There are a number of classical areas of interest in ecology, and they revolve around questions similar to the following: how much is the photosynthesis of a hectare of land? How many animals of what types might that photosynthesis be able to support as a base for their food resources? How many species might “divide up” the land or food resources available? How do the species present change as the physical conditions change, for example as one ascends a mountain? What is the proportion of food that is passed on from each food or “trophic” level to the next? What are the mechanisms that control the populations, communities and ecosystems in some area? How are human activities impacting these natural systems?