Chapter 41
Self-Quiz
Unit 6: Interaction with the Environment
Growth of Populations
Review
A
is a group of individuals of the same species that live in the same geographic
location.
Populations change in size over time. Unless reproduction is checked in some way, a population will exhibit a
curve
of
growth,
but environmental limits place prevent populations from exceeding the
capacity, and they usually stabilize at a
curve,
where birth and
rates
are balanced by death and
rates.
species
often experience an initial exponential growth due to lack of
or
.
Removing an
species can also allow native species to rebound in a
recovery
curve.
Some populations undergo
cycles
of growth and decline due to
or
limits.
Excessive populations can degrade the environment and reduce its
capacity,
leading to a population
; an example is the
reindeer
on St. Matthew Island.
Habitat
fragmentation
may also have an effect on population size, often in an unpredictable fashion.
World
human
population growth is
currently
, but this pattern cannot be sustained indefinitely. Eventually, either we will place limits on ourselves that curb population
growth,
or the environment will do it for us.
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A Miserable Life on Overcrowded Earth in 2100
Chapter 42
Self-Quiz
Unit 6: Interaction with the Environment
Interactions among Organisms
Review
The focus of ecology is on interactions between
and their
, including other organisms.
Interactions between two species where both
benefit
is
called
, or
.
Examples
include bacteria that live within the cells of
aphids,
mealybugs,
and
whiteflies
and help the insects digest plant sap. In turn, these plant suckers are often
protected
by
which "milk" the
"honeydew"
secreted by the insects.
mutualism occurs when each species depends on the other for reproduction. An example is the
which actively pollinates the
Yucca plant
to ensure that its larva will have seeds to eat.
Interactions where one species benefits and another is harmed are called
interactions,
and include 2 major kinds:
and
.
Predators
usually
their prey, while
parasites
often feed upon their
without killing them. Consumers can be a strong
on victims to evolve defensive mechanisms. Examples include the
spines on
and
, and the
prickles
of
.
Competition
occurs when
both species
in an interaction share a
. Competition between
similar species
can lead to
so that each species can exploit a different resource.
Species may compete directly by preventing access to resources (
competition),
or indirectly in a race to share limited resources (
competition).
New Water Flea Invades Southern Lake Michigan
Wolves Decline, Moose Increase in Isle Royale National Park
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