State the process occurring at X and Y. 

X: ..................................................................

Y: ..................................................................

Suggest one type of organism that can be involved in process Z.

Explain the relationship between the rise in concentration of atmospheric carbon dioxide and the enhanced greenhouse effect.

X: combustion / burning;
Y: photosynthesis;

(saprotrophic) bacteria/fungi / saprotrophs
Award [0] for decomposers

carbon dioxide is a greenhouse gas (naturally produced by organisms);
human activity has increased the normal level of CO₂/caused enhanced greenhouse effect;
short-wave radiation from the Sun is re-radiated as longer wave radiation/ infrared/heat;
infrared/heat captured by greenhouse gases/CO_2;
Accept any of the above points shown in a clearly annotated diagram.

Many students were confused by the large schematic diagram, and did not understand the word „process‟ in part a. They were not able to state that X is combustion/burning and that Y was photosynthesis.

Due to the fact that "decomposition‟ was in the stem, "decomposers‟ was not allowed in part b. Saprotrophs/bacteria or fungi were accepted.

The hole in the ozone layer seemed to be well known in the South American centres. Unfortunately this has nothing to do with the answer expected in part c about the enhanced greenhouse effect! Few seemed to distinguish between the short wavelength/high frequency UV rays from the Sun and the long wavelength/low frequency IR rays reflecting back through the thickening atmosphere.