why so slow?
different views
more ways of gene change
