-
Geographic isolation of populations precedes evolution of species-level differences
Allopatric speciation
-
A reproductive community of populations (reproductively isolated from others) that occupies a specific niche in nature
- Mayr's Biological Species Concept
- Note: Also called the isolation species concept
-
Two types of reproductive barriers according to the Biological Species Concept
-
Reproductive barriers in which zygotes are not formed from matings between two species
Prezygotic barriers
-
Reproductive barriers in which two species are able to form a hybrid zygote, but the resulting hybrid is inviable or breaks down.
Postzygotic barriers
-
The concept that selection on hybrids with postzygotic barriers can lead to prezygotic isolation
Reinforcement
-
Problems with the Biological Species Concept
- It applies to sexual forms only
- No temporal dimension
- Not a single unit of evolution
- Often not practically testable
-
Defines a species as a lineage of ancestral-descendant populations diagnosably distinct from other such lineages
Phylogenetic Species Concept
-
Subdividing a formally continuous habitat
Vicariance
-
Rare disposal across a pre-existing barrier
Founder event
-
-
Speciation in which multiple species lineages are generated from an ancestor in an undivided geographic area
Sympatric speciation
-
The idea that evolutionary change occurs in small increments
Gradualism
-
The Ancon sheep example shows that which principle of Darwinian evolution is not always true?
- Gradualism
- Note: Ancon sheep example is an example of a large phenotypic change in a single generation
-
A population-based mechanism of evolutionary change invoked to explain "adaptation"
Natural selection
-
Random component of natural selection
- Variation is produced at random with respect to an organisms needs
- i.e. new mutations are equally likely to be useful as they are to be deleterious
-
Nonrandom component of natural selection
Organisms with favorable traits have higher rates of survival and reproduction, causing populations to accumulate the most favorable variants and discard less favorable ones
-
States that evolution by natural selection has a preset goal or direction; arguments of this sort must be avoided in evolutionary biology
Teleology
-
Characteristics of offspring are correlated with their parents in a population
Heritability
-
Later forms are superior to earlier forms in a general sense
Progressive adaptation
-
A trait that evolved by natural selection for a particular biological role
Adaptation
-
A trait co-opted by natural selection for a role incidental to that trait's origins
- Exaptation
- Ex: bird feathers
-
In creating a mathematical model, you must identify essential aspects of reality and remove distracting elements.
Abstraction and simplification
-
In creating mathematical models, unreal conditions used to facilitate study
Assumptions
-
Three things that mathematical models try to achieve, though often at least one is sacrificed.
- Reality
- Generality
- Precision
-
Replication without mutation
Identity by descent
-
A type of DNA that is useful for study because it does not recombine and is transmitted only by mothers.
Mitochondrial DNA
-
The idea that all copies of homologous DNA trace back to a common ancestral molecule.
Coalescence
-
Newly arising alleles are not predominantly ones advantageous to their possessors
Randomness of mutation
-
Destroys identity by descent
Mutation
-
A set of identical haploid genomes for a specified unit of measurement
Haplotype
-
Definition of haplotype
A set of identical haploid genomes for a specified unit of measurement
-
Organism in which branches of a haplotype tree of chromosome-3 gene orders denote paracentric inversions
Drosophila pseudoobscura
-
A local population of reproducing individuals that has physical continuity over space and time
Deme
-
Characterized by genotype frequencies
Deme
-
The population of gene copies collectively shared by individuals of a deme
Gene pool
-
Population of potential gametes in a deme
Gene pool
-
Characterized by allele frequencies
Deme
-
Hardy-Weinberg Equation
(p^2)+(2pq)+(q^2) = 1
-
Implies that Mendelian traits are NOT expected to show Mendelian ratios in demes
Hardy-Weinberg Equilibrium
-
Mutation rate
(# newly mutate copies) / (total # copies of homologous DNA)
-
When the rate of elimination of a lethal allele (q^2) equals the rate of creation of a lethal allele (mutation rate)
Mutation-selection equilibrium
-
Shows that Mendelian inheritance does not cause evolutionary change
Hardy-Weinberg Equilibrium
-
Hardy-Weinberg equilibrium shows that this does not cause evolutionary change
Mendelian inheritance
-
Assumptions of Hardy-Weinberg Equilibrium
- Population infinitely large
- Random mating
- No mutation
- No migartion
- No natural selection
-
Disease caused by variation at the beta-hemoglobin locus
Sickle cell anemia
-
Two alleles in sickle-cell anemia
-
Disease that can be alleviated by eliminating phenylalanine from the diet
PKU
-
Two diseases which provide good examples of gene/environment relationship in determining phenotype
PKU and Scurvy
-
Analysis of genetic variance for continuously varying phenotypes
Quantitative genetics
-
Set of phenotypes associated with a particular genotype in interaction with a variety of environmental conditions and genetic backgrounds
