Narrator: Listen to part of a lecture in a biology class. Professor: Today we're going to talk about mimicry, specifically how certain harmless species have evolved to imitate dangerous ones. This is called Batesian mimicry. For example, the scarlet king snake, which is harmless, has red, yellow, and black bands very similar to the venomous coral snake. Predators that have learned to avoid the coral snake also avoid the king snake. But here's an interesting twist: for mimicry to work, the mimic must be less common than the model. If the mimic becomes too abundant, predators might start to realize that not all snakes with those colors are dangerous, and the protection breaks down. Also, the mimic doesn't have to copy every detail perfectly; just enough to fool the predator at a glance. This raises a question: why don't mimics become perfect copies? One reason is that predators use multiple cues, like size or behavior. And also, the mimic may face trade-offs, like needing to blend into its own environment for hunting. So natural selection favors a balance, not perfection.
❓ 質問 According to the professor, what is one condition necessary for Batesian mimicry to be effective?
A. The mimic species must be more numerous than the model species.
B. The mimic species must be less common than the model species.
C. The mimic must copy every detail of the model's appearance.
D. The predator must have no prior experience with the model.
✅ 正解
The mimic species must be less common than the model species.
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