1. Environmental Change and Stability
Reporting Category 5
Interdependence Within Environmental Systems
Station 18
Environmental Change and Stability

2. 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.

3. Pre-Review Question True True or False
If an ecosystem is unstable, one small change such as a natural disaster could cause many species to die.
True

4. All of these are natural events that could alter an ecosystem EXCEPT:
Pre-Review Question
All of these are natural events that could alter an ecosystem EXCEPT:
Burning of fossil fuels
Wildfires
Floods
Volcanic activity

5. Pre-Review Question
If a natural disaster destroys the producers of an ecosystem, which trophic level would be the first affected?
Primary consumers
Secondary consumers
Tertiary consumers
Quaternary consumers

6. Lab Activities
You will now go to the lab and complete the activities for today’s topics.

7. Both examples are given but you only need to do one.
1. Construct a food web based on either the desert ecosystem or the freshwater ecosystem.
Desert 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.

8. Freshwater Ecosystem

9. 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

10. 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.

11. 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.

12. Write this question and answer in your journal
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

13. 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.

14. 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

15. Post Review Question
Wetlands are very specialized ecosystems. Of the following causes of wetland loss, which do people have the least control over?
Overgrazing
Droughts
Draining and filling
Discharge of pollutants