Which step in the nitrogen cycle is responsible for returning fixed nitrogen back into the atmosphere?

When organisms convert from of energy, what usually results

Which of the following examples can cause gene flow between populations? a.an increase in predators to a population of zebra b.a volcanic eruption that kills half of a population of mice c.bird droppings that contain seeds from a different location d.a person that sprays a toxin on a group of mosquitoes

What is hydroelectric power produced by?