Draw a labelled diagram showing the ultrastructure of a typical prokaryote.

Outline how three different environmental conditions can affect the rate of photosynthesis in plants.

Explain how the emission of gases, both naturally and through human activity, can alter the surface temperature of the Earth.

Award [1] for each structure clearly drawn and correctly labelled, up to [4 max].
cell wall – a uniformly thick wall;
pili – hair-like structures / flagellum – at least length of the cell;
plasma membrane – represented by a continuous single line; May be labelled as the innermost wall line.
ribosomes – drawn as small discrete circles/shaded circles;
nucleoid – region with DNA not enclosed in membrane;
plasmid – circular ring of DNA;
cytoplasm – the non-structural material within the cell;

Award [3 max] if one eukaryote structure is shown, [2 max] for two eukaryote structures, [1 max] for three eukaryote structures and [0] if four or more eukaryote structures are shown.

light: [2 max]
rate increases with increasing light;
it reaches maximum then plateaus;
as all chloroplast molecules are working at optimal pace;

temperature: [2 max]
rate increases with increasing temperature;
to a maximum/optimum temperature;
but then falls off rapidly;
as enzymes are denatured above the optimal temperature;

carbon dioxide: [2 max]
rate increases with increasing carbon dioxide level;
it reaches maximum then plateaus;
as photosynthesis operating at optimal level;

Award any of the above points if clearly drawn in a diagram.

increase in temperature is called global warming;
this is caused by the greenhouse effect;
a natural phenomenon that has occurred over millions of years;
main gas responsible is carbon dioxide;
other gases like methane/nitrous oxide also cause effect;
shortwave radiation from the Sun enters atmosphere;
warms the surface of the Earth;
longwave radiation emitted by the surface of the Earth;
is absorbed by carbon dioxide/greenhouse gases;
human use of fossil fuels has increased levels of atmospheric carbon dioxide;
rapid rise in temperatures over (approximately) hundred years;
cows/animals/peat bogs release methane;
greenhouse gases emitted by volcanic activity;

On the whole the diagrams of a prokaryotic cell were well drawn receiving full marks. A sizable number of candidates drew hybrid cells with features of prokaryote and eukaryotes. Contradictions in answers cannot be rewarded and such answers did poorly. As with other questions, some candidates squandered the opportunity for marks by drawing small or untidy diagrams

This question was straight from the subject guide but many candidates were unable to identify the relevant factors. Those who could generally did well. Many good answers used annotated graphs to illustrate the changing effect of the factor on photosynthesis.

The impact of gases on the Earth’s temperature was, in most cases, not well answered with many candidates confusing the greenhouse effect with the hole in the ozone layer.