การฟัง TOEFL

🎧 บทถอดเสียง

Listen to part of a lecture in a biology class. The professor is discussing animal communication. Professor: So we've talked about visual and auditory signals in animals. But today, let's consider chemical communication, specifically pheromones. Now, pheromones are chemicals released by an animal that affect the behavior or physiology of others of the same species. For example, in many insects, females release sex pheromones to attract males over long distances. This is highly efficient because chemical signals can travel in air or water and persist for a while, even when the sender is no longer present. However, in vertebrates, the role of pheromones is more complex. Take mammals, for instance. They often use scent marks, like urine or gland secretions, to signal territory boundaries or reproductive status. But here's an interesting twist: some scientists argue that certain chemicals we call pheromones in mammals actually function more as odor cues, because they require learning and context. So, the distinction between pheromones and other chemical signals isn't always clear-cut. Now, let's look at a classic example: the honeybee. The queen bee produces a pheromone that suppresses the development of ovaries in worker bees, maintaining social hierarchy. This shows how a single chemical can regulate a whole colony. Any questions so far?