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Speciation: within a population the individuals can make offspring with…
Speciation
: within a population the individuals can make offspring with each other.
Selections
Natural
Selection : agents of evolution adopts population to their environments.
Disruptive
Selection: Intermediates chosen against.E.g. Finches, large and small beaks.
Directional
Selection: Eliminates one extreem in phenotype. E.g. flies
Stabilizing
Selection: Eliminates both extremes from range or phenotypes. Favors Heterozygous.
Does not Change most common phenotype.
Human babies, birth weight.
Heterozygous Advantage
: E.g. Sickle Cell Anemia.
Effects Phenotype directly and genotype indirectly.
Artificial
Selection
Dogs, Horses and Corn.
Sexual
Selection
Negative Frequency Dependent Selection:
Female chooses particular characteristics in males over others
Hardy Weinburg Assumptions
Random Matting
No Selection
No Mutations
No Gene Flow
Large Population
Equation: p^2+ 2pq +q^2 = 1
p^2 = homozygous dominant trait/ phenotype (
population
)
2pq = heterozygous trait/ phenotype (
population
)
q^2 = homozygous recessive trait/ phenotype (
population
)
p+q=1
p = dominant allele
frequency
q = recessive allele
frequency
Evolutionary Forces
Non-Random Matting
Mutation
Gene Flow
Small Population Size
Selection
Genetic Drift:
Random fluctuation in allele frequencies by chance.
Bottleneck Effect
: Loss of genetic variability; reduced population size due to natural disaster, disease or extinction.
Founder Effect
: Rare alleles and combinations of alleles may be enhanced in new populations.
Fitness
: producing viable offspring that survive and they produce viable offspring.
does not indicate health.
HIV
Re-infected by different HIV strains: Gene Flow
Multiple Sexual Encounters:Random Mating
Undergoing ant-viral Chemotherapy: Mutations occur and ossuary in HIV itself.
NO RANDOM MATING IS NOT BEING VIOLATED
Random mating is occurring.
Selection is Occurring
: the individual HIV strands survive the treatments because it contains different strains that resist environmental changes.
Infinite Population Size
: Hiv can infinitely multiply and mutate giving the number of individual strands to be quite high.
Mutations
:
Generates genetic variation
Natural Selection acts on genetic variation.
Biological Species Concept
: produce viable offspring (if they come in contact).
Does not apply to Asexual Reproduction.
Morphology not part of species concept.
Types of Speciation:
Allopatric Speciation:
speciate in different area, geologically isolated. (river divides land)
Sympatric Speciation:
same area; species change and use different resources.
Polyploidy
: most common speciation; how plants speciate.
Autopolypolidy
: all chromosomes arise from same species
Tetrapods: four sets of chromosomes.
Triploids: Sterile, odd number
Alloployploidy
: hybrid; one chromosome from each. sterile, don't air right in meiosis.
Instantaneous Sympatric Speciation
: an individual is dorm reproductively isolated from its own species.
Sympatric Speciation via Destructive Selection - RARE
Speciation Increases; Gene Flow Decreases.
Adaptive Radiation:
species occur with few competitors for resources. E.g. Diversification of Darwin's Finch's
Reproductive Barriers
Barriers that prevent the exchange of genetic information.
Prezygotic Barriers:
prevent the proper forming of zygotes.
Environmental
Habitat/Ecological Isolation:
same area, different habitats, rarely interact. E.g. lions and tigers; oak trees.
Behavioral Isolation
: Birds having unique mating songs. Pheromones: chemical signals.
Temporal Isolation
: species produce at different times of day or year. E.g. Wild Lettuce and Frogs
Mating
Mechanical Isolation:
Structural difference that prevents mating. E.g Bees and Pollen.
Gametic Isolation:
gametes form but can't function into the reproductive tract.
Post Zygotic Barriers:
prevents proper functioning of zygotes after they form.
Reduced Hybrid Viability
: zygotes fail to develop or fail to reach sexual maturity.
Reduced Hybrid Fertility
: Hybrid lives but is sterile.
Hybrid Break Down
: Offspring of hybrids have reduced viability and fertility.
Hybrids
Reinforcement
: completely reproductively isolated.
The Pace of Evolution
Gradualism
: evolutionary change occurs slowly through time and is not linked to speciation.
Punctuated Equilibrium:
requires that phenotype change occurs in bursts associated with speciation, separated by long periods of little to no change.
Stasis
: No evolutionary change
Combination of oscillating and stabilizing selection
Species' ability to shift ranges. (ice age, move to water area)
Microevolution
: changes in the gene pool of a population over time which result in relatively small changes (smaller evolutionary changes in allele frequencies within a species) would not result in new species.
Macroevolution:
refers to changes (genetic, morphology, taxonomy, ecology, and behavior of organisms) in organisms, which is significant enough that over time new organisms will speciate. Ancestors can't meet with dependents.