The four spheres of the earth.

Energy flows through an ecosystem's living things. Living things also require abiotic factors, like light, water, and oxygen, to survive. Some of these abiotic factors move through an ecosystem in very specific pathways.

The pathways through which this movement occurs are called biogeochemical cycles. But what does this mean? A cycle is any process made of a particular series of steps that always occur in the same order and which are able to repeat over and over. When broken down into parts, the word biogeochemical states exactly what moves through the cycle. Bio- means "life," -geo- means "earth," and -chemical refers to substances or compounds made of elements and molecules. Therefore, biogeochemical cycles are cycles that describe how elements and molecules (sometimes just called matter) move through and between living things and the earth through a series of specific, repeatable steps.

Biogeochemical cycles move through both the abiotic and biotic parts of an ecosystem. Scientists refer to different parts of the earth as different spheres. Each sphere is made of different biotic or abiotic factors, as shown in this image. Hover your mouse over each row to explore the different spheres.

Biogeochemical cycles involve the movement of matter among the four major spheres. Test you knowledge of these spheres by dragging the appropriate term to the blank. Use the image on this screen to help you.