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King - Evolution Exam One Unit Two
Terms in this set (144)
Who is associated with the concept of mutation?
Thomas Morgan (early 1900's)
What did Morgan believe about mutations?
occur every generation, can occur anywhere in the genome
On a per individual, per gene basis, what are mutations?
incredibly rare (e.g. 0.00000002 mutations per base pair per generation in humans)
Who is associated with the concept of inheritance?
In 1865, Mendel's _____ were published. In the early 1900's, his work was rediscovered and eventually became the _____.
pea experiments, Laws of Mendelian Inheritance
What two major reconciliations did the modern synthesis (1936-1947) include?
1.Mendelian genetics with natural selection and gradual evolution
2. microevolution with macroevolution
How do many alleles interact?
What do allele frequencies not tell you anything about?
What are not all allelic interactions characterized by?
What tells us the expectations for genotype frequencies if no outside forces are acting on the population and also tells us the expectations for allele and genotype frequencies over time if no outside forces are acting on the population?
What are the assumptions of the Hardy-Weinberg Equilibrium?
infinite population size, random mating, no migration, no mutation, no selection
Hardy-Weinberg equilibrium tells us the expectations for genotype frequencies if no outside forces are acting on the population. What is satisfied?
p² + 2pq + q² = 1
Hardy-Weinberg equilibrium tells us the expectations for allele and genotype frequencies over time if no outside forces are acting on the population. What will occur?
If all five assumptions are met, what will not change over time in Hardy-Weinberg equilibrium if no outside forces are acting on the population?
allele and genotype frequencies
Because Hardy-Weinberg equilibrium is a default condition when no outside forces are acting on a population, what is it?
Why is Hardy-Weinberg equilibrium useful?
defining the exact conditions when we expect no change tells us what factors can cause change
Why is Hardy-Weinberg a null model?
evolution is the natural state for populations
What are the evolutionary forces?
selection, mutation, gene flow, genetic drift
Name the evolutionary force associated with the assumption - no selection.
Name the evolutionary force associated with the assumption - no mutation.
Name the evolutionary force associated with the assumption - no migration.
Name the evolutionary force associated with the assumption - infinite population size.
Name the evolutionary force associated with the assumption - random mating.
n/a (only genotype frequencies change, not allele frequencies)
What is the change of allele frequencies due to chance?
What is genetic drift influenced by?
sampling error inherent in the transmission of gametes by individuals in a finite population, other random events that influence the reproductive success of individuals
Regarding genetic drift in natural populations, if a population is very large (e.g. over 1 million individuals) will drift still occur if no other forces are acting?
What are two events that can occur with genetic drift?
bottleneck effect, founder effect
What is allele frequencies in founding populations will be different from source populations due to chance (sampling error)?
What is the ability of an individual to survive and reproduce and is the total contribution of offspring to future generations?
What is the average number of surviving offspring contributed by an individual?
net reproductive rate (R₀)
What is fitness relative compared to?
other individuals in the population (w)
What can relative fitness be measured for?
individuals with a given trait, individuals with a given allele or genotype
What do the fitness effects of an allele depend on?
Selection is the only force that can produce _____ to the environment.
What is a weak mechanism of evolution?
Even very high mutation rates do not produce substantial changes _____.
without other forces acting
How does mutation alone change allele frequencies?
What is mutation critical for?
introducing new alleles for drift and selection to act on
What results from migration of individuals between populations of the same species (movement between populations) and tends to homogenize populations?
What can occur from non-random mating?
What does gene flow counteract?
diversifying effects of drift between populations
What does gene flow increase within populations?
Regarding gene flow, what will counteract the effects of drift?
1 migrant per generation
When can genetic drift prevent fixation of an advantageous allele?
population is small the smaller the population the stronger the effect of drift, selection is weak
What are quantitative traits influenced by?
Because quantitative traits are influenced by the environment, what is one challenge?
quantifying how much phenotypic variation is due to variation in genetic factors and how much is due to variation in the environment
What is the fraction of the total variation in a trait due to variation in genes?
What is the equation for heritability?
VG/VG + VE = VG/VP
What do genes only operate within, therefore, they cannot be disentangled within an individual?
What type of parameter is heritability?
What are the types of heritability?
broad-sense (H²), narrow-sense (h²)
What is the equation for broad-sense (H²) heritability?
