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population genetics and evolution (evolution and origin of life (early…
population genetics and evolution
population genetics
situation where natural selection don't operate
it doesn't operate if individual of population are genetically identical
or there is no competition on its habitat for growth
it doesn't operate in plowed field.
Multiple selection pressure
certain aspects are more important that others, cold weather are frequent then it need to have adaptation abilities for it than summer.
as the time changes selection pressure changes
plant have pressure to adapt on all aspects of their environment
factors causing gene pool to change
accidents
events to which organisms cannot adapt
allele frequency of the gene pool is altered due to accidents
also describes for the stronger plants that survives the accidents whereas smaller dies.
artificial selection
change of alleles frequency of a gene purposefully
example:selective breeding of crops like wheat, rice corn
looking for plant that is resistant to disease, ability to survive with less water and fertilizer.
often carried out with conjuction and artificial mutation
mutation
due to mutation, existing alleles decrease in frequency and new alleles increase.
mutation depends on population size.
mutation describes the adaptation and is random, constant process.
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changing the structure of gene
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natural selection
most significant factor causing gene pool change
described as survival of fittest
1st condition to met before natural selection can occur
population must produce more offspring than it can grow and survive maturity.
ground can have many seedlings but all of them cannot grow on that habitat due to less room to accomodate.
also the survival is affected by pathogens, predators and competitors
2nd condition to met before natural selection
if they are identical, all are affected same way all grow poorly and none reaches maturity.
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all grows identical which means no natural selection occured
progeny must differ from each other in their types of alleles
it describes which mutation will survive and which die on
factors that are not part of natural selections
purpose, intention, planning and voluntary decision making are not part of natural selection.
example: plant don't produce nectar to attract pollinators. those plants that produce nectar in past happen to be pollinated more often than others. so, alleles for nectar production was increased. but plants this is not plant intent or planning.
rates of evolution
rate of change of genotype over a time.
related to severity of evolutionary pressure put on the species.
if there is no changes is habitat for long time the evolution rate is slow and small base rate of genetic mutation.
if plants are in rapidly changing environment evolution rate is
greater
speciation
divergent speciation
biological reproductive barriers
biological phenomenon that prevents successful gene flow
it results in numerous types of new species
one subpopulation changes to a new species while other remains unchanged as original species.
adaptive radiation
it occurs when the species enters a new habitat where little or no competition, environmental stress exists.
special case of divergent evolution in which species rapidly diverges into many new species over an extremely short time
abiological reproductive barriers
physical or non living feature that prevents two population from exchanging genes.
divided to
allopatric
geographic speciation
convergent speciation
if two distinct and unrelated occupy same habitat, may favor the phenotype in each and resemble each other strongly.
phyletic speciation
seed dispersal
seed of some plants falls close to parent
some seed species have long distance dispersal mechanism.
as they have long distance disperse they grow in different habitat and new allele can be spread throughout new site
vegetative propagation
if species produce small, mobile pieces that reproduce vegetatively, they help in gene flow.
alleles arise at different geographic site come together by gene flow.
pollen transfer
allele movement is rapid.
pollen grain has one full haploid genome with all its alleles and if pollen grain sperm fertilize with egg new seed is formed with new allele.
evolution and origin of life
formation of polymers
polymer reaction occurs when intense sunlight is present and the place is hot.
monomers accumulates when pond and seaside froze which makes monomers highly concentrated.
aggregation and organization
aggregation of chemical component into masses that has same organization and metabolism.
chemicals produced chemosynthetically
alcohols, sugars amino acids and nitrogen bases occur in nucleic bases.
represents the plausible model.
early metabolism
aggregates are complete heterotrophs absorbing materials from sea and ocean.
as it continues to consume nutrients scarcity occurs.
one gets the advantage over others grown and reproduce rapidly.
condition of earth before origin of life
energy sources
early secondary atmosphere was exposed to powerful source of energy
foremost was uv radiation gamma from sun.
heat was the another source of energy to power reaction.
coalescence of gas and dust from earth.
radioactive decay of heavy elements like uranium and radium
time available for the origin of life
origin of life had no limits because of lack of free molecules.
without oxygen, no agent present to breakdown and decompose of chemicals
chemicals present in the earth
first, atmoshphere was made of hydrogen which was lost into space
second atmosphere produced by release of gases from rock matrix.
oxygen
created conditions that selected for evolution of aerobic respiration.
it allowed world to rust
the presence of life
a long series of slow gradual transition from completely inorganic to living bacteria
its more important to understand process of complexity
