Listen to part of a lecture in a biology class. Professor: Today we're going to talk about a fascinating example of animal adaptation: the wood frog. This small amphibian, found in North America, has an extraordinary ability to survive freezing temperatures. When winter arrives, the wood frog's body undergoes a series of changes. First, its heart stops beating, and blood flow ceases. Then, up to 65% of the water in its body turns to ice, including water in its cells and between them. However, the frog does not die. How is this possible? The key is glucose. As the temperature drops, the frog's liver converts glycogen into large amounts of glucose, which acts as a cryoprotectant. This glucose enters the cells and lowers the freezing point of the water inside them, preventing ice crystals from forming that would otherwise damage cell membranes. In spring, the frog thaws and its heart restarts. This process is so efficient that the wood frog can survive multiple freeze-thaw cycles during a single winter. Now, what might be a potential risk of this adaptation?
❓ Вопрос What is the main function of glucose in the wood frog's freezing process?
A. A) To provide energy for the frog's heart during freezing
B. B) To raise the freezing point of water in the frog's cells
C. C) To protect cells by preventing ice crystal formation
D. D) To increase the amount of ice formed between cells
✅ Правильный ответ
C) To protect cells by preventing ice crystal formation
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
