Unit 2 Flashcards
- What is evolution? What is fitness? What is natural selection? Artificial selection? Define stabilizing, directional, and disruptive selection.
Evolution- change in allele frequency over time
Fitness- the ability of an individual to reproduce
Natural selection- the selection of favorable traits by natural selection pressures
stabilizing selection- Favors average traits (bell curve gets taller and narrower)
directional selection- Selection pressure favors one extreme (bell curve shift)
disruptive (diversifying) selection- Selectional pressure favors both extremes (non-normal distribution)
- How does genetic variation arise in natural populations? List the ways. What are the main types of mutations? What are gene interactions? Epistasis? Sexual recombination? Gene flow? Why is genetic variation important in natural populations? What is heterozygote advantage?
Natural selection, genetic drift, gene flow, nonrandom mating
Mutations- point mutations, chromosomal mutations
Gene interactions- The presence or absence of certain genes affect how others are expressed
Epistasis- the interaction of genes that are not alleles, in particular the suppression of the effect of one such gene by another
Sexual recombination- Produces new genetic variation rapidly where mutation does so very slowly (multiplies the level of variation)
Gene flow- individuals moving in from another pop.
Heterozygote advantage- heterozygotes are less prone to harmful recessive hereditary disorders
- What is Hardy-Weinberg equilibrium? What are the major assumptions of H-W equilibrium? If deviating from H-W, what might be happening in the population?
States that genetic equilibrium will be reached if the frequencies of alleles remain stable from one generation to the next = no evolution is occuring
Assumptions
1. No input of new copies of alleles from gene flow or mutation
2. All individuals contribute equal number of gametes
3. large population
4. random mating
5. No natural selection
If deviation, any of the above may happen
p^2 +2pq +q^2 = 1
- How do we quantify genetic diversity? What is heterozygosity? How is it computed? What is expected heterozygosity? What is the Polymorphism or P?
Randomly sample population, Use some genetic technique to assess variation across multiple gene loci i.e. microsatellites (SSR) or SNPs (single nucleotide polymorphism)
Polymorphism (P) – proportion of or percentage of genes that are polymorphic
Gene is polymorphic if most common allele is less than some arbitrary threshold (monomorphic if 95% of individuals have that allele or polymorphic if greater than 5% have that allele)
Heterozygosity- (Ho or H) – can be computed at the individual or pop
Ind= proportion or percentage of genes at which the individual is heterozygous
Pop – proportion of genes at which the average individual is heterozygous
Mean observed heterozygosity – taking the average heterozygosity of all individuals sampled
Expected heterozygosity (He) – determined from Hardy-Weinberg equation (2pq)
- What is phenotypic plasticity? What is a reaction norm? What is genotype-environment interaction? What is a reciprocal transplant experiment and why are they performed? What types of studies are done to determine whether or not differences among populations/groups are plastic responses to the environment or genetic differences?
Phenotypic plasticity- Range of phenotypes that can be expressed without genetic change, such as when exposed to different environments
Reaction norm- Quantitative relationship between phenotypic variables and environmental variables is called the reaction norm
Genotype-environment interaction – The variation in sensitivities of individuals different genotypes to the variation in the environment
reciprocal transplant experiment- individuals in one environment are moved to another environment, to see if an observed trait is due to genetic variation or phenotypic plasticity
- How does natural selection affect allele frequencies in populations? What is fitness? w? s?
Natural selection decreases variation, favors one allele frequency over another
Fitness- defined as the relative contribution an individual makes to the next generation. When s = 1, selection prevents all individuals with that genotype from reproducing.
w- is called relative fitness, w = 1 – s;
s- selection coefficient- a measure of the degree to which selection acts against a particular genotype. The higher the value of s, the more intense the selection.
- What is meant by allopatric speciation, sympatric speciation and parapatric speciation?
Allopatric- speciation while forming species live in the same range
Sympatric- speciation from a common ancestor in separate ranges
parapatric- speciation from a common ancestor with partly overlapping ranges
- What role does phylogenetics play in study of evolution? What is a phylogenetic tree? What can a phylogenetic tree tell us about evolutionary history in a group?
Phylogenetic tree- The phylogenetic tree represents the simplest paths through which related species may have descended from common ancestry.
What can it tell us- It can tell us what a common progenitor to two species may have been. It generally is assumed that species with a more recent comment progenitor are more genetically similar
- What are some of the processes that diminish genetic variation in a population? What is a bottleneck? Genetic drift? Founder event? What role do these play in reducing genetic variation in a population? Could you estimate the amount of genetic variation remaining given one of these processes? What is effective population size and why is it used?
Bottleneck- population is greatly reduced to a few individuals. New pop represents small pop’s genetics
Genetic drift- Random change in allele frequency found in small pops
Founder event – New population is created by a few individuals
could you estimate… yes [1- {1/(2N)}]t
Effective pop size (Ne)- The individuals in a pop that are capable of reproduction it is used because: 1) unequal numbers of males and females 2) differential reproductive success among individuals. 3) fluctuations in population size all contribute to not all individuals contributing equally to the population
What is inbreeding? What is inbreeding depression? What role does inbreeding play in lowering heterozygosity in a population? Can you compute inbreeding coefficient?
Inbreeding- When close relatives mate
Inbreeding depression- adverse effects caused by an Increase in homozygosity
Inbreeding coefficient = F = the probability that 2 copies of the same allele are identical by descent or derived from common ancestor.
F = (He– H) / He, He = 2pq, H= actual frequency of heterozygotes in population. When F = 0, no inbreeding occurs. When = 1, total inbreeding
- What are life histories? What is life history evolution? Define the following terms (major life history traits): maturity, parity, fecundity, and longevity.
Life histories- the schedule of an organism’s life (maturity, death, repro, etc)
Life history evolution- has led to a variety of different strategies (i.e. r and K strategies)
fecundity- the amount of offspring per repro episode
parity- number of repro episodes (Semelparity [single] v Iteroparity [multiple])
maturity- age and size at first reproduction
longevity- how long an organism lives
- Why can’t an organism maximize all aspects of its reproduction? What are the limiting factors?
Limited time, energy and nutrients
- Life history schedules are resolutions of what four major reproductive considerations?
- When to begin reproducing (what age)?
- How many offspring to have at a time?
- How many reproductive episodes before death?
- How much care to bestow upon young?
- What is allocation? What are trade-offs? What are some of the trade-offs that you might expect in nature?
Allocation- Organisms cannot simultaneously maximize all aspects of life’s functions, instead allocation represents a compromise between competing demands.
Trade-off- every modification in one area could mean a decrease in another. Ex body maintenance, growth or reproduction
- Who was David Lack? What role did he play in life-history research? What was his major research finding?
David- a colleague of Moreaus, made life-history study a science
- First to equate fitness to reproductive success
- Fist to document that life histories were tied to specific environments
- Developed a testable hypothesis: suggested that food supply limits the # of offspring that a parent can rear- making clutch size stable
