การฟัง TOEFL

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Listen to part of a lecture in a biology class. The professor is discussing animal communication. Professor: Today, we're going to talk about a fascinating aspect of animal behavior: communication. While many animals use vocal sounds, some rely heavily on visual signals. For example, the peacock's elaborate tail is a classic visual display used to attract mates. But visual signals have a drawback—they require light and a clear line of sight. In dense forests or murky waters, visual signals are less effective. That's where chemical signals come in. Many insects, like ants and moths, release pheromones—chemical substances that can travel long distances and persist in the environment. These chemicals can convey messages about food sources, danger, or reproductive readiness. Interestingly, some animals combine multiple modes. Take the honeybee, for instance. Its famous waggle dance is visual, but it also produces vibrational signals that travel through the honeycomb. This multimodal approach ensures the message gets through even if one channel fails. So, the key takeaway is that evolution has shaped communication to be as efficient as possible in specific habitats.