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Population Genetics & Evolution (17) (Speciation Speciation_events,…
Population Genetics & Evolution
(17)
Population Genetics
Abundance of dif alleles w/in population
Manner in which abundance
Increases
Decreases
Remains the same
Gene Pool
total number of alleles in all sex cells of all individuals of a population
Factors that cause change
Mutation
Accidents
Severe droughts for plants
Habitat destruction
Artificial Selection
Selective Breeding
Natural Selection
Most significant factor causing change
survival of the fittest
Individuals most adapted to environment survive
Individuals least adapted to environment die
Speciation
New species evolves from Natural Selection
Phyletic speciation
One species becomes so changed
Then considered new species
Divergent Speciation
Some populations evolve into new second species
Other population
Continue unchanged
evolve into new third species
ecology
Evolution & Origin of Life
Chemosynthesis
Most seriously considered hypothesis
Before life, Earth was different
Chemicals present could react spontaneously
Producing more complex chemicals
Continuous spontaneous reactions
No time limits
lack of free molecular oxygen
Phyletic Speciation
Gene Flow
movement of alleles physically through space
Pollen Transfer
seed dispersal
vegetative propagation
Divergent Speciation
Reproductive Isolation
alleles reach individuals in one part of range but not another
two fundamental causes
abiological reproductive barriers
Any physical, nonliving feature
Prevents two populations from exchanging genes
Biological reproductive factors
Any biological phenomenon
Prevents successful gene flow
Convergent Evolution
two phenotypically distinct
Species
organs
Metabolisms
strongly resemble each other
Responding to similar selection pressures
cacti and euphorbias
Earth before Life
Condensed from gases and dust
Hot and rocky
Mostly hydrogen
First atmosphere
Lost into space
Second atmosphere
Release of gases from
Rock Matrix
heavy bombardment by meteorites
Releasing atmospher
due to lack of molecular oxygen
Presence of powerful reducing agents
4.6 billion years ago
Species today evolved from those in the past
