DQ 4.12 CH 23

Which of these variables is likely to undergo the largest change in value as the result of a mutation that introduces a brand-new allele into a population's gene pool at a locus that had formerly been fixed?

• average heterozygosity

• nucleotide variability

• geographic variability

• average number of loci

Which statement about the beak size of finches on the island of Daphne Major during prolonged drought is true?

• Each bird evolved a deeper, stronger beak as the drought persisted.

• Each bird's survival was strongly influenced by the depth and strength of its beak as the drought persisted.

• Each bird that survived the drought produced only offspring with deeper, stronger beaks than seen in the previous generation.

• The frequency of the strong-beak alleles increased in each bird as the drought persisted.

Which of the following is a true statement concerning genetic variation?

• It is created by the direct action of natural selection.

• It arises in response to changes in the environment.

• It must be present in a population before natural selection can act upon the population.

• It tends to be reduced by the processes involved when diploid organisms produce gametes

In the formula for determining a population's genotype frequencies, the 2 in the term 2pq is necessary because

• the population is diploid.

• heterozygotes can come about in two ways.

• the population is doubling in number.

• heterozygotes have two alleles.

Evolution

• must happen, due to organisms’ innate desire to survive.

• must happen whenever a population is not well-adapted to its environment.

• can happen whenever any of the conditions for Hardy-Weinberg equilibrium are not met.

• requires the operation of natural selection.

Over time, the movement of people on Earth has steadily increased. This has altered the course of human evolution by increasing

• nonrandom mating.

• geographic isolation.

• genetic drift.

• gene flow.

Adult male humans generally have deeper voices than do adult female humans, which is the direct result of higher levels of testosterone causing growth of the larynx. If the fossil records of apes and humans alike show a trend toward decreasing larynx size in adult females and increasing larynx size in adult males, then

• sexual dimorphism was developing over time in these species.

• intrasexual selection seems to have occurred.

• stabilizing selection was occurring in these species concerning larynx size.

• selection was acting more directly upon genotype than upon phenotype.

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

• artificial selection

• directional selection

• stabilizing selection

• disruptive selection

You are maintaining a small population of fruit flies in the laboratory by transferring the flies to a new culture bottle after each generation. After several generations, you notice that the viability of the flies has decreased greatly. Recognizing that small population size is likely to be linked to decreased viability, the best way to reverse this trend is to

• cross your flies with flies from another lab.

• reduce the number of flies that you transfer at each generation.

• transfer only the largest flies..

• change the temperature at which you rear the flies

Sparrows with average-sized wings survive severe storms better than those with longer or shorter wings, illustrating

• the bottleneck effect.

• disruptive selection.

• frequency-dependent selection.

• stabilizing selection.