Rangers Rise Set #1

Two populations of a species of squirrel are geographically isolated from each other. Although they have the same population density, one population is significantly larger in number than the other. A new bacterial disease, which is easily spread and extremely virulent, affects both populations at the same time.

Which of the following is the best prediction of how the new disease will affect the two populations?

• The two populations will be equally affected, because the ability to trigger an immune response is randomly distributed among all squirrels of that species.

• The larger population will be less affected by the disease than will the smaller population, because the mutation rate of the larger population is higher than the mutation rate of the smaller population.

• The smaller population will be more affected than will the larger population, because the smaller population has less genetic variation than the larger population has.

• The smaller population will be less affected than will the larger population, because the smaller population exhibits more genetic drift than the larger population exhibits.

Mitochondria are found in most eukaryotic cells and contain their own DNA and ribosomes that are similar to those typical of many prokaryotic cells. Which of the following statements is justified by these observations?

• The mitochondrion is the only location in which eukaryotic cells can synthesize ATP.

• An ancestral cell most likely engulfed an aerobic prokaryotic in a relationship that proved beneficial for both cells.

• Mitochondrial membranes provide abundant surface area for reactions because of the infoldings called cristae.

• The mitochondrion plays a role in respiration, but it also stores the cell's extra mRNA.

Sickle-cell anemia is associated with a mutation in the gene encoding the beta subunit of hemoglobin that results in a change from glutamic acid to valine at position 6. All other amino acids are identical to a normal hemoglobin molecule.

Based on the information above, which of the following mutations is the most likely cause of sickle-cell anemia?

• A single base-pair substitution in the gene encoding the beta subunit.

• A single base-pair insertion in the gene encoding the beta subunit.

• A single base-pair deletionin the gene encoding the beta subunit.

• A translocation of DNA from one chromosome to another.

In the year 2000, specimens of Caulerpa taxifolia, a green alga used in tropical aquariums, were found off the coast of California. Native to the Indian Ocean, C. taxifolia is known for aggressive growth and an ability to compete with sea grasses. It is currently on an international list of invasive species. Which of the following best predicts the consequences of the introduction of C. taxifolia to the California coast.

• Without natural herbivores or competitors C. taxifolia will grow rapidly and crowd out native species of producers.

• C. taxifolia will have a hard time establishing itself because it will have to compete against native species of sea grasses, which are better adapted to the environment.

• C. taxfolia will grow rapidly, leading to an increase in the diversity of producers.

• Because it is not in the Indian Ocean, its natural environment, taxifolia will not be able to grow efficiently.

The graph above represents the number of individuals in a population of wolves and in a population of moose observed in the same isolated geographic area over a 40 year period, from 1955 through 1995. Which of the following statements about the two populations is best supported by the information presented in the graph?

• The reproductive rate of the wolves was greater than the reproductive rate of the moose.

• Mutualism allowed the two populations to reproduce while occupying the same ecological niche.

• Speciation occurred when the two populations became reproductively isolated from each other.

• The wolves were predators of the moose, which were otherwise reproductively successful.

As depicted in the diagram, honeybees communicate the location of flower patches to members of their hives with waggle dances that give information about the direction and distance to the flowers. Which of the following statements about how honeybees communicate the position of flower patches is the most consistent with the model?

• The number of repetitions of the waggle dance indicates the quality of the pollen source.

• The total area covered by any waggle dance leads bees to the target flowers.

• The angle of the waggle phase relative to the vertical plane indicates to the position of the target flowers relative to another beehive.

• The farther the target flowers from the hive, the longer the waggle phase.

Eye pigment in a particular strain of fly is determined by two genes. An autosomal gene that controls the color of the pigments in the eye has two alleles: a dominant allele (R) that results in red eyes and a recessive allele (r) that results in sepia eyes. A sex-linked gene that controls the expression of the colored pigments also has two alleles: a dominant allele (T) that allows for expression of the colored pigments and a recessive allele (t) that does not allow for expression of the colored pigments. Individuals without a T allele have white eyes regardless of the alleles of other eye-color genes.

Which of the following represents a cross between a white-eyed female and a red-eyed male?

• T t X^R X^R x t t X^r Y

• T t X^r X^r x t t X^R Y

• R R X^T X^T x R r X^T Y

• R r X^t X^t x R r X^T Y

Some strains of the bacterium Streptococcus pyogenes secrete poisonous substances called exotoxins. The genes encoding the exotosins are thought to have originated in bacteriophages, which are viruses that infect bacteria.

Which of the following is the most likely mechanism by which the S. pyogenes acquired the ability to produce the exotoxins?

• Bateriophages engulfed cellular debris from dead bacteria.

• Bateriophages in the environment activated bacterial cell division.

• Bacteriophage DNA became integrated in teh bacterial chromosome.

• Bacteriophage proteins were absorbed into bacteria cells by endocytosis.