托福口语 Task 4

Today, we're going to talk about a fascinating concept in biology called 'mimicry.' Mimicry occurs when one species evolves to resemble another species, often to gain a survival advantage. The main point I want to emphasize is that mimicry is not just about looking alike; it's about the specific benefits that arise from that resemblance. Let me give you two examples. First, consider the monarch butterfly. Monarchs are toxic to birds because they eat milkweed, which contains a poisonous chemical. Birds learn to avoid them. Now, there's another butterfly, the viceroy, which is not toxic at all. But the viceroy has evolved to look almost identical to the monarch. Because birds mistake viceroys for monarchs, they leave them alone, which dramatically increases the viceroy's survival. This is called Batesian mimicry, where a harmless species mimics a harmful one. Second, think about the cleaner wrasse, a small fish that removes parasites from larger fish. Larger fish recognize the cleaner by its distinctive stripes and don't eat it. Now, there's a predatory fish called the saber-toothed blenny that mimics the cleaner wrasse's appearance. When a larger fish approaches expecting to be cleaned, the blenny instead takes a bite out of the larger fish. This is aggressive mimicry, where a predator mimics a harmless species to deceive its prey. So, in both cases, mimicry provides a clear survival advantage, but the mechanism and the benefit are quite different.