Bio Mastering #13

Natural selection _____

can favor beneficial mutations

Which of the following is the most predictable outcome of increased gene flow between two populations?

decreased genetic difference between the two populations

Genetic drift occurs in a population. Which of the following statements might be true?

Genetic drift increased the population's fitness. The population was relatively small. Genetic drift decreased the population's fitness. The population experiences a decrease in genetic variation.

An earthquake decimates a ground-squirrel population, killing 98% of the squirrels. The surviving population happens to have broader stripes, on average, than the initial population. If broadness of stripes is genetically determined, what effect has the ground-squirrel population experienced during the earthquake?

a genetic bottleneck

Suppose that a mutation for lactase-persistence occurred in each of the populations described below. In which populations would the mutation be more likely to increase in frequency over time because of natural selection?

a population that raises wheat and sheep

How does the term "lactase persistent" relate to the term "lactose tolerant"?

A lactase-persistent person is lactose tolerant.

Which discovery supports the hypothesis that evolution of the lactase-persistence trait was driven by the use of milk in pastoralist cultures?

Ancient pots used to hold milk are about the same age as the lactase-persistence mutations.

Which of the following statements best summarizes evolution by natural selection as it is viewed today?

Evolution is the differential survival and reproduction of the most-fit phenotypes.

What did researchers discover about the genetic mutation causing lactase persistence?

It is found in a regulatory region (a "switch") upstream of the lactase gene.

How could milk-drinking have provided strong favorable selection for lactase persistence?

Milk may have been a critical food source during times of famine. Milk is protein and fat-rich and therefore could have been an important, high-quality food source. Milk was safer to drink than water and reduced exposure to pathogens.

Which assumption must be correct for a population in Hardy-Weinberg equilibrium for a specific gene?

No genetic drift can affect allele frequencies for the gene.

When nonrandom mating occurs in a population so that individuals prefer to mate with similar individuals, allele frequencies should _____

Remain the same, but homozygotes will be overrepresented in the population

Which statement about balancing selection is correct?

When balancing selection occurs, no single allele has a distinct advantage and thus increases in frequency.

Use the following information to answer the question(s) below. Two populations of birds with somewhat different coloration live on opposite sides of a peninsula. The habitat between the populations is not suitable for these birds. When birds from the two populations are brought together, they produce young whose appearance is intermediate between the two parents. These offspring will breed with each other or with birds from either parent population, and all offspring of these pairings appear intermediate to various degrees. The two populations are _____

different subspecies, under the morphological species concept

The recessive allele that causes phenylketonuria (PKU) is harmful, except when an infant's diet has appropriate levels of the amino acid phenylalanine. What maintains the presence of this harmful allele in a population's gene pool?

diploidy

Which of the following is most likely to produce an African butterfly species in the wild whose populations show two strikingly different color patterns?

disruptive selection

What term is defined as the change in allele frequencies that occurs when a new population is established?

founder effect

The Dunkers are a religious group that moved from Germany to Pennsylvania in the mid-1700s. They do not marry with members outside their own immediate community. Today, the Dunkers are genetically unique and differ in allele frequencies, at many loci, from all other populations including those in their original homeland. Which of the following likely explains the genetic uniqueness of this population?

founder effect and genetic drift

The enzyme lactase breaks the sugar lactose into which compound(s)?

galactose glucose

What does the biological species concept use as the primary criterion for determining species boundaries?

gene flow

Which of the following does not tend to promote speciation?

gene flow

Although each of the following has a better chance of influencing gene frequencies in small populations than in large populations, which one most consistently requires a small population as a precondition for its occurrence?

genetic drift

Which mechanism causes postzygotic reproductive isolation?

hybrid sterility

Which evolutionary mechanism results in adaptation?

natural selection

Heterozygote advantage should be most closely linked to which of the following?

stabilizing selection