Edward O. Wilson, the “modern-day Charles Darwin”, damaged his right eye when he     1    (catch) a fish in the river near his home at seven. The poor eyesight only allowed him to observe small     2    (creature), like ants. Interested in the selflessness of ants, which would sacrifice     3    (them) for their colony (群体), Wilson developed a theory, confirming the existence of altruistic (利他的) behavior in a wide range of species. It made him influential as both a close observer and a pioneering theorist.

If a sixth mass extinction occurs, scientists who have studied the issue believe that up to three quarters of all species on Earth could die out. Of course, as we humans depend on so many species for our survival, we would also be at risk of     1    (die)out. Our world and our lives depend on the balance in nature     2     animals and plants. Without forests, we would have no air, and without clean water we would be unable     3    (survive).