Population Genetics and Evolution
concepts
population genetics
rates of evolution #
speciation
evolution & life origin
factors that change
gene pool
4 factors
artificial selection
natural selection
accidents
mutation
some situations
natural selection
does not operate
multiple selection pressures
occurs two ways
phyletic speciation
requires
movement of alleles
3 ways
seed dispersal
vegetative propagation
pollen transfer
divergent speciation
reproductive isolation
causes
abiological reproductive barriers
biological reproductive barriers
special type
adaptive radiation
convergent evolution
earth conditions
before life
atmospheric chemicals
energy sources
time available
chemosynthetically produced chemicals
formation of polymers
aggregation and organization
early metabolism
oxygen
presence of life
evolution
gradual conversion of
one species to
one new species
several new species
occurs by
natural selection
slow process
may require
thousands of generations
millions of years
Earth's age #
billions of years
discovered
in
independently by
mid 1800s
Alfred Russel Wallace
Charles Darwin
"survival of fittest"
terms
population genetics
abundance of alleles
within a population
and manner
in which
a particular allele
increases
remains the same
decreases
gene pool
number of alleles
in all
gametes in population
ratio remains same
if only
sexual reproduction considered
demonstrated by
G. H. Hardy
G. Weinberg
occurs continually
allele frequencies
new alleles increase
existing alleles decrease
significance depends on
population size
events that organisms
cannot adapt to
examples
meteorite collision
eliminates
organisms and alleles
may change
allele frequencies
volcanic eruptions
infrequent
hail storms
droughts
floods
continental drift
avalance
grazing animals
highway construction
when humans
purposefully change
allele frequency
in gene pool
examples
selective breeding of
crop plants
domestic animals
select
favorable traits
examples
high protein content
ability to survive
resistance to disease
in seeds
in
less fertilizer
less water
most significant factor
for occurrence
2 necessary conditions
population must
produce more offspring
than can survive
in that habitat
progeny must
affected by
predators
pathogens
limited resources
competitors
differ from others
in
types of alleles
factors not involved
purpose
intention
planning
voluntary decision
examples
genetically identical population
if adaptation impossible
no competition
or universal survival
would occur
in plowed fields
cut road sides
recently
burned area
flooded area
often
more than one
factor
change with
environment
time
examples
simultaneously
insects
weather
fungi
efficiency of
metabolism
water absorption
pleiotropic effects
may occur
"side effects"
some advantageous
some disadvantageous
depends on habitat
depends on habitat
typically
gradual
slow
most populations are
already well adapted
to their habitat
are especially
slow in
rapid in
ferns
Hawaiian asters
now 3 genera
new species
every 500,000 years
if
disruptive mutation
can happen
quickly
constructive mutation
can happen
slowly
when natural selection
causes
new species
to evolve
labeled this if
no fertile offspring
when two organisms
are crossed
aka gene flow
pollen grains
carry haploid genome
travels
by
wind
long distances
animal-mediated pollination
examples
birds
insects
dispersal mechanisms
long distance
short distance
example
fruits fall
next to parent
carried by
wind
floods
stream flow
small mobile species
that reproduce
vegetatively
if gene flow
does not
keep species homogeneous
are
physical nonliving features
that prevent
gene exchange
between two populations
when two species
grow separately
if speciateion results
examples
mountains
deserts
oceans
UV light
dry air
are
any biological phenomena
that prevent
successful gene flow
examples
prezygotic isolation mechanisms
discrimination pollinators
affected by
differences in
a flower's
fragrance
shape
flowering timing
allopathic speciation
grow together
aka geographic speciation
sympatric isolation
evolutionary changes
in pollinators
color
occurs before
zygote can form
environmental diversity
postzygotic
internal isolation barriers
hybrid sterility
when
artificial cross-pollination
produce viable seeds
but seed grows
into sterile plant
occasional interbreeding
results in
hybrid inviability
early death in
zygote
embryo
species rapidly diverges
into new species
in only
few million years
occurs when
species enter
new habitat
with little/no
competition
environmental stress
examples
Hawaiian Islands
Galapagos Islands
first offspring
resemble
founder individuals
gene pool is
extremely limited
new alleles
build up rapidly
genetic drift
rapid chantes
in gene pool
due to
higher subjectivity
to accidents
can occur
on mainland
if sudden
environmental changes
delete dominant species
when
two distinct species
have similar phenotypes
favored by
natural selection
examples
euphorbias
cacti
evolved in
American deserts
evolved in
African deserts
convergence of phenotypes
hypothesis
chemosynthesis
models life origin
using two processes
chemical
physical
proposed by
two scientists
A. Oparin
J.B.S. Haldane
in Russia
in England
initially
hydrogen
second atmosphere
several gasses
examples
produced by
release from
Earth's rock matrix
heavy meteorite bombardment
methane
ammonia
hydrogen sulfide
water
early on called
reducing atmosphere
due to
lack of
molecular oxygen
presence of
powerful reducing agents
most intense
from sun
UV radiation
gamma radiation
heat
from
coalescence of
gas and dust
radioactive decay
electricity
lightning storms
lightning around
volcanoes
unlimited
due to
lack of
molecular oxygen
1.1 billion years
from
Earth solidifying
to
arising of life
experimental tests
performed in
1953
consisted of
boiling water
reducing atmosphere
at bottom
at top
resulted in
formation of
complex organic compounds
from
monomers in
the early ocean
into masses
with
metabolism
example
fatty, hydrophobic material
not alive
aggregates would be
complete heterotrophs
when nutrient scarcity
needed enzyme
to synthesize
scarce molecules
from abundant molecules
evolution of
glycolysis
evolution of
two things
chlorophyll a
photosynthesis
resulted in
2 consequences
world can rust
created conditions that
selected for
aerobic respiration
liberation of
oxygen
2.8 billion
years ago
resulted in
oxidizing atmosphere
gradual transitions from
completely inorganic compounds
to
living bacteria
chemistry is
more complex
than nonliving objects
no unique properties
from nonliving objects
Cross link description: The beginning of the chapter emphasizes that Earth is billions of years old. This is further underscored by the discussion about oxygen becoming liberated 2.8 billion years ago, which was after the inital formation of Earth.
Cross link description: Natural selection is the primary factor in altering the gene pool. The example of cacti and euphorbias which grow in completely different continents clearly demonstrates how traits best suited for an environment are considered more "fit" and survive for multiple generations until its gene frequency is higher than the former.
Cross link description: Evolution is generally a very slow process. However, in adaptive radiation when a species is introduced to a new habitat with little to no stress or competition, new alleles can build up relatively quickly. This results in more rapid divergence of species.
several types possible
