How is biodiversity defined?

Biodiversity is best defined as "the variety of life in a particular habitat or ecosystem." This definition encompasses not only the number of different species present but also includes the variety of ecosystems and the genetic diversity within those species. Biodiversity is crucial for the resilience and functioning of ecosystems, as it contributes to their stability, productivity, and ability to adapt to changes.

The concept of biodiversity is broad and considers various levels, including species diversity, ecosystem diversity, and genetic diversity. This is why the response highlighting the variety of life in a habitat or ecosystem is the most comprehensive and accurate.

While counts of endangered species or genetic variation are important aspects of biological study, they do not fully encompass the complete definition of biodiversity. Similarly, total biomass may indicate the abundance of life but does not reflect the variety or richness of species within an ecosystem. Thus, the correct answer captures the essence of what biodiversity represents.