การฟัง TOEFL

🎧 บทถอดเสียง

Narrator: Listen to part of a lecture in a biology class. Professor: Today we're going to talk about mimicry, specifically Batesian mimicry. This is a phenomenon where a harmless species evolves to resemble a harmful or distasteful species to avoid predators. A classic example is the scarlet king snake, which mimics the venomous coral snake. The coral snake has red, yellow, and black bands, with the red and yellow touching. The king snake has similar colors, but the red and black touch. Predators learn to avoid the coral snake's bright warning colors, and they also avoid the king snake, even though it's harmless. However, mimicry isn't always perfect. Some mimics only resemble the model in general color patterns, not exact details. This suggests that predators might not be very discerning, or that the mimic gains enough protection without perfect imitation. Recent studies show that imperfect mimics are actually more common than perfect ones. Why? One theory is that predators avoid any pattern that vaguely resembles a dangerous animal, so perfect mimicry isn't necessary. Another idea is that perfect mimics might be too costly to evolve if the predator's learning is not very precise. So, in nature, evolution favors 'good enough' mimicry, not perfection.