In the past, a zoo was often a place where animals, including primates which are closely related to us, lived on concrete floors in overheated buildings and stared out, accusingly, through the bars.
For most visitors, animals were strange furry things which made you laugh and made the news by having cuddly babies. Brumas, London Zoo's baby polar bear, was national news for weeks after his birth in 1949. Toy models of him are now collectors' items.
Since then have come people such as Molly Badham, who started Twycross Zoo in 1963 with Natalie Evans. They expanded out of their pet shop in Sutton Coldfield to the point where their zoo now has the largest collection of primates in the country.
"We never dreamed we'd end up so large," she says. "What started as a hobby is now of great value to the survival of primates. There are few places in the world where they are safe now."
Once, zoos were having to justify their existence against doubts about the morality of captivity but their conservation role is now established. Twycross is one of a world-wide group of zoos co-operating to look after bonobos, a chimpanzee-like creature not recognised as a species until the 1930s. There are only about 15,000 in the wild, all living in an area of Zaire where the habitat is under pressure from forest depletion, hunting and warfare.
In some cases, such as the Siberian tiger and Mongolian wild horse, there are now more examples in zoos tan in the wild. An estimated 6,000 species of land vertebrates need captive breeding if they are not to become extinct this century.
The public now receives constant messages from the media about dangers to the environment and the true nature and habits of wild creatures. Chimps' tea parties, once popular at Twycross, have long since vanished.
"The chimps actually had a whale of a time but attitudes change and, where once people came in for a laugh, they now take animals seriously," said Molly.
The UK Federation of Zoos sets out detailed guidelines for zoo education departments. Eighty per cent of zoos have education officers and education centres. "Zoo education is expanding all the time," said Simon Garrett, education officer at Bristol Zoo, and chair of the federation's education committee. "We've built a new education centre here at Bristol because we couldn't fit everything in."
Stephen Woollard, his assistant, added: "We try to respond to what teachers want. So if, for example, a teacher rings up and says 'we're doing Christopher Columbus', we'll think, 'right there were rats on the ships, and we've got some of those. They landed in central America so let's look at some rain forest animals'. Then we'll go on to what's happened to the rain forest since Columbus was there. It's about being open and adaptable."
The ultimate aim, he said, is to get teachers thinking of the zoo as the first resource for much of their work.
UK Federation of Zoos, Zoological Gardens, Regent's Park, London NW1 4RY. Tel: 0207 586 0230;e-mail: email@example.comTwycross Zoo, Twycross, near Atherstone, Warwickshire CV9 3PX.www.twycrosszoo.com