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Population Genetics and Evolution (Evolution (chemicals present in…
Population Genetics and Evolution
Population Genetics
the abundance of different alleles within a population
gene pool
total number of alleles in all sex cells of all individuals in a population
factors that cause gene pools to change
Mutation
decreases existing alleles frequency
new alleles increase
significance depends on population size
Accidents
events to which an organism can not adapt
artificial selection
process where human purposefully alter the allele frequency of a gene pool
selective breeding
of crops and domestic animals
used to produce ornamental plants and flowers for a longer time
natural selections
most significant factor causing gene pool changes
most adaptive survive
Two conditions met before natural selection can occur
population must produce more offspring than can possibly grow and survive
progeny must differ from each other in their type of alleles
differential survival can occur
factors not apart of natural selection
purpose
intention planning
voluntary decision making
Speciation
caused by natural selection allows new species to evolve
two fundamental ways of speciation
phyletic speciation
when one species gradually become so changed that is considered a new species
divergent speciation
when some populations of a species evolve into a new second species
while other populations either continued unchanged as original or evolve into 3rd species
Phyletic Speciation
gene flow
movement of alleles physically through space
occurs in many ways
pollen transfer
carry one full haploid genome
all alleles are present in pollen grains
seed dispersal
long distance dispersal method
if a seed is overlooked
alleles are transferred
as the seed germinates
grows as a new plant and reproduces
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vegetative propagation
asexual reproduction
which multicellular structures become detached from the parent plant
new individuals that are genetically identical to the parent plant
pollen transfer
Divergent Speciation
occurs when two separate species evolve differently from a common ancestor
when gene flow doesn't keep homogenous species throughout entire range
Barriers
biological reproductive barriers
any biological phenomenon that prevents successful gene flow
sympatric speciation
process through which new species evolve from a single ancestral species
in same geographic region
abiological reproductive barriers
any physical, non-living feature that prevents two populations from exchanging genes
allopatric/ geographic speciation
original species os physically divided into 2 or more populations
can't interbreed
adaptive radiation
special case of divergent evolution
in which a species rapidly diverges into many new species
founder individuals
all offspring greatly resemble
first gene pool is extremely small
convergent evolution
two distinct, unrelated species occupy the same or similar habitats, natural selection may favor same phenotype
Evolution
species present today have evolved from those that evolved in the past
chemosynthesis
most seriously considered hypothesis about the origin of life on earth
chemicals present in atmosphere
second atmosphere
hydrogen is such a light gas, most of this first atmosphere was lost in space
replaced by second atmosphere
reduction atmosphere
early second atmosphere
due to lack of molecular oxygen and presence of powerful reducing agents
energy sources
time available for the origin of life
had no limits
because of lack of free molecular oxygen