H² = VG/VP
What does broad-sense (H²) heritability include?
all genetic effects
What is the equation for narrow-sense (h²) heritability?
h² = VA/VP
What does narrow-sense (h²) heritability include?
only additive genetic effects
Regarding heritability, because alleles are passed on and not genotypes, therefore, what are passed on?
only additive effects
What is measuring heritability based on?
observed and expected resemblance among relatives
What are the means for measuring heritability?
parent-offspring regression, familial relationships, actual genetic similarity compared to phenotypic similarity
In parent-offspring regression, what does the slope of the best fit line equal?
What is the Breeder's equation?
R = h²S
In the Breeder's equation, what is R?
response to selection, change in the mean trait value
In the Breeder's equation, what is h²?
In the Breeder's equation, what is S?
In the Breeder's equation, how do you calculate S?
S = mean(breeders) - mean(population)
How can heritability be estimated from the Breeder's equation?
h² = R/S
The genetic component of quantitative traits can be estimated by looking at the _____. This estimate enables you to predict how a population will respond to _____. The magnitude of the response is directly proportional to the _____ for the trait in question. Quantitative genetics allows you to understand the genetic basis of virtually _____, even if you do not know the specific genes involved.
phenotypic similarity of relatives, selection, heritability, all aspects of the phenotype
Unlike traits determined by a single gene, what do we usually not know for polygenic traits, and what is an example?
exact genes; human height
How many protein coding genes does the human genome contain?
What are the strategies used to determine what genes are involved in a phenotype determined by polygenic traits?
QTL mapping, Genome Wide Association Studies
How does QTL mapping work?
cross two populations more than once to produce recombinants which allows us to associate section in genome with phenotype
How does Genome Wide Association Studies work?
many individuals are sequenced and sections of their genomes are associated to predict phenotype
In selection experiments, what can be directly observed?
process of evolution
Describe how laboratory selection experiments work.
artificial conditions, experimenter decides who reproduces
Describe how selection experiments in nature work.
executed in nature, experimenter introduces organism to new environment and allows evolution to occur naturally
Describe how unintentional selection experiments work.
evolution resulting from selection imposed by humans unintentionally
Are there many or few examples of laboratory selection experiments?
Are there many or few examples of selection experiments in nature?
few (logistical reasons)
What are the methods for studying selection and adaptation?
biology of natural populations (experiments and observational studies), selection experiments, the comparative method, comparison of real organisms with predictions of theoretical models
How does the comparative method work?
compares species (or populations) and tests for patterns across species
What does the comparative method show?
what has happened in past evolution
What is one of the most common methods for studying adaptation?
The comparative method tests for patterns across species including correlations among _____ and correlations between _____ of the environment.
traits, traits and features
Two clades are expected to show _____, and species within clades are expected to be _____ to one another.
differences, more similar
What are all models in biology?
What do models in biology balance?
complexity and realism
What do models in biology tell us?
what happens when the assumptions of the model are met
What are the major forces of evolution?
selection, genetic drift, gene flow
In an isolated population, if there is genetic variation at a locus that is neutral (does not affect fitness), what evolutionary force will cause the most change in allele frequencies at that locus over time?
In an isolated population, if there is genetic variation at a locus that is neutral (does not affect fitness), the evolutionary force that will cause the most change in allele frequencies at that locus over time is genetic drift. In the absence of new mutations, which of the following would you expect to happen over time at this locus?
one allele would eventually go to fixation in the population
Why is genetic drift important when there is a founder effect or a bottleneck effect, and do you need one of these in order for drift to happen?
helps move the population; no
What is variation in non-coding DNA (including pseudogenes) and variation that does not have large effects on a phenotype?
neutral genetic variation
Regarding neutral genetic variation, what percentage of the human genome codes for proteins?
What does neutral genetic variation include?
Regarding patterns of molecular evolution from genetic drift, what are the two possibilities from a neutral mutation?
loss (more likely), fixation (less likely)
What will influence how long will it take for populations to have fixed differences between them? Will this happen at the same time for all alleles in the genome?
population size and demography, strength of selection, positive or purifying selection, when mutations occur; different alleles will change at different rates
When might it be more likely the gene tree does not match the species tree?
rapid divergence between species, genes that evolve slowly (have long coalescence times relative to species divergence)
What is the process by which, looking back through time, the genealogy of any pair of homologous alleles merges in a common ancestor?
What are homoplasy and reversals more likely to occur at?
molecular level (only 4 possible bases - A, T, G, C)
What are the methods for molecular phylogenetics?
maximum parsimony, distance-matrix methods, maximum likelihood and Bayesian methods
What are procedures for constructing phylogenetic trees by clustering taxa based on the proximity (or distance) between their DNA or protein sequences; these methods place closely related sequences under the same internal branch, and they estimate branch lengths from the observed distances between sequences?
