One example is the human body. Our cells, digestive system, teeth and skin provide niches for numerous communities. Bacteria live in our intestines and fungi feed on the dead skin cells in our hair. Many of these organisms are predated upon by others and the principals of ecology can be applied as if they were plants in a forest. The bacteria on human teeth go through a period of succession, with colonisers stabilising the environment, new species moving in and then different species growing on top of these.
Bacteria begin to colonise a clean tooth.
Succession occurs, bacteria grow around eachother.