72.A 73.B 74.C 75.A
72.解析：根据第一段最后一句“...must make decisions－a matter of life or death”可知如果选择错了就会死掉。
73.解析：这是一道细节题。根据“...animals live in ever changing environments...it is not surprising to find that very few species indeed depend wholly upon genetic learning”这句可知多数动物都生活在一直变化的环境中，所以很少有生物完全依赖遗传性的学习。
74.解析：因为遗传性学习的作用依赖于环境变化程度，所以环境变化小，那遗传性学习作用就大。
75.解析：这是一道推断题。根据最后一段“...are a compound of individual experience added to the action patterns animals are born with.That is why animals can survive.”可知物种的生存依赖于本能和生存经验。