Bio1152
Chapter
54
Community Ecology
A
is a collection of
of various
species
that interact.
Interspecific
for limited
results in each species occupying a unique ecological
in the community due to
competitive
.
Similar species can coexist in a community if they occupy different
by
resource
.
Competition may result in
character
, where certain characteristics exhibit more divergence between
populations of two species than between
populations of the same two species.
Predation occurs when the
kills and eats the
prey.
is an interspecific relationship where two or more species live in direct and intimate contact with one another.
Parasitism
is a relationship where the
,
benefits
by
harming
its
.
benefit both
species.
benefits
one species while the other is not affected.
The species
of a community can be quantified by two
measures:
species
and relative
.
The feeding relationships in a community make up its
structure;
its organisms often form a complex
food
.
The diversity of some
communities
may depend on one
species.
Some organisms act as
species
by causing physical changes in the environment; some can act as
of
biodiversity
in the community.
Natural communities often experience periodic
and undergo changes in diversity in a process called
ecological
.
Species richness in many communities is affected by climatic factors such as
and
, which can be measured by
evapotranspiration,
as well as
of the
ecosystem.
The diversity of isolated ecosystems can be predicted by the island
model.
Bio1152
Chapter
55
Ecosystems
An ecosystem consists of all the organisms in a
, and all the abiotic factors with which they interact.
Energy
through ecosystems, while
matter
within them.
Energy entering an ecosystem is converted to
energy by primary
, and can be quantified by
productivity.
production
can be represented in a
pyramid
of
.
In most ecosystems, this low trophic efficiency is also reflected in a
pyramid
of
.
Chemicals released by humans can become
in successive trophic levels in a process called
magnification,
becoming toxic to higher level consumers.
The chemical nutrients
between
and
reservoirs
of ecosystems
The
cycle
is driven by solar energy on a global scale.
The
cycle
reflects the reciprocal processes of
and cellular
.
The
cycle
involves local cycles between organisms and soil or water.
The
cycle
is relatively localized.
Excess
fertilizer
added to the soil can runoff into streams, and together with
discharge, can lead to
, excessive algal
growth
in aquatic ecosystems.
Burning fossil fuels releases excess levels of
carbon
into the atmosphere, which is associated with global
due to the
effect.
Combustion of fossil fuels also releases excess
into the atmosphere, causing
precipitation.
The release of
(
CFCs
) has resulted in
depletion.