Biotic factors reproduce and die as whole individuals. Physical abiotic factors like temperature, light, heat, and humidity, change according to the topography, altitude, and presence of other biotic and chemical factors in the ecosystem. Now comes the chemical compounds which are the ones that recycle. Chemicals in the ecosystem are looked at as compounds like water, or elements like carbon, nitrogen, sulfur, and oxygen. Each of these is recycled by being transferred from one factor(being biotic or abiotic) to another through different types of processes. This recycling of the one material is called a cycle. Each cycle is studied separately for simplicity, but they never exist as separate processes in nature. This is why we call them the carbon cycle, nitrogen cycle ans so on.