Back to the full dot-point answer
QLDBiologyQuick questions
Unit 3: Biodiversity and the interconnectedness of life
Quick questions on Measuring biodiversity: species richness, evenness and Simpson's index (QCE Biology Unit 3)
15short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is species richness (S)?Show answer
Species richness is the total number of different species in a defined area or sample.
What is species evenness?Show answer
Species evenness describes how evenly individuals are distributed among the species present.
What is simpson's diversity index (D)?Show answer
Simpson's diversity index combines richness and evenness into a single number between 0 and 1.
What is worked calculation?Show answer
A rockpool quadrat contains: limpets (n = 8), snails (n = 5), crabs (n = 2), barnacles (n = 5). Total N = 20.
What is how to calculate?Show answer
Count the species. That is it.
What is why it is limited?Show answer
Richness ignores abundance. A community of 3 species with abundances (12, 4, 1) has the same richness as one with (5, 6, 6), but they feel ecologically very different to anything living in them.
What is conceptually?Show answer
A community is most even when all species are equally abundant. A community dominated by one species, with the others rare, has low evenness even if richness is high.
What is interpretation?Show answer
D close to 1 means high diversity (a randomly selected pair of individuals is likely to belong to different species). D close to 0 means low diversity (most pairs belong to the same species, so one species dominates).
What is limited to one level of biodiversity?Show answer
Simpson's index quantifies species-level diversity in a single sample. It says nothing about genetic biodiversity within those species or about ecosystem-level diversity across the region.
What is sensitive to sample size and effort?Show answer
Rare species are easily missed. Larger and more numerous samples generally increase richness; index values from samples of different size are not directly comparable.
What is all species treated equally?Show answer
A keystone species, an introduced weed and a common native are counted the same. An ecosystem dominated by an invasive species can score a high Simpson's value while being ecologically degraded.
What is no information about ecosystem function?Show answer
Two communities with the same index can differ in productivity, nutrient cycling, pollination services and resilience.
What is spatial and temporal snapshot?Show answer
A single survey reflects one place at one time. Seasonal variation (flowering, migration, larval recruitment) can change the value substantially.
What is using N when you should use n?Show answer
Inside the bracket, use the number of individuals of each species (n). Outside, use the total (N).
What is forgetting the "1 minus" step?Show answer
The raw quotient is the probability that two individuals belong to the same species. Subtract from 1 to get the diversity index. Some textbooks use D = sum( n(n - 1) / N(N - 1) ) directly, where higher values mean lower diversity.