Biology 9700 · AS & A Level · Investigation of limiting factors

Investigation of limiting factors — practice question

The banana plant, Musa acuminata, is a tall herbaceous species with very large leaves. An investigation was carried out to find the net carbon dioxide uptake of a banana plant at different light intensities. Fig. 6.1 shows a banana plant. Fig. 6.2 presents the investigation results, with mean net carbon dioxide uptake measured in $\mu\text{mol m}^{-2}\text{s}^{-1}$ plotted against light intensity in lux.
(a(i))[3]

Using Fig. 6.2, describe and explain the results at a light intensity of 1000 lux.

(a(ii))[3]

Using Fig. 6.2, describe and explain what can be concluded from the graph at light intensities between 2000 lux and 7000 lux.

(a(iii))[1]

Explain why the rate of carbon dioxide uptake levels off as light intensity rises above 10 lux.

(b(i))[1]

In contrast to the Venus fly trap, pitcher plants do not use moving parts to trap insects. Insects are drawn in by scent made at the top of the pitcher. After entering the pitcher, the insect slips to the bottom and into a liquid that contains digestive enzymes. Suggest a type of enzyme found in the pitcher plant that is used to digest insects.

(b(ii))[2]

Pitcher plants live in bogs and wet grassland where the soil has a low concentration of minerals such as nitrates. The plants gain nitrates from the digestion of insects. Calvin cycle intermediates are used to make more complex compounds, some of which require nitrogen from nitrates. Name one compound that requires nitrogen from nitrates and name the Calvin cycle intermediate from which it is synthesised.

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: “CO$_2$ uptake is below zero / net CO$_2$ release ($-1.6\,\mu mol\,m^{-2}\,s^{-1}$)” …

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