Environmental Engineering Reference
In-Depth Information
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The Science of Ecology
A
SK SOMEONE TO DESCRIBE AN ECOLOGICAL SYSTEM AND YOU MIGHT GET
the response that it is a group of organisms living together in a fixed place.
This is a view likely derived from the familiar elementary school science
experiment in which soil, water, nutrients such as nitrogen, bacteria, worms,
some plants, and perhaps some herbivores such as snails or insects are put
into a hermetically sealed glass container, placed in sunlight, and then left
to their own devices. Observers of this experiment always marvel that this
simple ecosystem is able to maintain itself indefinitely without any kind of
nutrient or species input from the outside.This is because the experiment
does not merely assemble a haphazard collection of species. Rather, the ex-
periment deliberately assembles species that together create a natural econ-
omy involving a chain of production and consumption, albeit of food
energy and nutrients, but an economy nonetheless. In this economy, plants
draw up water and nutrients from the soil and carbon dioxide from the air
and are stimulated by sunlight to convert those different chemicals into tis-
sue; herbivores eat that plant tissue and when old individuals die the chem-
ical constituents of their body are broken down by worms and bacteria and
are recycled back through the system.This economy functions whenever
the important lines of dependency, that is the linkage between consumers
and their resources and the recycling feedbacks, are sustained.
This simple container system is a powerful metaphor for the way species
assemble and interact in nature.The processes of production and consump-
tion are fundamental to sustaining the functioning of all ecological systems
globally. Natural ecological systems differ from the container system in that
they are comprised of vastly more species with many more interdependen-
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