When biologists talk about a population of organisms, they are referring to .

the answer is biomass or biopopulation

Explanation:

when someone talks about a population, they are talking specifically of humans living within a set area. If someone is talking about the organisms living in an area, they are speaking of living things within a set area. bio- meaning life and mass- meaning density of. density is not always speaking of weight. it could also mean how full. biomass means the amount of living organisms within a set area.

heat from the core of the earth causes convection currents to occur in the mantle. these currents slowly move the crust around.