Simpson's Index of Diversity accounts for which two factors?

Simpson's Index of Diversity is a widely used measure in ecology that quantifies the biodiversity of a community. The correct answer highlights two crucial factors: species richness, which refers to the number of different species in a given area, and species evenness, which describes how evenly the individuals are distributed among those species.

Species richness alone gives a count of the types of species present but does not provide information about their relative abundances. On the other hand, species evenness considers the distribution of individuals among the species. Together, these two aspects provide a comprehensive view of community diversity. A community with high species richness but low evenness could be less diverse than a community that has lower richness but greater evenness, as it indicates that no single species dominates the population.

This combination of richness and evenness allows researchers and conservationists to assess the health and stability of ecosystems effectively. In contrast, the other options focus on factors that do not directly contribute to measuring biodiversity in the same integrative manner that species richness and evenness do.