How is biodiversity defined?

Biodiversity is defined as the variety and variability of life forms within a given ecosystem. This encompasses not just the number of different species, but also the genetic diversity within those species and the variety of ecosystems themselves. Biodiversity is crucial for the stability of ecosystems, as it allows for a wider range of responses to environmental changes and stresses, supporting essential ecosystem processes such as nutrient cycling, pollination, and resilience against diseases.

Focusing solely on the number of species in a habitat captures only a part of biodiversity, as it neglects the genetic diversity and the interrelationships among species. The total mass of living organisms in an ecosystem, while important in ecological studies, does not reflect the complexity of biodiversity itself. Similarly, the rate of extinction of species is a concerning aspect of biodiversity loss but does not define what biodiversity is. In essence, the definition encapsulated in the correct option emphasizes the multidimensional nature of life forms and their interactions within ecosystems.