托福听力

🎧 听力原文

Listen to part of a lecture in a biology class. The professor is discussing the behavior of ants. Professor: Today we're going to talk about ant colonies and their communication systems. You might think that ants are simple creatures, but their social structure is remarkably complex. One key aspect is how they use chemical signals, known as pheromones, to coordinate activities. For example, when a foraging ant finds food, it returns to the nest, leaving a trail of pheromones. Other ants follow this trail to the food source. However, the trail isn't permanent. If the food runs out, the ants stop using the trail, and the pheromone evaporates. This prevents the colony from wasting energy on a non-existent food source. Another interesting behavior is the use of alarm pheromones, which are released when an ant senses danger. These chemicals can trigger a defensive response in nearby ants, causing them to attack or flee. Interestingly, the intensity of the response often depends on the concentration of the pheromone. Higher concentrations might lead to a more aggressive reaction, while lower concentrations might just make the ants more alert. So, as you can see, pheromones play a vital role in the survival and efficiency of ant colonies.