IB Biology HL C4.2.5 Supply to Decomposers Questions

Decomposers obtain energy from carbon compounds in detritus. Dead organisms, faeces, fallen leaves and shed tissues supply the organic matter they use. In IB Biology HL C4.2.5, questions ask what feeds microbial decomposers and how a change in detritus can affect organisms in the food web.

Exam points

Identify dead organic matter, including detritus from organisms, as a source of carbon compounds and energy for decomposers.
Use food-web evidence to predict how an increase in detritus can affect detritus feeders and organisms that feed on them.

[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