Bio 221 Midterm

Front 1

The Hardy-Weinberg equilibrium predicts that the ratios of alleles and genotypes in offspring generation should be the same as in the adult generation if what 5 assumptions are met?

Back 1

1. Very large population

2. Random mating

3. No new mutations

4. No immigration

5. No differential reproductive success

Front 2

The analogy of the "drunkard's walk" refers to:

Back 2

How genetic drift acts randomly due to no selective pressures (selectively neutral), and so an allele is just as likely to increase in frequency as it is to decrease, and given enough time, will eventually reach either fixation or loss (Though it is more likely to reach loss, for example, if it starts out at p=0.2).

Front 3

Genetic Drift: oscillations are relatively larger, and alleles are more rapidly fixed or lost in ______.

Back 3

Small populations

Front 4

The idea of populations having a "flat" distribution of alleles after 2N generations refers to:

Back 4

When enough time is allowed to pass (2N generations), the distribution of alleles in the population will flatten as the proportion of population sin which both A1 and A2are present decreases.

Front 5

In addition to reduction in total number of alleles at particular loci, drift results in:

Back 5

Reduced Heterozygosity (and hence increased Homozygosity)

Front 6

The idea of a bottleneck in genetic drift refers to:

Back 6

Constrictions in population size, followed by subsequent expansions. This causes rarer alleles to be more likely to be lost and reduces genetic variation. Northern Elephant Seals were an example of a bottleneck.

Front 7

The idea of the founder effect in genetic drift refers to:

Back 7

When a new population is started by very few individuals, the alleles represented will usually be the most common ones, but sometimes the random sampling results in the founders having alleles that are relatively rare in the original population. Migrants to Norfolk Island was an example of the founder effect. The founder effect often co-occurs with inbreeding.

Front 8

An individual who is homozygous and with both copies of an allele due to common descent.

Back 8

Autozygous (due to inbreeding)

Front 9

An individual who is heterozygous or homozygous but with alleles NOT due to common descent.

Back 9

Allozygous

Front 10

The fraction of individuals that are autozygous is given by:

Back 10

The inbreeding coefficient F. 0 = no inbreeding, and thus proportion of heterozygotes in a population is given by 2pq (H-W predicted value), but if F > 0, inbreeding is occurring and the proportion of heterozygotes will be less than predicted by H-W.

Front 11

The idea of deleterious alleles refers to:

Back 11

Alleles that negatively affect viability may persist in populations if they are recessive. This is because they are only noticeable when homozygous, which are purged from the population, leaving only heterozygotes possessing the allele. When individuals are forced to be homozygous, a large proportion are deleterious.

Front 12

Therefore, because inbreeding increases homozygosity:

Back 12

Alleles that are recessive and perhaps deleterious can be brought to the surface, resulting in declines in survival or fecundity. Example of King Charles II dying very young due to being the result of many generations of inbreeding in the Hapsburg Dynasty.

Front 13

Fst (fixation index) refers to:

Back 13

The degree of genetic differentiation among populations. A measure of to what extent different populations are fixed for different alleles. Fst = 1 means fixation and therefore no heterozygosity at that locus in that population. Fst = 0 means no variation among populations.

Front 14

Factors that can play into greater fixation include:

Back 14

1. When populations are far apart/separated by geographical barriers

2. Been separated for a long time

3. Members of the species are relatively sedentary

All these things result in less gene flow, and thus greater genetic differentiation between populations over time.

Front 15

The idea that drift towards fixation/loss can be countered by immigration refers to:

Back 15

Even very low rates of immigration can maintain similarity in gene frequency among populations and stop drift. Represents by Nm = number of breeding immigrants per generation needed.

Front 16

Natural selection results in the evolution of adaptations, which can take the form of:

Back 16

Developmental, behavior, chemistry, or morphology.

Front 17

If what things are true, evolution by natural selection will happen automatically?

Back 17

1. Resources are limited and competition is occurring.

2. Individuals vary.

3. Some variants are better than others.

4. These better variants produce more/better offspring or increase survivability to reproducing age.

5. These variations are heritable

Front 18

Absolute fitness refers to:

Back 18

The mean number of offspring produced times the mean survivorship of offspring, the lifetime contribution of individuals of that genotype to population in the next generation.

