听力原文： All warm-blooded animals are very helpless at first. Young birds and young bats must be taught to fly. Thousands of young seals drown every year. They never learn to swim 'naturally.' The mother has to take them out under her flipper and show them how. Birds sing without instruction however, they do not sing well unless they are able to hear older members of their species. Older harvest mice build better nests than beginners. Frank Buck says that the young elephant does not seem to know at first what his trunk is for. It gets in his way and seems more of a hindrance than a help until his parents show him what to do with it. Insects, seem to start life equipped with all necessary reflexes, but they seem to improve their talents with practice. Young spiders, for example, begin by making quite primitive little webs. They attain perfection in their art only after much time. Older spiders, if deprived of their spinnerets, will take to hunting. (33)