IB Biology HL 3.4.5 Coral Reef Change Question Bank

Practise IB Biology HL 3.4.5 by interpreting coral-cover data and explaining how warming and carbon dioxide affect reef-building corals.

Exam points

Interpret coral-cover data to evaluate the effect of rising ocean temperature.
Explain how higher carbon dioxide affects calcium-carbonate reef construction.

[Maximum number: 2]

Increasing carbon dioxide concentration in the atmosphere leads to acidification of the ocean. This in turn reduces the amount of dissolved calcium carbonate. A study was undertaken to investigate the effect of increasing the concentration of atmospheric carbon dioxide on the calcification rate of marine organisms. Calcification is the uptake of calcium into the bodies and shells of marine organisms. The study was undertaken inside Biosphere-2, a large-scale closed mesocosm. The graph shows the results of the data collection.

Figure for Question B4.1.5—Coral reef formation conditions question 1 — IB Biology HL

Outline one way in which reef-building corals are affected by increasing atmospheric carbon dioxide.

Alternative 1

a. corals have parts/shells/«exo»skeleton made of calcium carbonate

b. calcium carbonate «shells» dissolve in acid conditions

c. acid/high $\mathrm{CO}_{2}$ conditions reduces availability of calcium carbonate «for forming shells» OR negatively affects enzymes involved in calcification

Alternative 2

d. $\mathrm{CO}_{2}$ is «significant» greenhouse gas causing rise in ocean temperatures

e. higher ocean temperatures/acidification leads to rejection of zooxanthellae OR higher ocean temperatures/acidification leads to coral bleaching

2 max

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B4.1.5—Coral reef formation conditions question 1