An animal species becomes extinct① when it fails to produce enough young generation to keep pace with the death rate. We can tell from fossil② evidence in rocks that many living species have become extinct over the millions of years since life began.
If they have too far specialized nature to change when environment changes， or haveto compete with a better adapted and more powerful animal， extinction is the fate of many animals， which is a natural process. Because of remarkable technical developments during the past few centuries， man has destroyed or nearly destroyed some species by killing them or by completely changing their natural environment at such a rate， so that they couldn’t produce enough offspring③.
Plants in nature have been cut out and many species of animals will be made extinct completely because of these and similar clearances of natural vegetation. Large numbers of animals have been hunted and killed for food. The North American buffalo is a case of the species extinction because of being hunted.The number isso great that the hunters may not realize the danger of the animal’s extinction. But even when the danger is widely publicized， hunters still choose to ignore the threat to the speciesbecause of the great financial rewards for them.Attitudes like this have led to hunters killing animals for furs， for ivory or merely for ornaments④.
Many people are concerning about animals and wildlife conservation. One way to preserve species under threat of extinction is to remove them to zoos and parks and breed them there. There is always the chance that enough offspring will be born and returned to their natural environment one day， supposed that this kind of animals can be survive and certainly hunters don’t kill them again！
It is great pleasure to watch wildlife in natural or near natural environments. And tourism can add to the income for countries. In other words， animals are still resources which are in a very different form.
① extinctadj. 绝种的，灭绝的
② fossiln. 化石
③ offspring n. 子女，子孙，后代
④ ornamentn. 装饰品\[C\]；装饰，修饰\[U\]
谁来保护它们的安全
不论何种动物，当每一代不能繁殖出足够的后代，不能与其死亡数字维持基本平衡之时，这种动物就会逐渐灭绝。从岩石中的化石遗留下的证据中我们可以看出：自从地球上开始有生命时，在若干个百万年中，很多物种已经逐渐地灭绝了。
对于一种动物来说，如果它的生性过于特殊化，但是又不能随着环境的变化而改变自己，或者是当它必须与一种可以更好地适应环境、同时又更加强大的动物相竞争之时，面临灭绝就是他们的命运，这是个很自然的演化过程。随着各项科学技术的迅猛发展，人们以惊人的速度大量杀死了某些种动物，或以惊人的速度彻底改变了这些动物生存的自然环境，导致这些动物不能生育繁衍出足够的后代而使其濒临灭绝。
由于在一些地区以及和这些地区相类似的地区，自然界的植物已经被砍伐净尽，许多种动物将完全有可能灭绝。大批的动物被当作食品而遭猎杀。北美洲的野牛就是因为捕猎而接近于灭绝的物种之一。由于这些动物的数量非常庞大，以致于猎手们意识不到这些动物会有灭绝的危险。但即使是他们已经知道这种动物行将灭绝，面对偷猎的巨大回报，他们也会选择对其采取不理睬的态度，这种态度导致了猎人为了获得毛皮、获得象牙或者仅仅是为了用作装饰品就去猎杀动物。
许多人都在关心动物及野生动植物的保护工作。一种方法就是把这些物种搬进动植物园里面去，并让这些动植物在那里生息繁衍下来。假如这种动物能存活下来，并且猎手们不再杀死它们，那么等将来它们繁衍出足够的后代之后，就总会有机会让它们回到大自然的环境中去！
在大自然的怀抱中或是在接近于大自然的怀抱当中，欣赏野生动植物，真是一大赏心乐事，况且这种旅游观光业也能为国家或地方增加收入。换句话说，动物其实是另一种不同形式的资源。