Front 19

Relative fitness refers to:

Back 19

The comparison of absolute fitness' between competing genotypes. The relative fitness of the most fit genotype = 1, and all other genotype relative fitness' are found by their absolute fitness divided by the absolute fitness of the most fit genotype.

Front 20

The mean fitness of a population, w bar, is highest when:

Back 20

All individuals have the genotype with the greatest relative fitness, which makes w bar = 1.

Front 21

The coefficient of selection (s) refers to:

Back 21

How much less fit one genotype is relative to the fittest genotype. The degree of selective advantage of fittest genotype. The rate of genetic change in a population due to natural selection depends on s and hence relative fitness.

Front 22

Directional selection refers to:

Back 22

The replacement of a less advantageous allele by more advantageous ones.

Front 23

The time for an advantageous allele to reach fixation depends on:

Back 23

1. The initial allele frequencies

2. The selection coefficient

3. Generation time

4. The degree of dominance of the allele (recessive slow to increase but fast to reach fixation, dominant fast to increase but slow to reach fixation, and additive fast at both)

Front 24

Balancing selection refers to:

Back 24

Selection operates in a way that allows genetic diversity to be maintained in a population through either negative frequency-dependent selection, or heterozygote advantage.

Front 25

Negative frequency-dependent selection refers to:

Back 25

When a particular genotype has higher fitness when it is rare than when it is common. Results in a stable equilibrium in population when homozygote frequencies are equal to each other. Example of Dactylorhiza sambucina flower that doesn't reward pollinator with nectar. Bees quickly learn to avoid the common colors, and so rare colors have an advantage.

Front 26

Heterozygote advantage refers to:

Back 26

When the heterozygote has the highest fitness, the population reaches highest mean fitness when A1 and A2 alleles are in stable equilibrium, or stable polymorphism. Example of beta-hemoglobin locus and sickle-cell anemia.

Front 27

Pleiotropy refers to:

Back 27

A mutation that offers one benefit also has negative side effects. Example of the Ester gene in mosquitoes giving resistance to pesticides but reducing survivability against predators. Depending on area, ester gene more common due to pesticide use.

Front 28

Heritability refers to:

Back 28

The proportion of phenotypic variance that is due to genetic variance.

Front 29

Broad-sense heritability refers to:

Back 29

Accounts for genetic and environmental variance.

Front 30

Narrow-sense heritability refers to:

Back 30

The stronger the h2, the more similar the offspring should be to the mean value of their parents. Closer the slope is to 1, the greater the heritability.

Front 31

The Selection Differential, S, refers to:

Back 31

The difference between the mean value of a given trait in successfully reproducing individuals and the mean of all members of the population, including those who don't reproduce. So long as h2 > 0, the larger the selection differential, the faster evolution will occur.

Front 32

The evolutionary response, R, refers to:

Back 32

The speed in which evolution will occur, depending on h2 and S.

Front 33

QTL (Quantitative Trait Loci) Analysis refers to:

Back 33

The process of locating the different genes which control various traits. Requires well-known pedigrees or careful breeding experiments. Once QTLs are found, further studies can work to identify the genes located there, and hence the genes likely influencing the trait. Example of fish with genetic markers and field mice with melatonin mutation (Mc1r).

Front 34

Phenotypic plasticity refers to:

Back 34

When a single genotype has different phenotypes depending on the environment. When there is no modification in a trait depending on the environment, the trait is said to be canalized. Can be polyphenic (two or a few very distinct phenotypes) or continuous.

Front 35

The norm of reaction refers to:

Back 35

The pattern of phenotypic expression by a single gentype across a range of environmental conditions. Example of the nematode worm which showed different reaction norms for fecundity, with strong GxE interactions. When the variation of GxE > 0, evolution can select for the reaction norms that most improves their survival/reproduction. Example of snowshoe hare.

Front 36

i is the measure of:

Back 36

The intensity of directional selection, with i > 0 meaning larger selected for, and i < = meaning smaller.

Front 37

j is the measure of:

Back 37

The change in the range of phenotypic values within a generation, indicating the selection on variance (j), if selection is stabilizing or diversifying. j > 0 means diversifying, j < 0 means stabilizing.

