A zoological garden, shortened to zoo, is an institution in which living animals are exhibited in captivity. In addition to their status as tourist attractions and recreational facilities, modern zoos may engage in captive breeding programs, conservation study, and educational outreach. Zoos are a subject of controversy stemming from many sources, including the quality of life of the animals they exhibit, and the perceived necessity or purpose of exhibiting captive animals at all. Zoos are frequently criticized by animal rights groups.
Collections of wild animals existed already in the ancient civilizations of Mesopotamia, Egypt, and China. In medieval Europe some monarchs, monasteries, and municipalities continued to maintain collections of wild animals. The transition from menagerie, a predominantly private collection, to public institution marks the beginning of the modern zoo concept. Collections established during the nineteenth century began calling themselves zoological gardens. Throughout the nineteenth and twentieth centuries, many new zoos and related facilities were founded for very different motives and purposes.
Zoo professionals proclaim demanding aims for their institutions, from educating the public to conservation of biodiversity. Many zoos define their aims as recreation, education, research, and conservation. Animal-rights groups claim that there is a wide gap between these claimed aims and actual practice, and that zoos have commercial and entertainment purposes in mind as well as financial profit.

Evolution of the modern zoo concept
The transition from menagerie, a predominantly private collection, to public institution marks the beginning of the modern zoo concept. Collections established during the nineteenth century began calling themselves zoological gardens. In some cases this was simply fashionable since zoos were considered professionally managed facilities, whether they were or not. In other cases there was an emphasis on education and science rather than on entertainment. The first modern zoo, established particularly for scientific and educational purposes according to its founders, was the Ménagerie du Jardin des Plantes as part of the Muséum national d'histoire naturelle in Paris (1793). It was, significantly, laid out like a picturesque park -- a semblance of Nature emphasized by Rousseau -- while the buildings themselves housed caged animals as if in museum display cabinets. About thirty years later, the members of the Zoological Society of London adopted the idea of the early Paris zoo when they established London Zoo in 1827. It opened in 1828 in Regent's Park, admitting members and their guests. Only in 1847 were working people allowed in, for a shilling. The taxonomic presentation of animals at the London Zoo became the model for the nineteenth century. The success of London Zoo set off a Victorian wave of similar establishments.
In the United States, physician William Camac initiated the incorporation of the Zoological Society of Philadelphia in 1859. According to the society's charter, "The object of this Corporation shall be the purchase and collection of living wild and other animals, for the purpose of public exhibition at some suitable place in the City of Philadelphia, for the instruction and recreation of the people." The American Civil War interrupted these efforts so that the opening of the Philadelphia Zoo delayed until 1874. Some years ago, the Central Park menagerie evolved from gifts of exotic pets and other animals informally given to the Park, beginning, apparently, with a bear and some swans deposited near New York's arsenal on the edge of Central Park in 1859. About 1861/62, a smaller zoo with lower standards had been already established in New York City, the Central Park Zoo. In 1864 it received charter confirmation from New York's assembly. When the first American zoological gardens came into existence, only a few supporters of the early animal welfare movement spoke out against zoos. Humanitarians protested cruelty in training animals for circuses more often than they opposed zoos. Their concerns were that zoo animals were healthy and well cared for, and not subjected to cruelty or pain.
Throughout the nineteenth and twentieth centuries, many new zoos and related facilities were founded for very different motives and purposes. Cultural and philosophical attitudes as well as political developments such as imperialism had an impact on the appearance and aims of zoological gardens. Human beings were sometimes displayed in zoos along with non-human animals, supposedly to illustrate the differences between people of European and non-European origin (“Human zoos”). According to historians Eric Baratay and Elisabeth Hardouin-Fugier the zoos of that period reflected the determination of imperialist nations to classify and dominate.
When ecology emerged as a matter of public interest through the 1970s, a few zoos began to consider making conservation their central role, with Gerald Durrell of Jersey Zoo, George Rabb of Brookfield Zoo, and William G. Conway of Bronx Zoo leading the discussion. Since then, zoo professionals became increasingly aware of the need to engage themselves in conservation.. The changes at zoos have served both the ideology of environmentalism and the day-to-day needs of zoos to maintain their collections. Many of contemporary zoos led by professionals show fewer species and display social animals in groups; landscape immersion exhibits replicate animal habitats.

Recreation
Recreation, which is close to entertainment and pleasure, does not benefit the welfare of the zoo animals, but that of the zoo visitors. Jamieson points out that "we should have the honesty to recognize that zoos are for us rather than for the animals". According to Swiss zoologist Heini Hediger recreation is one of the most important aims of the modern zoo in the face of proceeding urbanization and alienation from nature. People, especially from urbanized areas, should be given the opportunity to relax and to enjoy a naturalistic environment in their very neighbourhood.

Education
Since the beginning of the modern zoological gardens education and therefore the propagation of biological knowledge has been one of the most prominent aims claimed by zoo professionals. Already in 1829, London Zoo published its first guide to the zoo. Today’s educational efforts of zoos concentrate mostly on ecological and conservation issues. The idea of conservation education at zoos has a longer history than it is often acknowledged. This idea was foremost among the goals of the Arizona-Sonora Desert Museum as it was planned in the early 1950s. Animal exhibits were one component of the museum, which was begun with the goal of educating the public about the plant life and scenic value of the desert. Although the museum's focus was regional, and it was not a traditional zoo, directors of many American zoos looked to it as a model. Many zoos now have an education department, a classroom, and full time educational officers. Edinburgh Zoo has pioneered a scheme called "interlink" which combines the resources of the zoo, local museums, and the botanical gardens to create educational courses. Like several other zoos it offers teachers a range of courses from day trips with infants to intensive courses for advanced students. In 1991, over 50,000 students were involved with structured courses at Edinburgh Zoo. However, critics say that there is no educational value in exhibiting wild animals in artificial environments. According to them true respect for wildlife could only be stimulated by learning about animals in their natural habitat