Describe how a transect can be used to investigate the distribution of plant species in this ecosystem.

The vegetation shown here has developed as a result of primary succession. Outline the changes that take place in the abiotic environment during primary succession.

Outline the abiotic factors that affect the distribution of plant species in an ecosystem.

a. random positioning of the transect;
b. transect is a line stretched over an area of study;
c. samples taken/species present recorded at regular intervals along the transect;
d. used to investigate effect of an abiotic variable/named example;

a. rocks begin to break down;
b. minerals begin to accumulate;
c. soil begins to develop;
d. water retention increases;
e. erosion of soil is reduced (by rhizoids and roots);

The question asks for an outline but most candidates have given a list of factors without a reason. Therefore award [1] for every two factors listed or [1] for each qualified factor.

water (distribution) for turgor/biochemical reactions/photosynthesis;
mineral / inorganic content / salinity of soil/water;
temperature (max, min, range, seasonal changes) / altitude;
light (intensity, duration, wavelength) for photosynthesis;
pH (range, average, changes) of soil/water;
wind (direction, strength);

As in previous years, many candidates did not know what a transect is or its purpose and some were evidently confused with estimating a population size.

In (b) many answers described the vegetative changes in succession rather than the abiotic.

The mark scheme in (c) was generous in allowing lists of factors and/or elaborations, otherwise many would not have scored here.