Keeping animals in zoos

This is a delicate issue because, on the one hand ,I am going to write an essay about the convenient ways of keeping some animals in zoos  ; and , on the other hand, it is sad to to see theses animals in zoos , instead of living in their natural habitats/enviroments , without the freedom they should have .There are many well known/important essays written on this . 

. The zoos can be visited by people to know animals from different parts of the world. In the zoos, scientists can observe and study the behaviors of the animals. The other reason is that there are some species that are  in danger of extinctions and are needed to be cared for in zoos.