PLANT GEOGRAPHY - Discovering Physical Geography - page 235

Ecosystems and Biogeography

part of the system, which sets the environmental context for all
the living organisms in the area. An excellent example of an
abiotic factor is the climate of a particular region, or the types
of rocks and minerals found in a specific place, to name but two.
As far as the living things are concerned within an
ecosystem, biogeographers may first consider the role of
autotrophs , which are organisms that make their own food
from light energy or chemical energy without eating. Although
phytoplankton and some bacteria are autotrophs, the most im-
portant self-feeding species are plants. Yet a third component of
an ecosystem, heterotrophs , are animals that consume plants
or other animals for survival. Heterotrophs, of course, are sub-
divided into three categories, including herbivores that feed on
plants, carnivores that eat other animals, and omnivores, which
consume both plants and animals.
The final component of any ecosystem is made up of
decomposers , which feed on dead plant and animal material.

Recall from Chapter 1 that one of the subdisciplines of physi-
cal geography is biogeography . Biogeography examines the
geographical distributions of organisms, their habitats, and the
environmental or historical factors that produce them. As a re-
sult, biogeography is very closely related to ecology and thus
focuses a great deal on ecosystems , which are communities of
organisms that interact in interdependent ways (Figure 10.1).
On a broad scale, the organisms within a particular land ecosys-
tem can range from the smallest microbe living within the soil
to the complex animals that roam the landscape. Ecosystems
are not just confined to terrestrial settings, however, as they also
occur within marine environments.
When considering the nature of any particular ecosystem,
biogeographers often try to understand its various components.
One important factor in an ecosystem is the abiotic or nonliving

Figure 10.1 Components of a forest ecosystem in northern North America. Grizzly bears
hunt for salmon along a stream in Alaska. What are the various components of this ecosystem,
and how do they fit together within a holistic perspective?

Ecosystems A community of plants, animals, and micro-
organisms linked by energy and nutrient flows.

Heterotrophs Organisms that consume complex organic sub-
stances for food.

Autotrophs Organisms that synthesize their own food using
heat or light as the source of energy.

Decomposers Organisms that consume dead or decaying
organic substances for nutrition.