What is biodiversity?

Biodiversity refers to the variety of life in a particular habitat or ecosystem. This encompasses not only the number of different species present but also the different genetic variations within those species and the various ecosystems they form. Biodiversity is essential for ecosystem health, as it contributes to resilience, productivity, and the ability to adapt to changes in the environment. It plays a critical role in ecosystem services, such as pollination, nutrient cycling, and habitat provision, which are vital for all living organisms, including humans.

The other options you considered relate to aspects of biodiversity but do not capture its full scope. For instance, counting the number of different species focuses solely on species richness, which is one component of biodiversity. The total biomass of organisms speaks more to the quantity of life in an area, while genetic variation within a species touches on diversity at the genetic level but doesn't encompass the broader ecological context and interactions among different species and environments. Thus, the correct understanding of biodiversity as the variety of life in a specified area or ecosystem is broader and more encompassing than any singular aspect of biological diversity.