Why learn about ecology and ecosystems?- Humans and other organisms interact with one another in
ecosystems. - The general type of place where a species lives is its habitat.
The populations of all species in a habitat make up a community. - In all ecosystems there is a flow of energy and a cycling of
materials.
taKe-Home messagebiome The large-scale
community of organisms in
a major ecological setting,
such as a desert.
community The interacting
populations of all species in
a habitat.
ecology The study of the
interactions of organisms
with one another and the
physical environment.
ecosystem One or more
communities of organ-
isms interacting with one
another and their physical
environment through a flow
of energy and a cycling of
materials.
habitat The type of place
where a species normally
lives.
niche The physical, chemi-
cal, and biological condi-
tions a species needs in
order to live and reproduce
in an ecosystem.
succession Sequence in
which the first species to
inhabit an area are then
replaced by others.
n All life on Earth is part of some type of ecosystem.
n Link to Life’s organization 1.3Ecology is the study of the interactions of organisms with
one another and with the physical environment. The gen-
eral type of place in which a species normally lives is its
habitat. For example, muskrats live in a stream habitat,
damselfish in a coral reef habitat. The habitat of any organ-
ism has certain characteristic physical and chemi cal fea-
tures. Every species also interacts with others that occupy
the same habitat. Humans live in “disturbed” habitats,
which we have deliberately altered for purposes such as
agriculture and urban development.
Directly or indirectly, the populations of all species in
a habitat interact with one another as a community. The
large-scale community of organisms in a major ecological
setting such as a desert or coral reef may be called a biome
(Figure 24.1). Different land biomes have different domi-
nant types of vegetation. For example, the plant species of
a tropical rain forest are different from those of a rain forest
in North America.
An ecosystem consists of one or more communities of
organisms interacting with one another and with the phys-
ical environment through a flow of energy and a cycling of
materials. Figure 24.2 shows some typical organisms of an
arctic tundra ecosystem.
A species’ niche (nitch) consists
of the various physical, chemical,
and biological conditions the spe-
cies needs to live and reproduce in
an ecosystem. Examples of those
conditions include the amount of
water, oxygen, and other nutrients
a species needs, the temperature
ranges it can tolerate, the places it
finds food, and the type of food
it consumes. Specialist species have
narrow niches. They may be able
to use only one or a few types of
food or live only in one type of habi-
tat. For example, the red-cockaded
woodpecker builds its nest mainly
in longleaf pines that are at least
75 years old. Humans and house-
flies are examples of generalist spe-
cies with broad niches. Both can live
in a range of habitats and eat many
types of food.
Communities of organisms make
up the biotic, or living, parts of an
ecosystem. New communities may
develop in habitats that were once
empty of life, such as land exposedby a retreating glacier, or in a previously disturbed inhab-
ited area, such as an abandoned pasture. Through a process
called succession, the first species to thrive in the habitat
are then replaced by others, which are replaced by others
in a predictable sequence. Eventually the composition of
species stabilizes as long as other conditions remain the
same. This more or less stable array of species is called a
climax community.
In primary succession, changes begin when pioneer spe-
cies colonize a newly available habitat, such as a recently
deglaciated region (Figure 24.3). In secondary succession,
a community develops toward the climax state after parts
of a habitat have been disturbed. For example, this pattern
occurs in abandoned fields, where wild grasses and other
plants spring up when cultivation stops. Changing climate,
natural disasters (such as forest fires), and other factors
often interfere with succession so we rarely see truly stable
climax communities.some Basic principles of ecology
F i g u r e 24.1 Examples of biomes are A the hot desert near
Tucson, Arizona, and B tropical aquatic realms such as this
coral reef in the South Pacific.BA
George H.H. Huey/Encyclopedia/Corbis24.1
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