IB Biology SL A4.2.1 Biodiversity Definition Questions

Distinguish species richness from evenness, calculate Simpson diversity from species counts, and interpret biodiversity differences between communities.

Exam points

Distinguish species richness as the number of species from species evenness as the similarity of their population sizes.
Calculate Simpson’s reciprocal diversity index from species counts and show the numerator, denominator and final value.
Interpret a higher Simpson index as greater community biodiversity and compare richness, evenness or stability between sites or sampling times.
Use quadrats or transects, species and individual counts, richness, evenness and Simpson index to quantify biodiversity change over time.

[Maximum number: 1]

The tundra ecosystem in Finnish Lapland has a short growing season and a mean temperature of $-2.0^{\circ} \mathrm{C}$ . It is also naturally grazed by herbivores such as reindeer (Rangifer tarandus). Different quadrats were set up to include and exclude the reindeer in both normal and warmed temperatures. Open-topped warming chambers were used to heat both the soil and air in the warmed quadrats. The graph shows the changes in plant richness over five years.

Figure for Question IB Biology SL A4.2.1 Biodiversity Definition Questions question 1 — IB Biology SL

State what is meant by species richness.

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IB Biology SL A4.2.1 Biodiversity Definition Questions question 1