Water is one factor that affects the distribution of plant species. Outline three other factors that can also affect plant distribution.

temperature affects metabolism/enzyme activity/transpiration rate/germination / each plant species has an optimum temperature range;
light affects rate of photosynthesis/(time of) flowering;
soil pH affects absorption of minerals/enzyme activity / each plant has an optimum pH range / some plants require acid soil / some plants require alkaline;
salinity affects the osmotic potential / most plants function in narrow range of salinity / salts affect the water uptake by the plants;
mineral nutrients required for synthesis of organic molecules;
presence of (suitable) pollinator/dispersal organisms to aid reproduction;
distribution (number and type) of predators/herbivores/diseases/pathogenic organisms which harm plants;
competition from other plants (for resources);
other valid factor with brief outline;
Accept examples for each factor eg nitrates are necessary for protein synthesis.
Award [0] for a list of factors.

Most candidates were able to get 2 out of 3 marks in (b) for outlining factors that affect plant distribution, although some only listed 3 factors with no other detail given, which did not earn marks.