Narrator: Listen to part of a lecture in a biology class.
Professor: Today we’re going to talk about a fascinating adaptation in the animal kingdom: the bombardier beetle. This small insect has evolved a unique defense mechanism. When threatened, it sprays a hot, irritating chemical spray from its abdomen. The spray is produced by mixing two chemicals, hydroquinone and hydrogen peroxide, in a special chamber. This reaction generates heat and creates a boiling, noxious substance that can reach temperatures of up to 100 degrees Celsius. The beetle can aim this spray with remarkable accuracy, rotating its abdomen to direct the stream at predators like ants or spiders. Interestingly, the spray is pulsed, not continuous, which allows the beetle to conserve chemicals and avoid overheating. Researchers have studied this mechanism for inspiration in engineering, such as developing more efficient fuel injectors. So, the bombardier beetle demonstrates how even small creatures can possess complex and efficient biological systems.
❓ Pregunta What is the main purpose of the lecture?
A. A. To explain how the bombardier beetle produces and uses its defensive spray
B. B. To compare the bombardier beetle with other insects that use chemical defenses
C. C. To discuss the evolutionary history of the bombardier beetle
D. D. To describe how engineers have replicated the beetle's spray mechanism
✅ Respuesta correcta
A. To explain how the bombardier beetle produces and uses its defensive spray
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
