Please enable JavaScript.
Coggle requires JavaScript to display documents.
Population Genetics and Evolution (Evolution and the origin of life…
Population Genetics and Evolution
Speciation
Natural selection caused a new species to evolve
Can occur in two fundamental ways:
Phyletic speciation
One species gradually changed enough to be considered a new species
Divergent speciation
Some populations of a species evolve into a new species while other populations stay relatively unchanged
Phyletic speciation
Gene flow
New beneficial alleles arise and are selected for
Spread throughout the entire population
Pollen transfer
Pollen (sperm) has a new allele fertilizes an egg and forms a seed with the new allele
Seed dispersal
Long distance dispersal mechanisms
Wind, floods, stream flow, animals, humans are some examples
Vegetative propagation
Plant produces small, mobile pieces that reproduce vegetatively they contribute to gene flow
Divergent speciation
Reproductively isolated
Allele that arise in one part do not reach individuals in another part
A biological reproductive barriers
abiological reproductive barrier
Non living feature that prevents two populations from exchanging genes
Allopathic or geographic speciation
Original species is physically divided into two or more populations that cannot interbreed
Biological reproductive barriers
Biological reproductive barrier
Biological phenomenon that prevents successful gene flow
Sympatric speciation
Two groups become reproductively isolated even though they grow together
Prezygotic isolation mechanisms
Barriers prevent pollen from moving from one plant to another thus neither pollination nor fertilization occurs
Postsygotic internal isolation barriers
Placed and the two sub populations must be considered separate species
Hybrid sterility
One of the eariest postzygotic barriers to arise
Two populations occasionally interbreed or are artificially cross-pollinated
Hybrid invisibility
If cross-pollinated and alleles from one parent code for a protein in compatibilite with those coded from the other parent
Zygote of embryo dies early
Adaptive radiation
Species rapidly diverges into many new species over a short time ( a few million years)
Founder individuals
Initial gene pool is extremely small
Convergent Evolution
Two may evolve to the point the resemble each other
Evolution and the origin of life
Chemosynthesis
Attempts to model the origin of life using only known chemical and physical processes
Rejects all traces of divine intervention
Conditions of earth before the origin of life
Second atmosphere
Produced by release of gases from the rock matrix composing earth
Reducing atmosphere
Due to lack of molecular oxygen and the presence of powerful reducing agents
Energy sources
Heat
Intense UV and ratiation from the sun
Electricity
Time available for the origin of life
Time available for chemosynthetic origin has no limits
Chemicals produced chemosynthetically
Formation of polymers
Aggregation and organization
Early metabolism
Oxygen
The presence of life
Rates of Evolution
How populations adapt over time to their habitat
Descendants diversify
Evolutionary changes that result in loss of a structure or metabolism can come about quickly
Complexity
Population of Genetics
Population Genetics
Abundance of different alleles within a population
Gene pool
Total number of Alleles in all the individuals of a population
Accidents
Events to which organisms can not adapt
Cause a decrease in alleles in an area
Examples:
Meteorite stricking earth
Volcanic eruptions
Can be small or large events
Mutation
Genomes subjected to a mutagenic factor
Mutations occur continuously
Cause existing alleles to decrease
New alleles increase
Artificial selection
Process which humans purposefully change the allele frequency of the gene pool
Examples:
Selective breeding
Used to produce ornamental plants
Flower more or for a longer time
Often carried out in conjunction with artificial mutation
Natural Selection
Most significant factor causing gene pool changes
Survival of the fittest
Two conditions must be met first:
Population must produce more offspring than can possibly grow/survive
Progeny must differ from each other in their types of alleles
Does not include:
Purpose, intention, planning, or voluntary decision making
