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Population Genetics and Evolution (Evolution and the Origin of Life…
Population Genetics and Evolution
Population Genetics
Situations in which Natural Selection Does Not Operate
No adaptation if population is has the same genetics
If survival is universal, natural selection does not occur
Multiple Selection Pressures
Mutations that produce alleles that result in improved fitness
Insects, droughts, & the cold impact the plant
Factors that Cause the Gene Pool to Change
Natural Selection
Survival of the fittest
Does not always result from an agent outside the organism
Accidents
Ex: Volcanoes that produce poisonous gases and molten rock
Events to which organisms cannot adapt
Artificial Selection
Carried out in conjunction with artificial mutation
Humans purposely change the allele frequency of the gene pool
Factors that Are Not Part of Natural Selection
Only humans and other primates act with purpose and intent
Natural Selection doesn't include purpose, planning, intention, or voluntary decision making
Mutation
Existing alleles decrease in frequency
Population size determines significance of mutation
Rates of Evolution
Evolutionary changes can occur quickly
Certain alleles are hard to identify unless they result in a identifiable effect on the phenotype
Most populations are well adapted to their habitat
Speciation
Divergent Speciation
Abiological Reproductive Barriers
Allopatric or geographic speciation
Original divided into multiple populations that can't interbreed
Biological Reproductive Barriers
Mutations
Environmental diversity
Adaptive Radiation
Species diverges into many species in a short amount of time
founder individuals: gene pool
Convergent Speciation
Two distinct species in the same habitat
morph to look the same
Only phenotypes converge
Phyletic Speciation
Vegetative Propagation
Contribute to gene flow
Alleles that arise at different geographic sites come together through gene flow
Seed Dispersal
Many species have long- distance dispersal methods
Seeds can be moved by animals, or the weather
Pollen Transfer
1 full haploid genome
Alleles present in pollen grains
Evolution and the Origin of Life
Aggregation and Organization
1st aggregation controlled by solubility
Equilibrium between formation and distruction
Early Metabolism
Metabolic pathway, two steps, two enzymes
Glycolysis evolved early
Formation of Polymers
Require high concentrations of monomers
Polymerization reactions occur with heat/warmth
Chemicals Produced Chemosynthetically
Oparin and Haldane, S. Miller
What is theoretically possible
Oxygen
Oxidizing Atmosphere
Oxygen went from a dangerous pollutant to a valuable resource
Conditions on Earth Before the Origin of Life
Time Available for the Origin of Life
No Limits
No O2 = no decomposition
Energy Sources
Heat and electricity
Volcanoes (produce lightning)
Chemicals Present in the Atmosphere
Second Atmosphere: H2S, NH4, CH4, & H2O
First Atmosphere consisted of Hydrogen
The Presence of Life
Inorganic compounds to living bacteria
Living and nonliving systems are identical
