Download Station 18

Reporting Category 5
Interdependence Within
Environmental Systems
Station 18
Environmental Change and Stability
Essential Question – Bell Ringer
How is the stability of an ecosystem
affected by a hurricane?
High winds and flooding can destroy
habitats and living organisms, and
saltwater may flood land and kill
vegetation.
Pre-Review Question
True or False
If an ecosystem is unstable, one small
change such as a natural disaster could
cause many species to die.
True
Pre-Review Question
All of these are natural events that could
alter an ecosystem EXCEPT:
a.Burning of fossil fuels
b.Wildfires
c.Floods
d.Volcanic activity
Pre-Review Question
If a natural disaster destroys the producers
of an ecosystem, which trophic level would
be the first affected?
a.Primary consumers
b.Secondary consumers
c.Tertiary consumers
d.Quaternary consumers
Lab Activities
• You will now go to the lab and complete
the activities for today’s topics.
1. Construct a
food web based
on either the
desert
ecosystem or
the freshwater
ecosystem.
Record your web in
your journal with
the names of the
organisms. You do
not need to draw
the organisms.
Both examples are
given but you only
need to do one.
Desert Ecosystem
Freshwater
Ecosystem
Discuss with your partner:
How can the roadrunner (desert) or alligator
(freshwater) occupy two different consumer
levels in the food web?
Both the roadrunner and the alligator can occupy tertiary
and quaternary consumer levels depending on which
food chain within the food web is examined.
For example, the alligator in one food chain preys on
secondary consumers and therefore occupies a tertiary
consumer level. In a different food chain, however, the
alligator preys on tertiary consumers and occupies the
quaternary consumer level
Discuss with your partner:
How would the stability of the ecosystem be
affected if the producers in your food web
were destroyed by a natural disaster ?
• If a natural disaster destroys the producers in an
ecosystem, the primary consumers are affected first
since their food source has been limited. The primary
consumers decrease in numbers or die if they cannot
migrate to new feeding grounds. This causes greater
competition among the secondary consumers that
depend on the primary consumers for their food.
Competition continues through the tertiary and
quaternary consumer levels until the ecosystem begins
to stabilize with the return of producers.
Discuss with your partner:
How would the stability of the ecosystem be
affected if the primary and secondary
consumers were destroyed by the disaster ?
• When primary and secondary consumers are destroyed
in an ecosystem, the producers do not have organisms
that feed on them, and they overgrow. With much of their
prey gone, the tertiary consumers experience increased
competition, which reduces their numbers. The reduction
in the number of tertiary organisms affects the
quaternary consumers, reducing their numbers as well.
Only when there is a return of primary and secondary
consumers will the ecosystem regain stability.
Write this question and answer in your
journal.
If the quaternary consumer is eliminated from
the food web, what affect would its absence
have on the stability of the ecosystem?
• If the quaternary consumer is eliminated from
the food web, the tertiary consumers will
increase in number, which means they would
feed more heavily on the secondary consumers,
reducing their numbers. The decrease in
secondary consumers would then cause an
increase in the primary consumers, which in turn
would lead to overconsumption of producers
I need to remember………
• Mutualism, commensalism, parasitism, and
predator/prey relationships are all types of
interactions that occur among organisms in an
ecosystem.
• The stability of an ecosystem can be affected by a
natural disaster.
• Natural disasters such as hurricanes, droughts,
floods, and so on can alter the stability of an
ecosystem. These disasters can cause some
organisms to diminish in number or become extinct so
that their niche in an ecosystem is altered. It can take
years for an ecosystem to recover from a natural
disaster and regain stability.
Post Review Question
Bison feed on grass in a prairie ecosystem. Wolves
prey on the bison. How would a drought affect the
carrying capacity of the bison in this ecosystem?
A. Increase, because fewer wolves would prey on
bison
B. Decrease, because more wolves would prey on
bison
C. Increase, because bison would have more
available food
D. Decrease, because fewer plants would be
available as food
Post Review Question
Wetlands are very specialized ecosystems.
Of the following causes of wetland loss,
which do people have the least control over?
a.Overgrazing
b.Droughts
c.Draining and filling
d.Discharge of pollutants