托福口语 Task 3

In biology, organisms often develop traits that seem to reduce their own fitness but actually benefit the survival of their group. This is called “altruistic behavior.” Altruistic behavior is defined as an action that increases the reproductive success of others at a cost to the individual’s own chances of survival or reproduction. Such behaviors are puzzling from an evolutionary standpoint because they appear to contradict the principle of natural selection, which favors traits that maximize an individual’s own survival. However, altruistic behavior can evolve if it helps close relatives who share many of the same genes, thereby indirectly passing on the individual’s genetic material.

Professor: Let me give you a classic example of altruistic behavior in ground squirrels. When a predator, like a hawk, approaches, one squirrel will give a warning call. This call alerts other squirrels to hide, but it also draws the predator’s attention to the caller, making it more likely to be attacked. Now, why would a squirrel do that? It turns out that ground squirrels live in colonies with close relatives—mothers, sisters, and offspring. By risking its own life, the calling squirrel helps its relatives escape. Those relatives carry many of the same genes as the caller, so even if the caller dies, its genes are more likely to survive through its relatives. In fact, studies show that calling is most common when the squirrel’s nearby kin are present, and less common when it is surrounded by unrelated squirrels.