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Population Genetics And Evolution (Evolution and Origin of Life (Condition…
Population Genetics And Evolution
Population
Genetics
factors that cause the gene pool to change
mutation
existing alleles decrease in frequency & new alleles increases
accidents
damaged due to several natural disasters
artificial selection
process in which human purposefully change the allele frequency of gene pool
natural selection
survival of fittest
factors not part of natural selection
purpose, intention, planning or voluntary decision making
situation in which natural selection does not operate
deals with the abundance of different alleles
manners in which abundance of a particular allele
the manners in which abundance of a particular allele
within the population
multiple selection pressure
Rates of Evolution
most population are relatively well adapted to their habitat, or they would not exist
at the extremes, many seedless plants like lycopods, fern have perished for 10 millions of years without diverting into new species
very rapid speciation has occur in a group of asters in Hawaii
any new mutation results in a more adaptive structure only if the effects of new allele fits in
evolutionary changes result in the loss of structure due to the disadvantageous character/structure
Evolution and Origin of Life
Condition of Earth before the origin of life
Chemical presents in the atmosphere
condensed gases and dusts about 4.6 billion years ago
first atmosphere was replaced by second atmosphere
early second atmosphere was reducing atmospheres
due to lack of molecular oxygen & presence of powerful reducing agent
Energy Sources
one heat source was the coalescence of gas & dust from the Earth
volcanoes
Time available for the origin of life
time available for the chemosynthetic origin of life had no limits
the ocean of that time was called dilute soup or primordial soup
lack of free molecular oxygen
containing water, salts and numerous organic compounds
Chemicals Produced Chemosynthetically
theoretically possible; direct analysis of meteorites & lunar
samples reveals what has actually happened in nonliving environment
Formation of Polymers
Aggregation & Organization
Early Metabolism
Oxygen
Early presence of life
Speciation
Phyletic Speciation
Pollen Transfer
carry one full haploid genome & al alleles of plant
wind, animal, birds contribute to distribute pollen
Seed Dispersal
fruits & seeds of some plant fall close to their parents
seeds are carried by wind, flood, stream feather of migratory birds
but many species have long distance dispersal mechanisms
Vegetative Propagation
if a species produces small, mobile pieces that reproduces vegetatively
Divergent Speciation
Abiological Reproductive Barriers
any physical, non-living features
allopatric or geographic speciation
the original species is physically divided into 2 or more population that cannot interbreed
that prevents two population from exchanging genes
Biological Reproductive Barriers
any biological process that prevents successful gene flow
sympatric speciation
when two group become reproductively isolated even though they grow together
prezygyotic isolation mechanism
he prevention of pollen transfer from on e plant to another which result neither pollination nor fertilization
unique characteristic in alleles, do not allow two population to interbreed
hybrid sterility is one of the earliest post zygotic barriers
Adaptive Radiation
special cap of divergent speciation
a species rapidly diverges into many new species over an extremely shotrt time
genetic drift- the gene pool can change rapidly and erratically
Convergent Evolution
if two distinct, unrelated species occupy the same or similar natural selection may favor the same phenotypes in each. as a result, two may evolve to the point that they resemble each other strongly and are said to be undergone convergent evolution
it is a process to evolve new species by natural selection
