Biodiversity, n. 
The variability among living organisms on the earth, including the variability within and between species and within and between ecosystems.

Biodiversity, (biological diversity), is the variation of life at all levels of biological organization, referring not only to the sum total of life forms across an area, but also to the range of differences between those forms. Biodiversity ranges from the genetic diversity in a single population to the variety of ecosystems across the globe.

Greater biodiversity in ecosystems, species and individuals leads to greater stability.