NSF Senior Science Bee Practice Exam

Species diversity refers to the variety of different species that exist within a specific area, alongside their relative abundance. It is a crucial aspect of biodiversity and reflects the ecological health of an environment. High species diversity typically indicates a rich ecosystem with various interactions among organisms, contributing to resilience and stability.

In this context, while the total number of organisms in any given habitat points towards the overall population density, it does not directly address the variety of species present. Similarly, the variety of ecosystems within a region pertains to ecosystem diversity rather than focusing specifically on species. Lastly, the number of endangered species highlights a conservation concern but does not encompass the concept of species diversity as it relates to both the presence and abundance of all species within an area. Thus, the most accurate definition of species diversity is the one that measures both the number of different species and their respective abundances within a particular habitat.