Chapter 8 Quiz

. Imagine a widely distributed mammal species for which body size shows strong heritability and follows Bergmann's rule. Predict the outcome if efficient predators that live in warm regions preferentially attack large individuals.

Evolution of smaller body sizes across the entire range

Evolution of larger body sizes across the entire range

Evolution of a cline, with large bodied individuals in the south and small bodied individuals in the north

Evolution of a cline, with large bodied individuals in the north and small bodied individuals in the south

Extinction of the mammal, as too many stresses cannot be handled at once

. What is most likely to increase rates of gene flow for a benthic (bottom dwelling) marine invertebrate?

Increased lifespan of planktonic larvae

Greater maximum age reached by adults

Expansion of territory size defended by breeding males

Stronger natural selection for camouflage color patterns

An expansion in the breadth of diet

. A population of finches on an oceanic island varies at a particular gene locus. The current allele frequency is A₁ = 40%, A₂ = 60%, and there are 12,000 birds on the island. On the nearest continental mainland, the same species is monomorphic for allele A₁. If 3,000 birds migrate from the mainland to the island, by how much will the frequency of allele A₁ change on the island?

0.08

0.12

0.15

0.45

0.48

. Which condition would result in the least evolution as a result of gene flow?

Unusually high migration variance

A great dispersal distance between birth and mating

Individuals that are very successful at migrating to new populations, but cannot mate in the new locations

Migration rates that vary greatly from year to year

Very different allele frequencies in different subpopulations

. Which is the best explanation for what F_ST represents?

The fraction of genetic variance in a group of populations that results from differences between them

A direct estimation of isolation-by-distance

The variance of gene frequencies within a population compared to the variance of gene frequencies in another population

The fraction of individuals in a population that arrives from another population in each generation

The average distance between the birthplaces of a parent and its offspring

. You observe a very narrow cline in the middle of a broadly distributed species' range. From this you could conclude that

selection is strong.

migration variance is high.

migration variance is low.

Either a or b

Either a or c

. In which situation will gene swamping prevent local adaptation?

Selection is strong and migration is low.

Gene flow is high and the patch favoring the alternative allele is small.

Selection and migration are both very high in magnitude.

Selection and migration are both very low in magnitude.

The adaptive trait varies quantitatively and is controlled by several gene loci.

. Which scenario would be found in a tension zone of a cline?

Natural selection eliminates heterozygotes, preventing introgression deep into the other side of the cline.

There are differing selection pressures on either side of the cline.

There is strong gene flow, relative to selection.

Selection is weak but the cline is maintained by low dispersal rates.

Local adaptation has led to a very low F_ST between either end of the cline.

. Populations of the Florida panther were reduced to very low levels in the second half of the twentieth century. In 1968 Alligator Alley, an extension of a major highway, divided the population into a northern and southern population. If we assume evolutionary equilibrium (and no selection), estimate the N_e of the population to be 75 individuals on either side of the highway, and measure an F_ST of 0.30, what can we conclude about the effect of the highway?

The highway completely isolates the southern population, allowing no gene flow.

The highway is not a barrier to the cats at all, and the regions north and south of the highway act as a single, well-mixed population.

The highway only hinders migration a little bit and gene flow is maintained at a relatively high rate.

The highway severely blocks the southern population, allowing only a tiny amount of gene flow.

The environment has been divided into subregions too small to support large numbers of territorial cats.

. Predict the F_ST of a population that has been split in two by a vicariance event that evenly divided it into two populations of 2,500 individuals if the migration rate is 0.01%.

0.00025

0.2

0.235

0.9615

4

. The product N_e m is equal to the

migration variance.

average distance between the birthplace of parent and offspring.

number of migrants that arrive in a population in a generation.

width of a cline when selection and gene flow work against each other.

change in allele frequency in a population as a result of gene flow.

. Refer to the graph. Ten variable loci were found in an island population of an organism. F_ST was calculated for each to compare with the mainland population.

What can we conclude from the data?

Most loci have low F_ST, so there is probably not high migration between popualtions.

All of the loci have undergone a high rate of adaptive evolution.

Since the population is isolated, genetic drift has led to great differences when compared to the mainland.

Locus D shows signs of local adaptation because of its relatively high F_ST.

Locus I shows signs of high migration because of its relatively low F_ST.

. Which organism depends most on high rates of dispersal and migration for survival of its population?

An annual wildflower that colonizes disturbed patches

An insect that depends on a very specific flower for nectar meals

A freshwater fish that lives in an ancient lake

An island population of bats

A domesticated animal, like a cow or a sheep

. Which factor is least likely to limit dispersal to a new range of an organism whose environment is changing?

The rea of suitable habitat has decreased outside of original range.

Impassable barriers to movement exist.

Organism is physiologically incapable of surviving elsewhere.

Organism is a relatively poor disperser.

Organism has a generalist diet and can find food in many habitats.

. Many North American animal species migrated to the south during Pleistocene ice ages and returned to the north during interglacial periods. These observations are consistent with

expanded physiological tolerance.

distribution shift and habitat tracking.

migration barriers.

range expansion by adaptation.

declining habitat size.

Chapter 8 Quiz

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