Difference between wildlife sanctuaries,Biosphere reserves,National Park,Zoo

Biosphere reserve is natural forest and a nartional park is a place where animals are kept behind iron bars.An wildlife sanctuary is a facility where animals are brought to live and be protected for the rest of their lives.A sanctuary is not open to the public in the sense of a zoo; that is, the public is not allowed unescorted access to any part of the facility.What distinguishes a sanctuary from other institutions is the philosophy that the residents come first ,whereas sanctuaries act on behalf of the animals, and the caregivers work under the notion that all animals in the sanctuary, human and non-human, are of equal importance.