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Ch 17:Population Genetics & Evolution (Evolution and the Origin of…
Ch 17:Population Genetics & Evolution
Speciation
natural selection has caused a new species to evolve
can occur in 2 ways
phyletic speciation
one specie becomes so changed it is considered a new species
Pollen Transfer
alleles/genome can be distributed by wind
tranferable by animal
Seed Dispersal
seeds and fruit can be carried
wind
floods
stream flow
Vegetative Propagation
can contribute to gene flow
new pant grows from parent plant
divergent speciation
population evolves into new second species
Abiological Reproductive Barriers
feature that prevents two populations from exchanging genes
Biological Reproductive Barriers
prevents successful gene flow
Adaptive Radiation
species rapidly diverges into many new species
usually over short amount of time
Convergent Evolution
when 2 species evolve and strongly resemble each other
EX:
Cactus and Euphorbias
Rates of Evolution
Evolution can change rapidly
can result in loss of structure
loss of metabolism
some plants have grown without evolving into new species
Population Genetics
abundance of different alleles within a population
abundance of particular allele increases, decreases over time
gene pool
total number of alleles in all sex cells of individuals in population
Factors that cause gene pool to change
mutation
cause existing alleles decrease in frequency
causes new alleles to increase
accidents
events to which an organism cant adapt
causes alleles to be eliminated
artificial selection
when humans change allele frequency of gene pool
caused increased frequency of certain alleles &elimination of others
natural selection
survival of the fittest
causes genetic diversity
Evolution and the Origin of Life
Conditions on Earth Before the Origin of Life
Chemicals Present in Atmosphere
early earth
replaced with second atmosphere
composed of mostly hydrogen
Energy Sources
UV and Gamma radiation
heat was also energy
electricity was abundant
TIme Available for the Origin of Life
had no limits
lack of free molecular oxygen
Chemicals Produces Chemosynthetically
experiments led to observations of
mixture of amino acids and several substances present
today this experiment has been done with
other types of energy sources
including metal ions in water
Formation of Polymers
monomers present in early ocean had to polymerize
if life were to arise
Aggregation and Organization
chemical components into masses
Early Metabolism
aggregates were complete heterotrophs
absorbs all materials
modifies few molecules
Oxygen
allowed the world to rust
created conditions that selected evolution of aerobic respiration
Presence of Life
complex organisms
its easier to understand complexity
theory is difficult
physics of living and nonliving are identical
