托福口语 Task 4

Today, we're going to talk about a fascinating concept in animal behavior: biological clocks. These are internal mechanisms that regulate an organism's daily rhythms, from sleep-wake cycles to feeding patterns. They are not just a response to external cues like sunlight, but are actually driven by internal genes. Let me give you two examples to illustrate this. First, consider the common fruit fly. Researchers found that a specific gene, called 'period', controls the fly's daily activity rhythm. When this gene is mutated, the fly's sleep-wake cycle becomes completely irregular, even when exposed to constant light or darkness. This shows that the internal clock is genetically programmed. Second, take the example of humans who work night shifts. Their external environment changes, but their internal biological clock still tries to maintain a normal daytime rhythm, leading to feelings of fatigue and disorientation. This demonstrates that our biological clock is not easily reset by external factors. So, the main point is that biological clocks are intrinsic, genetically driven systems that strongly influence behavior, regardless of environmental conditions.