A group of ecologists investigated the biodiversity of butterflies in three different ecosystems: ancient woodland, organic farmland, and urban parkland. During the study, they collected specimens of various species, including Pieris brassicae\textit{Pieris brassicae}Pieris brassicae, Pieris rapae\textit{Pieris rapae}Pieris rapae, and Vanessa cardui\textit{Vanessa cardui}Vanessa cardui.
State what is meant by the term 'species richness'.
Explain what the scientific names of Pieris brassicae\textit{Pieris brassicae}Pieris brassicae, Pieris rapae\textit{Pieris rapae}Pieris rapae, and Vanessa cardui\textit{Vanessa cardui}Vanessa cardui suggest about the evolutionary relationships between these three butterfly species.
The ecologists decided to calculate the index of diversity for each ecosystem. Explain why measuring the index of diversity is more useful than measuring species richness alone.
