Yeah,I agree with you @chetanpadliya. But,not completely.
More than 100 species of animals become extinct in the wild every day. Humans destroy their habitats, or hunt them down to the last specimen.
Keeping wild animals was long a privilege of the nobility – 4,000 years ago, the emperor of the Xia dynasty in China had menageries. Later, Assyrian rulers collected crocodiles, and the Aztecs had giant birds of prey. The Medici princes of Italy appreciated exotic animals in their parks, as did Louis XIV of France and especially the Habsburg king, Franz I. Stephan, who, in 1752, founded what is now the oldest existing zoo in the world, the Schönbrunn Zoo in Vienna.

But royals were not concerned with protecting endangered species. Today, this is one of the major concerns of modern zoos in the 21st Century. For many species habitats are disappearing. More than seven billion people must be supplied with food and raw materials, and farms and mines devour land all over the world. Then, there is the energy crop production, which devours acres upon acres of land, turning it into fields, orchards, plantations, building sites. When the habitats disappear, so do the animals.

The diversity of extinctions

Habitat destruction is the main reason for the extinction of species. Climate change will continue to claim victims, especially for cold-adapted species. Humans also kill animals directly. Gorillas are killed by marauding gangs in the blood diamond trade, and rare animals end up as bush meat in African and Asian markets. At night, when African weaver birds are gathered together to sleep, their roosting trees are burned by farmers who see them as pests. Poaching of elephants has also increased dramatically in West Africa. And due to the lust for aphrodisiacs, the only chance many rhinos have to survive is if they are accompanied by armed guards.

In brief, the options are dismal. So, are zoos the last resort for keeping animals out of harm's way? Or are the critics right: keeping animals in captivity is animal cruelty?. The animal rights group Peta has called on Germany's Agriculture Minister, Ilse Aigner, to ban big cats in zoos. "If a tiger has the opportunity to attack a person, or to escape, it will use it," says Peta employee Peter Höffken. Cheetahs and chimpanzees that escape repeatedly from enclosures prove that they want to get out. To Höffken, zoos are "high security prisons."
Success stories in conservation:
Manfred Niekisch is convinced that zoo animals are still wild animals. "A wild animal will always be a wild animal, even though it lives in a zoo,” he said. Niekisch, the director of the Frankfurt Zoo, believes that the animals at the zoo are not simply mentally broken. Behavioral disorders that develop from having bored cheetahs in cramped cages would not happen in a modern well-managed zoo.

Whether turtle or tiger, there are now sophisticated programs to make up for the disadvantages of living in spatial confinement, Niekisch ensured. "Most importantly, because of advances in veterinary medicine, we can now treat animals much more humanely. For example, apes once lived, for hygiene reasons, in enclosures with bathroom architecture like tiles and steel. But today they live on soft ground in artificial forests, and are thus much closer to nature."
Because their quality of life is so high, zoo animals often live to be much older than in the wild and many species willingly breed. There are now large zoo populations – two thirds of all Siberian tigers live in zoos. The species are preserved, and some day, if conditions are right, these animals could be reintroduced into the wild to establish new populations. "This idea works - just look at the success stories of the European bison, the Przewalski horse, or the California condor," said Manfred Niekisch. Even today's stocks of scimitar oryx and screwhorn antilopes in North Africa, the golden lion tamarin in South America or the bearded vulture in central and southern Europe would not exist without the reintroduction from zoos.

"Today, zoos are for saving irreplaceable biodiversity!” says Dag Encke, head of the Nuremberg Zoo. "No other facility has more knowledge than a zoo to create a vibrant, viable population."
Finally I want to say one thing that @chetanpadliya zoo is not always a prison to animals,It might be it's world(it my look artificial for us,but it might be a real world for it).
I appreciate your concern about animals.Thanks for the reply @chetanpadliya