In psychologist Robert Rescorla's classical conditioning experiment, one group of rats experienced a tone just before each of 20 shocks. A second group of rats experienced the same number of tone-shock pairings plus an additional 20 shocks with no tone. Rescorla found that the rats in the first group showed a much stronger conditioned fear response than the rats in the second group. How did Rescorla explain this finding

One gene can influence trait(s). one trait can be determined by gene(s).

To answer this question, researchers studied populations of the dusky salamander (desmognathus ochrophaeus) living on different mountain ranges in the southern appalachian mountains. the researchers tested the reproductive isolation of pairs of salamander populations by leaving one male and one female together and later checking the females for the presence of sperm. four mating combinations were tested for each pair of populations (a and b)—two within the same population (female a with male a and female b with male b) and two between populations (female a with male b and female b with male a). the proportion of successful matings for each mating combination was measured. for example, when all the matings of a particular combination were successful, the researchers gave it a value of 1; when none of the matings were successful, they gave it a value of 0. then the researchers calculated an index of reproductive isolation that ranged from 0 (no isolation) to 2 (full isolation). the reproductive isolation value for two populations is the sum of the proportion of successful matings of each type within populations (aa + bb) minus the sum of the proportion of successful matings of each type between populations (ab + ba). the table provides data for the geographic distances and reproductive isolation values for 27 pairs of dusky salamander populations.

Awave has a wavelength of 15 mm and a frequency of 6 hertz. what is its speed?