托福口语 Task 4

Today we're going to talk about a fascinating concept in animal behavior called 'biological altruism.' This is when an animal acts in a way that benefits another individual at a cost to itself. The main point I want you to understand is that such seemingly selfless acts often have a hidden evolutionary logic—they help ensure the survival of the altruist's own genes, either directly or indirectly. Let me give you two examples. First, consider the meerkat. When a meerkat sentinel spots a predator, it gives a loud alarm call and then dives into its burrow. This warning puts the sentinel at greater risk because it draws the predator's attention to itself. However, the sentinel is often closely related to the other meerkats in the group, so by saving them, it increases the chance that its own genetic material, shared with relatives, will be passed on. Second, look at vampire bats. After a successful blood meal, a bat will sometimes regurgitate blood to feed a hungry, unrelated roost-mate. This seems purely generous, but if that bat later fails to find food, the recipient is likely to return the favor. So the act ensures a long-term mutual benefit, which indirectly helps the bat survive and reproduce over time.