Norm of reaction
-
Type of inheritance in which a large number of loci contribute to many discrete categories
Polygenic inheritance
-
Numbers of facets in eyes of wild-type and Bar-eyed Drosophila vary widely and largely overlap
Example of environmental variation (the variation is caused by changes in temperature)
-
Average amount by which individuals of a specified genotype differ from the mean value of their population for a quantitative phenotype
Genotypic deviation
-
Calculating genotypic deviation
Mean phenotype of the genotype minus mean phenotype of the population
-
A measure of how much phenotypic variance is associated with genotypic variation in a population in a given generation
Broad-sense heritability
-
A measure of how much phenotypic variance is associated with additive genotypic variation in a population
Narrow-sense heritability
-
The average genotypic deviation caused by a gamete bearing a certain allele after fertilization with a second gamete drawn at random from a gene pool
Average excess of a gamete type
-
Synonym for "breeding value"
Additive genotypic deviation
-
Assigns a "phenotype" to a gamete, the physical basis of the transmission of phenotypes from one generation to the next
Average excess
-
Must be specified to calculate genotypic frequencies from frequencies of alleles in a population
System of mating
-
Sum of the average excesses of the alleles in a genotype
Additive genotypic deviation
-
Variance that can be transmitted through gametes to influence phenotypic variation in the next generation
Additive genetic variance
-
Genetic variance that cannot be transmitted through gametes to influence phenotypic variation in the next generation
Non-additive genetic variance
-
Non-additive genetic variance in a single-locus model
Dominance variance
-
Non-additive genetic variance in a two-or-more-locus model
Epistatic variance and dominance variance
-
Is necessary but not sufficient for dominance variance at the population level
Mendelian dominance
-
Mendelian dominance is necessary but not sufficient for this at the population level
Dominance variance
-
If dominant allele is rare and mating is random:
- All copies are in heterozygous genotypes
- All copies contribute equally to population-level variation
- Genetic variance is additive
-
If dominant allele is common and mating is random:
- Copies occur in both homozygous and heterozygous genotypes
- Copies in heterozygous genotpes contribute twice as much to populational variation as do copies in homozygotes
- Produces some non-additive genetic variance
-
Used to measure heritability without measured genotype approaches
Covariance between parents and offspring
-
Half of the additive genetic variance
Covariance between parents and offspring
-
Standardized covariance that varies from -1 to +1
Correlation coefficient
-
Disease that is genetically transmitted but not heritable
Tay-Sachs Disease
-
HbS allele is necessary but not sufficient for this disease
Sickle cell anemia
-
Often has no discrete alterative categories and no single gene necessary or sufficient to produce it
Heritable phenotype
-
Correlation coefficient between parent and offspring is greater than or less than correlation between siblings?
Less than
-
Relation between correlation between parent and offspring and heritability
Correlation between parent and offspring is equal to half of heritability
-
Locus whose variation contributes to population variation of a continuously varying phenotype
Quantitative Trait Locus (QTL)
-
Saturated, genome-wide linkage maping with SNP markers every 10 cM throughout genome
Genome scan
-
Used in a genome scan to mark an entire genome in 10 cM intervals
SNP
-
Allows genome scans to identify where QTLs occur in a genome but can be misleading in identifying which variable site within a locus actually causes phenotypic variation
Linkage disequilibrium
-
Use haplotype tree to test SNP sites for influence on a disease phenotype
Tree scan
-
Non-additive genetic variance at the population level arising from interactions among genotypes at different loci
Epistatic variance
-
Mendelian epistasis is necessary but not sufficient for this
Epistatic variance
-
This is necessary but not sufficient for epistatic variance
Mendelian epistasis
-
An evolutionary force that causes many small changes
Mutation
-
An evolutionary force due to random changes in allele frequency
Genetic drift
-
An evolutionary force that is associated with finite population size (sampling error)
Genetic drift
-
5 Properties of Genetic Drift
- No Direction
- Cumulative
- Strength is inversely proportional to twice the population size
- Can lead to loss of alleles
- Isolated demes become genetically differentiated
-
Populational parameter that permits SNP markers in a genome scan to identify chromosomal regions that contribute to variation in a quantitative phenotype
Linkage disequilibrium
-
Features substrate neutrality, underlying mindlessness and guaranteed results
Algorithm (Dennett)
-
Helps to reconcile Mendelian heredity and continuously varying phenotypes
Polygenic inheritance
-
Fate of alternative forms of genes or gene combinations over space and time in a reproducing population
Genetic evolution
|
|
