1. The correct answer is the first option: energy flows in one direction, adnd nutrients recycle. Think of a fly. When a fly is eaten by a frog, the energy from the fly goes into the frog. When the frog is eaten by a larger animal, then the energy from the frog goes into the larger animal. It's never the other way around (the energy from the larger animal doesn't go into the consumed frog, and the energy from the frog doesn't go into the consumed fly). However, the nutrients from these insects and animals are recycled, because the larger animal can use nutrients from both the frog and the fly. 2. The correct answer is nitrogen fixation. Nitrogen fixation is a chemical process in which nitrogen from the atmosphere is converted into organic compounds. This usually occurs with the help of certain microorganisms, which are bacteria. 3. The correct answer is the third option. Something is organic simply when carbon is covalently bonded to the atoms of other elements, a process which certain living organisms are able to do. 4. The correct answer is the third option. Biogeochemical cycling is a type of pathway that allows chemical substances to move through different spheres. This is why our actions on earth affect things like the atmosphere (for example the use of hairspray, and how it adds to the deterioration of the ozone layer).
