IB Biology HL C4.2.5 Supply to Decomposers Questions

Analyse how detritus feeds microbial communities, how bacterial decomposition releases carbon and nutrients, and how changing detritus alters food-web populations in IB Biology HL C4.2.5.

Exam points

Trace detritus and dead organic carbon from organisms or sediments to microbial and decomposer communities as a food and energy source.
Explain how bacterial or saprotrophic decomposition returns carbon as CO₂ and inorganic nutrients, including reduced decomposition and peat formation in anaerobic or waterlogged conditions.
Evaluate how changing detritus supply alters decomposer, producer and consumer populations through food-web and light-availability effects.

[Maximum number: 1]

Marine sediments form at the bottom of oceans. These sediments contain organic material from the surface waters. Scientists analysed samples drilled from the floor of the north Pacific Ocean, representing 86 million years of sedimentation. Graph A shows the data for oxygen concentrations in 28 metres of sediment and graph B shows the oxygen consumption per cell in 22 metres of sediment measured in femtomoles ( $\mathrm{fmol}=10^{-15} \mathrm{~mol}$ ).

Figure for Question IB Biology HL C4.2.5 Supply to Decomposers Questions question 1 — IB Biology HL

State a possible source of food for the microbial community in the sediments.

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IB Biology HL C4.2.5 Supply to Decomposers Questions question 1