QUESTION 32 (6 marks)
Equal-sized samples from two rock pools contain the animals shown. Use .
a) Calculate Simpson’s diversity index for each pool. Show working and give values to three decimal places. [3 marks]
b) Compare species richness and evenness in the two samples. [2 marks]
c) State which pool has greater species diversity and justify using your results. [1 marks]
Practice marking scheme
Answer
a) Pool P: 0.789; pool Q: 0.500. b) Both have richness 4; P is more even. c) P has greater species diversity.
Working
Each sample has . For P, , so . For Q, the sum is , so . Both contain four species, but Q is dominated by species A. P therefore has greater evenness and a higher index.
Marking criteria
- Uses the finite-sample formula with N = 20. [1 mark]
- Calculates SDI for P as 0.789. [1 mark]
- Calculates SDI for Q as 0.500. [1 mark]
- Identifies equal richness of four. [1 mark]
- Identifies greater evenness in P. [1 mark]
- Identifies P as more diverse and links this to its higher index. [1 mark]
Practice question aligned to the current QCAA syllabus; review the worked solution and marking criteria.
View the QCAA syllabusCompare your working with the guide above.