Biodiversity and populations practice

Answer
B

Working
The biological species concept uses actual or potential interbreeding and reproductive isolation. Its interbreeding criterion cannot be applied directly to organisms that reproduce only asexually.

Marking criteria

• Select B. [1 mark]

Answer
a) Ecosystem: the three habitat types; species: 32 bird species; genetic: bill-colour alleles within ducks. b) Species richness omits genetic and ecosystem variation.

Working
Biodiversity can be described at several levels. Distinct ecosystems contribute ecosystem diversity; the number and relative abundance of species contribute species diversity; variation in alleles within a species contributes genetic diversity. A bird-species count measures one component of species diversity and provides no direct measurement of within-species genetic diversity or the diversity of ecosystem types.

Marking criteria

• Links the different habitat types to ecosystem diversity. [1 mark]
• Links the 32 bird species to species diversity. [1 mark]
• Links within-species alleles to genetic diversity. [1 mark]
• States that a species count does not measure genetic diversity. [1 mark]
• States that a species count does not measure ecosystem diversity or species evenness. [1 mark]

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 $N=20$. For P, $\sum n(n-1)=4(5\times 4)=80$, so $SD{I}_P=1-80/380=0.789$. For Q, the sum is $14(13)+3(2)+2(1)+1(0)=190$, so $SD{I}_Q=1-190/380=0.500$. 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]