Which statement differentiates species richness from species evenness?

• A. Richness is the count of species in an area; evenness is how evenly individuals are distributed among those species.
• B. Richness measures how many ecosystems are present; evenness measures the number of individuals per species.
• C. Richness is the count of species in an area; evenness is how equally individuals are distributed among those species.
• D. Richness is the total biomass; evenness is the rate of reproduction.

Answer: (A)

Biodiversity in a community is described by two related ideas: how many species are present and how the individuals are spread among those species. Richness is simply the count of different species in the area. Evenness looks at the distribution of individuals: if every species has about the same number of individuals, evenness is high; if a few species dominate with many individuals while others are rare, evenness is low.

The statement that richness is the count of species and evenness is how evenly individuals are distributed among those species captures this distinction clearly. Other options mix up what richness or evenness measure—one suggests richness is about ecosystems, which isn’t about the number of species; another ties evenness to the number of individuals per species in a way that doesn’t express the distribution pattern across all species; and entities like biomass or reproduction rate aren’t definitions of richness or evenness.