A convecting mantle is an essential feature of plate tectonics and contributes to the formation of both igneous and metamorphic rocks. Where does the thermal energy that drives these convection currents come from?
A) The convection of the mantle is driven by the heat gradient within the mantle layer itself.
B) The convection of the mantle is a product of the transfer of heat from the core to the lower mantle.
C) The convection of the mantle is the result of the radioactive decay of nickel occurring within the core.
D) The heat is the frictional heat from the rotating fluids within the core of the Earth which rises up into the mantle.

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.

Which situation is an example of not doing work? lifting a couch throwing a baseball running up stairs carrying a box

Which of th following best describes how genes produce traits in an organism?