Explain6 marksChallenge
An ecologist compared two woodland fragments, X and Y, in a nature reserve. She placed 50 random quadrats (each 1 m²) in each fragment and recorded the number of individuals of every plant species present. Using these data, she calculated Simpson's index of diversity (D) for each fragment. The formula for Simpson's index is:
D = 1 – Σ (nᵢ / N)²
where nᵢ is the number of individuals of species i, and N is the total number of individuals of all species.
Fragment X had D = 0.34. Fragment Y had D = 0.88.
Explain what these D values indicate about the biodiversity of the two fragments and why random sampling was essential for this comparison.