Narrator: Listen to part of a lecture in a biology class. Professor: So today we're going to talk about a fascinating adaptation in some fish species—the ability to change sex. This is called sequential hermaphroditism. Now, in many reef fish, like the clownfish, the social structure is dominated by a breeding pair. The largest individual is the female, and the next largest is the male. If the female dies, the male will actually change into a female to take her place. This ensures that reproduction can continue. On the other hand, in species like the wrasse, the opposite occurs. The largest male dominates a group of females. If that male is removed, the largest female will transform into a male. This sex change is triggered by social cues, not by age or size alone. Interestingly, the transformation involves hormonal changes and can take just a few weeks. This flexibility gives these species an evolutionary advantage in unstable environments. So, as you can see, gender in these fish isn't fixed—it's a dynamic and strategic response to their social surroundings.
❓ Pregunta According to the professor, what is a key factor that triggers sex change in sequentially hermaphroditic fish?
A. A. The age of the fish
B. B. The size of the fish only
C. C. Social cues, such as the loss of a dominant individual
D. D. Changes in water temperature
✅ Respuesta correcta
C. Social cues, such as the loss of a dominant individual
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
