Please enable JavaScript.
Coggle requires JavaScript to display documents.
Population Genetics and Evolution (Factors that cause gene pool to change,…
Population Genetics and Evolution
Population genetics
Abundance of different alleles within a population
Increases, decreases, or remains the same with time
Gene pool
Total number of all alleles in all sex cells
Individual of a population
10 billion haploid sex cells
Factors that cause gene pool to change
Mutation
Existing alleles decrease
New alleles increase
Depends on pop. size
Accidents
Organisms that cannot adapt
Volcanic eruptions
Flood, hailstorms, drought
All indiv. in affected areas killed
Natural bodies act as selective forces
A fire near the west Texas town of Fort Davis damaged many trees, shrubs and succulents but seemed to only kill a few. These plants are
Dasylirion leiophyllum
and although all were burned severely, many survived. However, other were killed completely. If the ones that survived differed genetically from those that died then the fire was a selective force. The gene pool after the fire will be different from what it was before the fire.
Artificial Selection
#
Humans purposefully change the allele frequency in a gene pool
Selective breeding of crop plants and domestic animals
Desired qualities
Natural selection
#
Survival of the fittest
Most adapted to environment survive
Pop. must produce more offspring that can grow and survive to maturity in that habitat
Progeny must differ from each other in their types of alleles.
Competition for water and nutrients among crowded root systems
Can only act on preexisting alleles
Rates of evolution
Most pop. are well adapted to environ. or else they wouldn't exist
Few mutations produce new phenotypes
Many species of seedless plants; ferns that for tens of millions of years have not diverged into a new species
Plants of
Equisetum
have jointed stems. Originated millions of years ago and had many species at one time, most of which are extinct. There are now only 15 species of living plants. Even though many are widespread and well adapted to many areas, they do not appear to be involving into a new species.
Studies of evolution
Changes in gross structures
Flowers, leaves, shoots, fruits, and trichomes
Evolution
Change of nucleotide sequences in a species DNA through Natural selection
Genetic drift
Accident
Speciation
Phyletic
One species gradually becomes so changed that
it must be considered a new species
Millions of years often required
Divergent
Some popul. of a species evolve into a new second species
Other popul. either continue relatively unchanged, as the original parental species or involve into a new third species
Gene flow
Pollen transfer
Pollen grains each carry one full haploid genome
All alleles of a plant are present in it's pollen grains
New alleles can move to distant plants
Birds spread pollen
Can be rapid
Movement of alleles through space
Seed dispersal
Carried by wind, floods, stream flow
Islands by rafting
Fur or feathers of animals
Vegetative propagation
Small mobile pieces that reproduce vegetatively by a species
Reproductively isolated
#
Abiological
Any physical, nonliving feature that prevents two populations from exchanging genes
Original species is physically divided into two or more populations that cannot interbreed
Allopatric
Geographic speciation
Biological reproductive barriers
Any biological phenomenon that prevents successful gene flow
Flower color, shape, or fragrance
Sympatric speciation
Chemosynthesis
Known chemical and physical processes rejecting all traces of divine intervention
Before origin of life the surface of earth was different than what it is now and the chemical present could then react spontaneously
Producing more complex chemicals that could in turn continue to react
Apparatus used by S.Miller to show that the first steps in the chemosynthetic origin of life were possible
Plants exposed to mutagens
Natural selection leads to Evolution
Range do not meet
