Sexual selection favors individuals with traits that increase their ability to obtain mates, such as mating calls in crickets. Using this example, propose a scenario where sexual selection could contribute to divergence in sympatric speciation.

Bird guides once listed the myrtle warbler and Audubon's warbler as distinct species that lived side by side in parts of their ranges. However, recent books show them as eastern and western forms of a single species, the yellow-rumped warbler. Most likely, it has been found that these two kinds of warblersa. live in similar habitats and eat similar foods.b. interbreed often in nature, and the offspring are viable and fertile.c. are almost identical in appearance.d. have many genes in common.

When the ranges of two different species meet, a stable 'hybrid zone' occupied by hybrid individuals may form. How is this possible?a. Two diverged populations are capable of mating and producing viable and fertile offspring.b. Hybrid individuals are always allopolyploid and are thus unable to mate with either of the original species.c. Hybrid individuals may have reduced fitness and thus be strongly selected against.d. One species has a selective advantage, so as hybridization continues, the other species will go extinct.

For two populations of organisms to be considered separate biological species, they must be .a. reproductively isolated from each other;b. unable to produce living offspring;c. physically very different from each other;d. A and C are correct;e. A, B, and C are correct

Which of the following is an example of a postzygotic reproductive barrier?a. One Ceanothus shrub lives on acid soil, another on alkaline soil.b. Mallard and pintail ducks mate at different times of year.c. Two species of leopard frogs have different mating calls.d. Hybrid offspring of two species of jimsonweeds always die before reproducing.

Explain how molecular chaperones facilitate protein folding in many different polypeptides, each with their own specific shape.

Cells that line your intestines are known to possess a large number of membrane proteins that transport small molecules and ions across the plasma membrane. Which of the following cell structures would you expect to be required for this characteristic of the cells?a. the endoplasmic reticulumb. peroxisomesc. lysosomesd. the cell wall

The biological definition of 'race' corresponds to all of the following except:a. the genealogical species concept;b. the idea that subgroups within the same species can be distinguished from each other by ancestry;c. there is a natural hierarchy of groups within a species from 'lowest' to 'highest' forms;d. it should be possible to identify races on the basis of shared allele frequencies among populations;e. races within a species are not reproductively isolated from each other.

Biologists have found more than 500 species of fruit flies on the various Hawaiian Islands, all apparently descended from a single ancestor species. This example illustratesa. polyploidy.b. temporal isolation.c. adaptive radiation.d. sympatric speciation.