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Date November 2018 Marks available 1 Reference code 18N.2.SL.TZ0.3
Level Standard level Paper Paper 2 Time zone TZ0 / no time zone
Command term Identify Question number 3 Adapted from N/A

Question

Boreal forests stretch across Canada, Russia and Scandinavia. This northern ecosystem accounts for 29 % of the world’s forest areas. The long, cold winters favour tall evergreen trees with either needles or scale-like leaves. These trees are wind-pollinated and their seeds are not enclosed in a fruit. The photograph shows a typical boreal forest in winter.

Identify the dominant plant phylum in the boreal forest.

[1]
a.

In some areas there are gaps in the boreal forest where trees fail to grow and peat tends to accumulate. Suggest reasons for this.

[2]
b.

An increase in global temperatures poses a critical threat to boreal forests. Explain the consequences of climate change to this northern ecosystem.

[2]
c.

The boreal forests are situated close to the north pole and even in summer the intensity of sunlight is lower than at the equator. Sketch a graph showing the effect of light on the rate of photosynthesis, labelling the axes.

[2]
d.

Markscheme

coniferophyta/conifer/coniferous/gymnosperms/pinophyta ✔

a.

a. waterlogged soil/poor drainage
OR
acidic soil
OR
anaerobic conditions/soil ✔

b. organic matter is not «fully» decomposed «leading to peat formation»
OR
decomposers/saprotrophs less active/fewer in cold «temperatures» ✔

b.

a. higher temperatures so more transpiration/droughts/dehydration/water shortage ✔

b. more forest fires ✔

c. more/new pests/diseases because of the changed conditions ✔

d. competition from trees/plants «that colonize/spread to boreal forests» ✔

e. trees/«named» organisms «of boreal forests» not adapted to warmer conditions
OR
trees/«named» organisms migrate/extend range due to the warmer conditions ✔

f. trees die so there is loss of habitat for animals ✔

g. faster decomposition/nutrient cycling «so conditions in the ecosystem change» ✔

h. standing water/floods due to more snow/permafrost melting ✔

c.

a. x-axis labelled as light intensity/amount of light AND y-axis labelled as rate of photosynthesis/rate of oxygen release/rate of carbon dioxide uptake ✔

b. curve starting at/slightly to the right of the x-axis origin and rising rapidly and then more slowly and plateauing but never dropping ✔

d.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.
[N/A]
d.

Syllabus sections

Core » Topic 5: Evolution and biodiversity » 5.3 Classification of biodiversity
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