Supporters of zoos would argue that there are many advantages to keeping animals in captivity. One of the most important of these is that there are some endangered species are protected in the zoos. Like Giant Panda, Brown Bear and Siberian Tiger and so on. Moreover, zoos give us a close encounter with wild animals. In addition to this, zoos make an easy life for animals. For example, they don't need to run about hunting for a meal, there are no real predators in the zoos and they don’t have to worry about finding partner.
On the other hand, those who oppose zoos would argue that some large animals need plenty of space to wander around in. Such as lions and polar bears, they are also endangered species but they usually breed unsuccessfully in the zoos which because of stress. Furthermore, people visit zoos for entertainment not for education. Besides, animals lose natural instincts in the zoos. If we put them to the wildlife again, they can’t survive well independently. That is a kind of tragedy is made by human.
On balance, I feel that zoos are not suitable for all animals, it’s really depends on what species they are, what behaviour they have and where is better for them to live. However, the zoos need to do more researches for understand animals better and improve the living environment of them