As human beings have more and more effects on the environment and nature, the extinction of many species nowadays are the direct result of human process. Thus, I insist that we human beings have responsibility to maitain ecological balance and protect some endangered animals, meanwhile we also must call for a balance between the protection and the development of human itself.

First and foremost, numerous animails and plants are useful and benificial for humans. According to the statistical result of a recent survey conducted by Chinese Medicine department, over 40% of everyday medicine for Chinese people come from various animals and plants especially endangered species. The result indicate without animals and plants, many of illness cannot be treated. Furthermore, animals and plants can also provide some industrial raw meterials such as oil and fat and food resourses. Additionally, some particular animals and plants serve academic research and enlightenment for innovations. For example, some sciectists study primates for inquiry of the origin of humans and animal intelligence. And nature's energy efficiency often outsrips human technology: despite the intensity of the light firelights produce, the amount of heat is negligible. Enlightened by this, only recently have humans developed chemical light-producing systems whose efficiency is similar to the firefly's. Therefore, since they are benificial to us, we should pretect these animals and plants from extinction.
Secondly, the extinction of some species may cause unpredictable disasters. First of all, it will inevitably influence and damage food chains thus the stability of ecosystem. Every species cannot be substituted thus play a critical role in maintaining ecosystem balance. For instance, a kind of plant's extinction will lead to other 30 kinds of species to die out according to the research conducted by US Fish and Wildlife. Besides, since the nature is an extremely complicated and gigantic system, it is possible that a speices's dying out can casue unpredictable natural disasters such as flood and typhoon. As a result, we should take measures to protect species avoiding such catastrophes.
However, it is unnecessary to to save every endangered species in spite of the huge costs. According to a well-known scientists Darwin, the writer of the origin of species, many species get endangered because they are not as competitive as others and fail to survive which is known as natural selection. Consequently, some extinction of some species is not the result of human activities. Moreover, owing to the limitation of human's ability, it is impossible for us to save every species. If we do spare no effort to save every endangered species, we human race may one day become extinct as a result. Therefore, we should guarantee our survival and regular development as the foundation to protect other species.
From the analysis made above, I strongly commit to the notion that we need to call for a balance between the protection of other speices and the development of human itself.