Help is at hand and what is even better - visual help. If you are asked what biodiversity is, you can simply point your interrogator to this very cool explanation. The animated short film was made by students of the Vancouver Film School.
The students involved in the project were Amanda Healey, Jesse Lang, Juan Carlos Arenas and Robert Ramalho and they created it through the VFS Digital Design program. Congratulations to all of them - this animation should be sent out to schools immediately! What about a text based explanation, however?
Wikipedia defines biodiversity like this:
Biodiversity is the variation of life forms within a given ecosystem, biome, or on the entire Earth. Biodiversity is often used as a measure of the health of biological systems. The biodiversity found on Earth today consists of many millions of distinct biological species. The year 2010 has been declared as the International Year of Biodiversity.
It certainly makes sense, but which explanation do you prefer?
Yup. File under better explanation than Wikipedia.