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Ecosystems
Response to
Stress
Ecosystems,
communities, and
populations are in a
constant state of
change in response to
natural and
anthropogenic stress.
Homeostasis (stability)
Maintenance
of
favorable internal
conditions despite
changes in external
conditions.
3 aspects of stabililty
Inertia-
persistence.
The ability of a
population or
ecosystem to resist
change.
Constancy-
ability of
a population or
ecosystem to
maintain a certain
size or stay within
certain limits.
Resilience-
ability of
a population or
ecosystem to bounce
back once change has
occurred.
Population Dynamicspopulations change in
size, density, dispersion
and age distribution in
response to changing
conditions. Ex. Alligators
after Ike
Biotic Potential
Max
rate that a
population can
increase with no
limits on growth.
Exponential growth.
Environmental Resistance
All
the factors acting
jointly to limit
population growth.
Logistic growth.
Carrying Capacity
Number
of individuals
that can be supported
by an ecosystem over
time. Determined by
environmental
resistance.
Limiting Factors
The
factor in
environmental
resistance that limits
the population
growth.
Density Dependent L.F.
Factors
which
become more
influential as
population size
increases.
Density Independent L.F.
Factors
which are not
influenced by
population size.
Population Curves
Stable
(Kstrategists). A species
whose population
fluctuates slightly
from its carrying
capacity.
Irruptive-
a species
population fluctuates
because of periodic
unforeseen factors
like food increases,
good weather, or
fewer predators.
Cyclic
(r-strategists)a species which
undergoes sharp
population increases
followed by sudden
drops. Boom/bust
curve.
Ecological Succession
The
replacement of
one community by
another in response
to change in an
ecosystem.
Primary Succession
Occurs
in a place
where organisms
have not previously
existed.
Ex. Volcanic islands.
Primary Succession
Pond Succession
Secondary Succession
Occurs
in a place
where a community
has previously
existed.
Ex. Burned forest,
abandoned farms.
Secondary Succession
Pioneer Communities
First
organism to
inhabit an ecosystem.
Ex. Lichens, mosses,
grasses, insects,
rodents.
Climax Communities
The
final organisms
to inhabit an area.
These will not be
replaced until a major
change occurs.
Ex. Forest, Deer,
Wolves