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Date May 2018 Marks available 2 Reference code 18M.3.HL.TZ1.15
Level Higher level Paper Paper 3 Time zone Time zone 1
Command term Compare and contrast Question number 15 Adapted from N/A

Question

A retreating glacier leaves an environment of lifeless glacial deposits, including sands and gravels. Retreating glaciers often offer suitable sites for primary succession.

State one abiotic factor that will determine the type of ecosystem in a succession.

[1]
a.

A retreating glacier leaves an environment of lifeless glacial deposits, including sands and gravels. Retreating glaciers often offer suitable sites for primary succession.

Predict the process of succession that takes place on exposed bare ground as the glacier retreats.

[3]
b.

Compare and contrast food chains and food webs.

[2]
c.

Markscheme

temperature/precipitation/rainfall/minerals /pH of soils/light/humidity/wind/slope (in this specific example)

a.

a. (bare ground) colonized by microorganisms/pioneer species

b. thin soil forms from rock fragments / decomposing organisms

c. soil retains water from melting permafrost/ice

d. grasses/small plants/herbaceous plants/moss grow

e. (larger plants) create habitat for animals

f. weather/climate may limit plant size/biodiversity

OR

climax community forms

b.

Similarities:

a. in both food webs and chains organisms are arranged by trophic levels/feeding positions 

b. both represent the transfer of food/energy in an ecosystem 

c. both include producers and consumers 

Differences:

d. one species could occupy different trophic levels in a food web but not in a food chain / converse 

e. food chain represents one possible feeding option for each organism but food web represents more possible feeding relationships/trophic levels

OWTTE
(max 1 for similarities)
(max 1 for differences)

c.

Examiners report

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

Syllabus sections

Option C: Ecology and conservation » Option C: Ecology and conservation (Core topics) » C.2 Communities and ecosystems
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Option C: Ecology and conservation » Option C: Ecology and conservation (Core topics)
Option C: Ecology and conservation

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