What are approaches used to estimate parameter values for a statistical model; they are used in phylogeny reconstruction to find the tree topologies that are most likely, given a precise model for molecular evolution and a particular data set?
maximum likelihood and Bayesian methods
What do maximum likelihood and Bayesian methods both model and test?
evolutionary process; many possible trees
Do all Homo sapiens populations share recent ancestry?
Regarding all Homo sapiens populations sharing recent ancestry, where are the highest levels of genetic diversity?
in African populations
Regarding all Homo sapiens populations sharing recent ancestry, what are all non-African populations including African populations nested within?
How do we know when things happened?
geological timescale (radiometric dating) is used to date fossils
Regarding expected patterns of molecular evolution from genetic drift, what does the rate of substitution per base pair per generation equal?
rate of mutation
Regarding expected patterns of molecular evolution from genetic drift, what is the probability each mutation goes to fixation in a large population?
Regarding expected patterns of molecular evolution from genetic drift, what is the probability each mutation goes to fixation in a small population?
Regarding expected patterns of molecular evolution from genetic drift, what is the number of mutations that occur each generation in a large population?
Regarding expected patterns of molecular evolution from genetic drift, what is the number of mutations that occur each generation in a small population?
What are the expected patterns of molecular evolution from genetic drift?
constant rate of substitution that is equal to the mutation rate
By viewing genetic drift as a constant rate of substitution that is equal to the mutation rate, what does using molecular traits that change at a steady rate show?
timing and rate of evolution
By viewing genetic drift as a constant rate of substitution that is equal to the mutation rate and using molecular traits that change at a steady rate for timing and rate of evolution, what can be dated?
common ancestor between groups, major evolutionary events (especially useful when the fossil record is poor: e.g. flatworms, viruses)
What is changes at the molecular level accumulate at a constant rate, in which knowing rate and number of changes can determine time?
simple molecular clock model
How may molecular clock rates vary?
from base to base, gene to gene, lineage to lineage
What can affect molecular clock rates?
changing generation times, species-specific differences, change in function of the protein studied, changes in the intensity of natural selection
What can estimates from molecular clock rates be?
What are the expected patterns of molecular evolution from selection?
rapid loss (deleterious mutation) or rapid fixation (beneficial mutation)
If there is a synonymous mutation, is there an expected effect on fitness?
If there is a nonsynonymous mutation, is there an expected effect on fitness?
What are the expectations for molecular evolution if the rate of synonymous to nonsynonymous mutations is the same?
What are the expectations for molecular evolution if there are more nonsynonymous substitutions than synonymous?
What are the expectations for molecular evolution if there are fewer nonsynonymous substitutions than synonymous?
What is the rate of nonsynonymous substitutions per site?
What is the rate of synonymous substitutions per site?
What does it mean when dN/dS < 1?
substitutions are deleterious (purifying)
What does it mean when dN/dS = 1?
substitutions are neutral
What does it mean when dN/dS > 1?
substitutions are advantageous (positive)
What refers to changes in the phenotype produced by a single genotype in different environments?
What may phenotypic plasticity influence?
What is a trait that increases an individual's fitness relative to individuals without that trait?
Is adaptation expected to be common?
Why is adaptation expected to be common?
phenotypic variation is nearly always present, most traits have non-zero heritability, phenotypic variation often correlates with fitness
What are the modes/types of selection?
directional, stabilizing, disruptive
What two points should be remembered about modes/types of selection?
1. selection intensity and direction can change over time
2. responses to selection in the wild can be large causing evolution to be rapid
How do interrelated traits evolve with the focal trait?
morphological changes, behavioral changes, physiological changes
Where are rare alleles mostly found?
What can we explain with a single gene model?
one allele replacing another (after this need mutation), limited range of variation
What are most traits?
What do not conform to discrete categories and do not display usual 3:1, 1:1, or 1:2:1 ratios?
Selection can result in phenotypes _____ of variation, and significant change can occur _____.
outside the original range, rapidly
The limitations of a single gene model: natural selection can only finetune in a _____, further evolutionary change is dependent on _____, and is not consistent with natural selection leading to _____.
limited range, mutation, macroevolution
Selection can result in phenotypes outside the original range of variation, and significant change can occur rapidly. What cannot account for these observations?
single locus model of selection
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