托福口语 Task 4

Now let's talk about a fascinating phenomenon in animal behavior called 'biological altruism.' This occurs when an animal acts in a way that benefits another individual at a cost to itself. But why would an animal do that? The main point I want to make today is that biological altruism often evolves because it helps the animal pass on its own genes indirectly, through relatives. Let me give you two examples. First, consider the Belding's ground squirrel. When a predator like a hawk approaches, a squirrel may give a loud alarm call to warn others, even though this draws the predator's attention to itself, increasing its own risk of being caught. However, the squirrels that give the alarm are usually females who live near their mothers, sisters, and daughters. So by warning them, they protect their own genetic relatives, who share many of the same genes. Second, think of honeybees. Worker bees sting intruders to protect the hive, even though stinging causes the bee to die. But worker bees do not reproduce themselves; instead, they help their mother, the queen, produce more sisters. Since worker bees are more closely related to their sisters than they would be to their own offspring, sacrificing themselves for the hive actually increases the survival of their shared genes. So in both cases, the seemingly selfless act actually helps the animal pass on its genes indirectly.