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Date May 2010 Marks available 3 Reference code 10M.3.SL.TZ1.27
Level Standard level Paper Paper 3 Time zone Time zone 1
Command term Outline Question number 27 Adapted from N/A

Question

Outline three factors that affect plant distribution.

[3]
a.

Outline a method used to correlate the distribution of plant species with an abiotic factor.

[2]
b.

Markscheme

plant distribution closely linked to levels of abiotic factors in the environment;
given organism can survive only within a certain temperature range to which it is adapted;
water is a limiting factor in most terrestrial ecosystems and plants are classified according to ability to tolerate water shortage;
most plants can only tolerate narrow pH range;
light intensity/quality/wavelength and duration/photoperiod are important for photosynthesis;
most plants cannot tolerate large fluctuations in salinity/high salinity;
mineral nutrients affect plant fertility/soil structure/water retention;
Accept ONE correct reference to herbivore activity

a.

transect used when there is a transition in habitats and populations;
description of use of a line or belt transect;
height variation/light intensity/salinity/various abiotic factors can be recorded;
along the transect, along with sampling of plant and/or animal species present;

b.

Examiners report

Many candidates did not “outline” the factors, but merely stated them. Consequently, they did not give enough detail to gain marks.  There was also some confusion between distribution and dispersal (ie of seeds). Where points had been elaborated, they were often superficial, and references to light were common, rather than the required light intensity or wavelength.

a.

Poorly answered on the whole, suggesting that candidates may not have sufficient experience of actual fieldwork on which to base their knowledge.

b.

Syllabus sections

Option C: Ecology and conservation » Option C: Ecology and conservation (Core topics) » C.1 Species and communities
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