Energy flows from the sun in the form of sunlight. While sunlight feels good on our skin, it doesn't feed our bellies. When we eat, we are in a way eating part sunshine. When we and other animals produce waste and eventually die, other, mostly microscopic, organisms may use the energy in our waste and dead bodies. This matter is reduced by decomposers and returned to the soil, where it may be used again by plants.
Energy is lost as it flows through an ecosystem.
Some of it is wasted. Likewise, when mammals digest food they convert some of it to heat, which is irretrievably lost to the universe. Matter, on the other hand, is conserved and recycled. Due to the variability of computers, page sizes may vary. Illustration of Crater's ecosystem without plants and animals Switch transparencies and do the same with Figure 2.