Unicellular organisms carry out all the necessary life processes in one cell. in multicellular organisms, each cell is specialized to perform a specific function. how do the cells in multicellular organisms become specialized? a. a single nucleus coordinates the function performed by each cell. b. cells develop specific functions through the expression of different genes as they mature. c. the brain communicates the function required for each cell. d. each cell carries a unique set of genes

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 of the following produces carbon dioxide? a. plants b. animals c. decomposers d. all of the above

Restless tectonic plates move (shift) between one and fifteen centimeters per year month day minute