While energy flows through an
ecosystem and must be constantly supplied, chemical elements are
recycled. As an element moves through an ecosystem, it may cycle
between several different chemical forms.
Not all chemical forms are
usable by all organisms. It is the job of particular organisms in an
ecosystem to convert the chemicals into usable forms.
In this Lesson, we'll look at
the cycling of three important elements for biological organisms:
carbon, nitrogen, and phosphorus. We'll also explore how human
activities are altering the balance of certain chemicals in our