Practice question

Pielou-type evenness near zero means individuals are distributed very unequally among species. One or a few species account for most observations while the remainder are rare; equal abundances would instead drive the standardized index toward its upper limit of one. Diversity has separable richness and evenness components. Shannon entropy rises when species number increases or abundances become more equal, while Pielou evenness scales Shannon entropy against the maximum possible value for that richness. Simpson measures emphasize the probability that sampled individuals belong to the same or different species, depending on convention. Every calculation therefore requires explicit relative abundances and a stated formula; comparing values produced under different conventions can reverse interpretation. In this context, the keyed term, Dominance by few species, identifies the relevant mechanism or quantitative relationship and links the observed pattern to its underlying ecological cause. The distinction is testable by measuring changes in organisms, resources, or process rates through time rather than relying on the label alone.