L3
讲座
1. What is the lecture mainly about?
Why the gray wolf disappeared from Yellowstone National Park in the 1920s
Why Yellowstone National Park has become a popular tourist destination
How certain animals and plants affect the ecology of Yellowstone National Park
How an increase in the beaver population in Yellowstone National Park has altered its ecosystem
2. What is an assumption of the top-down trophic cascade hypothesis?
That a predator is the most important influence within an ecosystem
That a meat-eating predator will usually seek out an environment containing multiple herbivores
That a food chain with more than one predator is essentially unstable
That the number of herbivores in an environment will determine what types of plants grow there
3. What is the professor’s opinion about an agreement between Canada and the United States in the 1990s?
It took too long to implement.
It was an effective way to strengthen the relations between two countries.
It should not have been attempted at a time when public disapproval was so strong.
It provided an opportunity for research that is quite rar.
4. What does the professor say happened after wolves returned to Yellowstone National Park?（多选题）
Owners of nearby cattle ranches protested.
The elk population decreased.
Wolves did not reproduce as quickly as expected
Willow shrub numbers remained very low.
5. Why does the professor mention Kristin Marshall’s study?
To emphasize its failure to account for the role played by certain species
To compare it with a similar study conducted in the 1990s
To highlight the way that beavers help willows grow
To explain why elk prefer to feed on willows
6. What is the professor’s opinion about top-down trophic cascade in relation Yellowstone National Park?
It provides the best explanation for why the wolves there disappeared.
It ignores certain factors that affect the ecological balance of the park.
It has less predictive power than a bottom-up approach.
It was never intended to be used to describe such an environment.
