Practice question

Species richness is the count of distinct species present in a defined community, area, or sample. A community containing twenty species has greater richness than one containing ten, regardless of how individuals are distributed among them. Evenness addresses that distribution: it is high when species have similar abundances and low when one or a few dominate. Dominance likewise concerns concentration of abundance, while an index combines selected components mathematically. Shannon and Simpson measures therefore can differ between communities that have identical richness but different evenness. Richness estimates depend strongly on sampling effort, area, season, detectability, and taxonomic resolution. Rarefaction or standardized coverage is often used to compare samples of unequal size, and unseen-species estimators can account for taxa likely missed. Richness also has no information about species identity: two communities may each contain ten species yet share none, producing equal richness but high beta diversity. Despite these limitations, it is the simplest and most intuitive biodiversity component and forms the basis of species–area curves, local alpha-diversity comparisons, and regional conservation inventories.