Some paleotologists debate whether the diversity of animal species has  increased since the Cambrian period, or whether imperfections in the fossil reord only suggest greater diversity today, while in actually,there has been either stasis or decreased diversity.
the phenomena that many species have been extinction is the result of natural selection and overexploitatin to nature, there is no doubt that there are the large number of the social ungernt and pressing problems needed to be sovled, however, the protection of endangered species is our unavoidable responsibity.
The phenomenon of species extinction has become a controvertial and contentious problem since people began to focus on this problem. there are two reasons to explain the extinction of species, the first is that natural selection, the other is overexploitation that human been destroyed the habitat of wild animals. 

 

It seems to be true that there are many social urgent problems on which need us to place emphasis, because we must pay attention on these problems,and expenditure of government is limited, we donot have sufficient money to invest to protect the diversity of extinciton species,1. there are millions of people that are homeless and in hunger in our world, we do not lose sight of this serious social problems, so it is necessary and reasonable to invest the espenditure of government to solve this urgent problem.And there also are some other problems ,such as  energy crisis and financial crisis.  we could invest money on research the alternative fuels, including wind energy, solar energy, turbine energy, biological energy and so on, all of these have some flaw if we want to utilize these energy efficiently,so it is also desirable to invest money on developing the alternative energys.

 

However, human  beens   responsible to protect the endangered animal and other speices. from the moral and long time interest  perspective, human beens have the accoutability to protect the endangered animals, our offspring could not see these endergered wild animals.  they merely could visit museum and some other indirect mothods to know about these extinction species
 
the protection of the diversity of speices are benefial to human beens although there are a lare number of difficulies to overcome and confront.

firstly, these endergered animal is just oneof the members of nature, if we could not prevent the procession of extinction of species, the food chain of ecosystem could become unbalanced and even be destroyed. Another reasons is that we could make use of genome of endergered  animal in ecosystem, the genome of these species is very rare and precious ,some scientist come up with utilize these genes.
 
To sum up,we do not lose sight of invest money on solving  the urgent and pressing social problems, such as  starvation and financial crisis and so on, at the same time, we do not lose sight of invest money on protect the endergered wild animals. although there are lots of difficulties to overcome.  Nomatter how the endergered animal could become extinction, we also have the responsibility to prevent thess endergered animal from extinction.