Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about a fascinating example of ecological restoration: the reintroduction of gray wolves to Yellowstone National Park in the mid-1990s. After being absent for about 70 years, wolves were brought back to control the overpopulated elk herds. But the effects went far beyond that. With fewer elk, the vegetation, especially willow and aspen trees, began to recover along riverbanks. This, in turn, attracted beavers, which built dams that created wetlands. The presence of wolves also altered the behavior of elk, causing them to avoid open areas, which allowed those plants to thrive further. Scientists call this a 'trophic cascade'—a chain of effects that starts at the top of the food chain and ripples down to the entire ecosystem. Interestingly, the wolves even affected the physical geography, as the stabilized riverbanks reduced erosion. So, what started as a simple predator introduction turned into a powerful lesson about the interconnectedness of nature.
❓ Вопрос What is the main point the professor makes about the reintroduction of wolves to Yellowstone?
A. A. It only succeeded in reducing the elk population.
B. B. It triggered a series of ecological changes that improved the entire ecosystem.
C. C. It had negative effects on the beaver population.
D. D. It was a controversial policy that failed to meet its goals.
✅ Правильный ответ
B. It triggered a series of ecological changes that improved the entire ecosystem.
TOEFL Listening Tips
Skim the questions first to predict the content
Watch for signal words in lectures and conversations (however, actually, in fact)
For main idea questions, focus on the beginning; for detail questions, focus on examples and data
For attitude questions, pay attention to the speaker's tone and word choice
Take notes on keywords; don't try to write down every word
