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Chapter 18: Population Genetics and Evolution - Coggle Diagram
Chapter 18: Population Genetics and Evolution
Population Genetics
gene pool
total # of alleles in all sex cells of all individuals of a population
factors that cause the gene pool to change
mutation
occurs continually
increase new alleles
pre-existing alleles decrease
accidents
events to which an organism cannot adapt
can delete new mutations
collision of large meterorite
volcanic eruption
floods
hailstorms
droughts
avalanche
construction
can be small or large
artificial selection
humans purposefully change allele frequency of gene pool
selective breeding
used to acquire beneficial qualities
corn
rice
wheat
use of mutagens
artificially select desired phenotypes
natural selection
survival of the fittest
most adapted to environment
survive
less adapted to environment
do not survive
two conditions required
population must produce more offspring than can possibly grow and mature
progeny must differ from each other in types of alleles
survivability of # of individuals in an environment
affected by
predators
pathogens
competitors
factors that are not part of natural selection
planning
purpose
intention
voluntary decision making
multiple selection pressures
loss of individuals and reduced reproduction
not caused by single factor
insect attack
drought
cold
need for pollinators
need for mechanism to disperse seeds
efficiency of metabolism
ability for membrane to pump ions
capacity to reduce nitrogen
situations in which natural selection does not operate
if individuals are identical genetically
if it is impossible to adapt to a certain situation
if survival is universal
Rates of Evolution
most populations are already well adapted to their habitat
few mutations produce a superior phenotype
difficult to identify presence of particular alleles
easy to identify if alleles have easily identifiable effect on phenotype
studies of evolution concern changes in gross structures
flowers
leaves
fruits
shoots
trichomes
Speciation
phyletic speciation
gene flow
as new alleles arise and selected for, spread through entire population
occurs in many ways
pollen transfer
grains carry one full haploid genome
all alleles of plant are present in pollen grain
wind-distributed pollen
ragweed
pollen can travel great distances
grasses
conifers
animal-mediated pollination
birds
insects
spread pollen through smaller areas
seed dispersal
seeds
fruits
can be carried by
wind
floods
stream flow
rafting (floating debris)
migratory animals
birds
vegetative propagation
small, mobile pieces that reproduce vegetatively
species remains relatively homogenous
definition: natural selection has caused a new species to evolve
divergent speciation
reproductive isolation
abiological reproductive barriers
any physical, nonliving feature that prevents two populations from exchanging genes
if speciation results
allopatric or geographic speciation
mountains
rivers
deserts
oceans
ultraviolet light
dry air
barriers to very long-distance wind dispersal of pollen
biological reproductive barriers
any biological phenomenon
discriminating pollinators
differences in flowering date
sympatric speciation
two groups become reproductively isolated even though they grow together
prezygotic isolation mechanisms
act even before a zygote can be formed
postzygotic internal isolation barriers
two subpopulations can no longer interbreed
hybrid sterility
1 more item...
hybrid inviability
1 more item...
evolutionary changes in pollinators
plants might have different
elevation
temperature
humidity
adaptive radiation
species rapidly diverges into many new species over an extremely short time
little or no competition or environmental stress exists
founder individual(s)
gene pool extremely small
all offspring greatly resemble the first
genetic drift
gene pool can change rapidly
convergent evolution
natural selection may favor the same phenotypes in two distinct, unrelated species that occupy the same or similar habitats
cacti
evolved in america from leafy trees
cactus spines are modified leaves
euphoribias
evolved in deserts of africa
euphorbia spines are modified shoots
only phenotypes converge, not the genotypes
Evolution and the Origin of Life
chemosynthesis
uses only known chemical and physical processes to model origin of life
conditions on earth before the origin of life
chemicals present in the atmosphere
earth
condensed from gases and dust 4.6 billion years ago
atmosphere composed of mainly hydrogen
1st atmosphere lost into space
replaced by second atmosphere
produced by release of gases from earths rock matrix composition due to heavy bombardment by meteorites
molecular oxygen absent
had already combined with other elements
water & silicates
reducing atmosphere
initially hot and rocky
energy sources
heat
coalescence of gas and dust to form earth
radioactive decay
uranium & radium
abundance of electricity
lightning triggered chemical reactions
volcanoes
produced electricity
time available for the origin of life
time unlimited due to lack of molecular oxygen
as much as 1.1 billion years between the time earth solidified and life arose
chemicals produced chemosynthetically
first experimental tests of chemosynthesis hypothesis
performed in 1953 by graduate student S. Miller, at U of Chicago
constructed container
boiling water at bottom
reducing atmosphere at top
electrodes discharged sparks into gases, simulating lightning
created atmospheric cycling of organic compounds
after a week of cycling
different substances including amino acids were present
formation of polymers
formation of seaside pools at high tide that evaporate after tide goes back out
intense sunlight heated pools
polymerization reactions could occur
return of high tide washed polymers into sea to accumulate
monomers accumulated in frozen pools
might of produced class of polymers different from those formed by evaporation at high temperature
clay
crystalline surface
may have contained concentrated monomers
aggregation and organization
fatty, hydrophobic material
accumulated automatically
oil slicks in quiet water
droplets in agitated water
fatty acids occupied outermost layer
accompanied by other molecules
proteins that had both hydrophobic and hydrophilic portion
interior
mostly hydrophobic
proteins with hydrophobic exterior and hydrophilic interior
higher complexity
oxygen
evolution of chlorophyll a and photosynthesis
two profound consequences
allowed world to rust
created conditions that selected for the evolution of aerobic respiration
todays atmosphere
derived from early 2nd atmosphere by addition of oxygen
oxidizing atmosphere
the presence of life
chemosynthetic theory
postulates long series of slow, gradual transitions from completely inorganic compounds to living bacteria
