Species Diversity
The variety and relative abundance of different species within an ecosystem or biome.
Formula
Shannon Index (H) = −Σ(pᵢ × ln pᵢ)
Real World
Surveys of the Great Barrier Reef before and after coral bleaching events in 2016–2017 showed fish species richness dropped by up to 40% on severely bleached reefs, demonstrating how a single stressor can rapidly reduce species diversity.
Exam Focus
Distinguish species richness (number of species) from evenness (relative abundance) — confusing these two components is a common mark-losing error.
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