Organisms do not exist in isolation. In fact, they depend on other organisms AND also nonliving things. These interactions are necessary for life to exist and we notice that, in nature, a change in one population affects other populations in an ecosystem. This is something that can lead to interesting consequences.
This section is an introduction to the principles of ecology. We look at these principles from the level of the individual organisms all the way up to the biosphere. We start of by talking about what ecology actually is and end by talking about the different types of living relationships that exist between species.
This is section 2.1 in the Book Biology: The Dynamics of Life.