Front 38

Selection gradient refers to:

Back 38

The slope of the relationship between phenotypic value of a trait and the fitness associated with that phenotype as estimated in a regression. The steeper the slope, the stronger the relationship is. Positive if larger values are associated with greater fitness, and negative when smaller values are.

Front 39

Ecological character displacement refers to:

Back 39

Evolution driven by competition for shared resources in which a trait in one or both species evolves to reduce overlap in resource use. Example of the medium vs large finches' beak size, as they both were competing for large seeds. An example of behavioral displacement are the Carolina vs Cuban anoles as they preferred the same height in trees. This led to a related morphological shift for the Carolina anoles who shifted. (Toepad ridges)

Front 40

When three-spined stickleback armored fish invade freshwater, changes in what two different selective pressures act to reduce armor?

Back 40

1. Large bodied predators are rarer in lakes than in oceans.

2. Ions needed for building the bony armor are in lower concentration in freshwater.

Front 41

Homologous sequences separated by specication events are called:

Back 41

Orthologs

Front 42

Homologous sequences separated by duplication events are called:

Back 42

Paralogs

Front 43

The pros of using molecular phylogenetics:

Back 43

1. Molecular data has the potential for vastly larger sets of characters.

2. Recognizing a molecular character state is easy.

Front 44

The cons of using molecular phylogenetics:

Back 44

1. Molecular is restricted to extant or recently extinct taxa.

2. Homoplasy is very common and is difficult to recognize in molecular data.

Front 45

Maximum parsimony refers to:

Back 45

The molecular method of choosing the tree that minimizes the number of changes of character states from ancestral to derived. May involve Bootstrapping, which involves randomly sampling a subset of characters until a parsimonious tree fits those characters.

Front 46

The Neighbor-joining method refers to:

Back 46

Calculating the overall distance between each pair of taxa, and making the tree by joining those taxa with the lowest distance. These trees can be made quickly, but are much less reliable.

Front 47

The Maximum likelihood model refers to:

Back 47

Calculating the probabilities of observing data sets given a tree and the model, and assigning a ML value based on it's likelihood of occurring. The tree with the highest ML value is preferred.

Front 48

The Baysian method refers to:

Back 48

Checking the probability of a tree explaining the model, tweaking it, then checking again, until you maximize the probability.

Front 49

Neutral Variation refers to:

Back 49

Much of genome variation is due to drift rather than natural selection. Neutral mutations should accumulate at a roughly regular rate over time, with a clock-like regularity.

- Also, mutations should accumulate more rapidly in areas of the genome that do not affect an organism's phenotype.

Front 50

The idea of saturation refers to:

Back 50

When using a molecular clock and neutral mutations to find relative ages of species, and a long time has passed since speciation event, the apparent mutation rate in the extant species will be less than what actually took place. Any new mutation overwrite an old one because time between divergence increases.

Front 51

When using neutral theory as a null hypothesis, the number of non-synonymous substitutions vs the number of synonymous substitutions refers to:

Back 51

1. When dN = dS, drift is occurring.

2. When dN > dS, strong positive selection is occurring.

3. When dN < dS, strong purifying selection is occurring.

Front 52

Complex adaptations refer to:

Back 52

Those consisting of modifications to more than one part of the genome that have to work in concert to produce the final phenotypic product. The parts of the genome involved in this include: genes encoding the proteins, and the regulatory elements, together forming a regulatory network.

Front 53

Cis vs trans regulatory elements refers to:

Back 53

1. Cis-acting regulatory elements are those that are located close to the gene they influence, on the same chromosome.

2. Trans-acting regulatory elements are located far from the gene they influence, often on another chromosome.

Front 54

Heterochrony refers to:

Back 54

Evolutionary changes in rate and timing of developmental events. Most examples involve the timing of reproductive maturity changes relative to the timing of overall morphological development. Paedomorphosis: reaching reproductive maturity while retaining many juvenile features.

Front 55

Modularity refers to:

Back 55

The degree to which development of different body structures is independent.

- Highly integrated developmental sequences may not be able to evolve as independent units.

- More modular ones may be freer to respond to natural selection.