托福口语 Task 4

Today we're going to talk about a fascinating concept in animal behavior known as 'biological altruism'—where an animal acts in a way that benefits another individual at a cost to itself. Now, this might seem to contradict natural selection, but biologists have found that such behavior can actually increase the survival of the animal's own genes. Let me give you two examples. First, consider the Belding's ground squirrel. When a predator like a hawk approaches, one squirrel will give a high-pitched alarm call to warn others. This call draws the predator's attention to the caller, making it more likely to be attacked. But the squirrel does this to protect its relatives—its siblings, offspring, and cousins—who share many of its genes. By sacrificing itself, it ensures those shared genes survive. Second, think about vampire bats. After a successful blood meal, a bat will often regurgitate blood to feed a hungry roostmate that failed to find food. This costs the donor energy and time, but the recipient is often a close relative or a bat that has previously helped the donor. So, through these acts, the helper indirectly promotes its own genetic legacy.