托福口语 Task 4

Today we're going to talk about a fascinating concept in biology called 'biological rhythms.' These are natural cycles that living organisms follow, and they often synchronize with environmental cues. One important type is the circadian rhythm, which follows a 24-hour cycle. But what's really interesting is how animals can shift their rhythms when their environment changes. Let me give you two examples. First, consider the desert kangaroo rat. It is nocturnal to avoid the intense heat of the day. However, if its burrow becomes too hot at night due to a heatwave, it will switch to being active during the cooler early morning hours. This shift helps it conserve water and avoid overheating. Second, think about the intertidal sea anemone. It lives in tide pools and has a rhythm tied to tidal cycles, not just day and night. When the tide goes out, it closes up to avoid drying out; when the tide comes in, it opens to feed. But if a pool is isolated from the tides for a while, the anemone will gradually adjust its rhythm to the actual water availability, not the clock. So, these examples show that biological rhythms are flexible, not rigid.