This article looks back at three key moments in the history of zoos at the National Museum of Natural History, and underlines their different relation to the same educational function. Historical enquiry shows us, first, that the first zoo of the Museum had been conceived since its creation with an educational purpose, aiming at citizens in a post-revolutionary context. However, what was at stake was not environmental education properly speaking, as the zoo was rather devoted to a representation in space of the classification of species. Then, the article focuses on several elements of context which, from the beginning of the 20th century, gradually introduce environmental education into the zoos of the National Museum of Natural History, from kinds of innovative scenography that contextualize animals in landscapes, to the staging of notions derived from environmental thought ("ecosystems", "biotopes", "biodiversity"). Finally, the article shows that, in their current desire to raise awareness about "biodiversity in danger", zoos are looking for a kind of self-justification of their existence, but are still confronted to ancient paradoxes.