3. How can burning fossil fuels affect the nitrogen cycle?

Ibelieve this is the answer:     evolution has no "goal". it is "simply" the survival of the fittest under a given condition. what should be the advantage of living longer? getting kids (=spreading the own genetic information) is done latest until the mid-40s after that we have not much biological meaning.  in addition,  not only does evolution not have a "goal," evolution doesn't necessarily mean "make us better! " it's absolutely possible to evolve negative traits.    hpe i could : )

No animals, as if there are no producers, there's no animals that eat the producers, and no animals that eat those animals, etc.