Studying how drought affects the food supply in a region of the alaskan tundra would be studying a question at the level of ecological organization.

biosphere

population

community

ecosystem

primary succession occurs in essentially lifeless areas regions in which the soil is incapable of sustaining life as a result of such factors as lava flows, newly formed sand dunes, or rocks left from a retreating glacier. secondary succession occurs

the three components of a nucleotide are the nitrogenous base, the phosphate group and the five-carbon sugar.