According to the website Biology Online, a habitat is a "place where an organism or a biological population normally lives or occurs." More broadly, a habitat is a "place being occupied by an organism, population, or community," which can include creatures that do not normally occur in the area but were brought there and now live there.
Some animals are endemic to one area, meaning they only have one natural habitat in the world and do not live anywhere else. Giant pandas, which live only in the bamboo forests of China, are an example of an endemic. By contrast, some animals can be found all over the world, even if the separate populations evolve into their own subspecies. The lion is an example of this, as its natural habitat is in Africa as well as a part of India. Rats, which spread across the world with humans, have an extremely wide natural habitat.
A natural habitat can also refer to a specific area in the environment in which an organism lives. This is exemplified by viruses, bacteria and parasites: The human body is one of natural habitats of certain strains of beneficial bacteria, but some are only found in our intestines, while others live only in the mouth and throat.
A natural habitat may also refer to the human population. According to Dictionary.com, habitat also means "the place where a person or thing is usually found" or "a special environment for living in over an extended period, as an underwater research vessel." Therefore, New York may be the home of many artists and writers, as the city's support for the arts breeds new ideas, while a submarine can become a temporary, but non-natural habitat for scientists.
Some animals, like humans, have evolved to live outside the natural habitat where they began—Africa, in the case of humans—so much so that now the entire world, with the exception of a few extreme regions, can be considered the natural habitat of people, given that self-perpetuating colonies of people live on every continent but Antarctica.
Other animals, however, cannot adapt or live outside their natural habitat, so when humans destroy this habitat with such activities as logging in the Amazon Rainforest or draining swampland to build houses, many animals can live nowhere else and become extinct.