Answer:
While water, carbon, and nitrogen cycle through the ecosystem, energy flows through an ecosystem.
Explanation:
There is a limited amount of water, carbon, and nitrogen in an ecosystem, and therefore, it cycles and passes through an ecosystem multiple times. In the case of energy, however, it is different. Energy goes into a system, flows from organism to organism, and then leaves the system. For example, with water, that water will rain, gather in a river or body of water, and evaporate, doing the cycle over and over again. Energy from the sun however, gets collected by producers, then flows to the organism that eats the plant, then flows to the organism that eats that organism, and so on. The energy does not return to the sun, it just leaves the system (like for example when an organism dies).