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Date May 2015 Marks available 1 Reference code 15M.2.SL.TZ2.3
Level Standard level Paper Paper 2 Time zone Time zone 2
Command term State Question number 3 Adapted from N/A

Question

The image shows a forest food web from North America.

Describe what is meant by a food chain.

[2]
a.

Identify a food chain with four or more organisms from the forest food web.

[1]
b (i).

Deduce the trophic level of each organism identified in your food chain from (b)(i).

[1]
b (ii).

State one reason that the population of mountain lions is smaller than the populations of other animals in the food web.

[1]
c.

Markscheme

a. food chain shows feeding/trophic relationships;
b. showing which organism/animal eats which organism;
c. showing the flow of energy from producer/autotroph to top consumer/top carnivore / through trophic levels;

a.

example from the food web with four or more organisms, given in proper sequence with arrows showing flow of energy in the correct direction and starting with a producer.
Award [0] if any organism in the food chain is not in the web diagram.

b (i).

correct trophic levels

eg: raspberry bush⎯⎯→chickadee ⎯⎯→bull snake⎯⎯→mountain lion
        producer                 primary            secondary        tertiary consumer
                                      consumer          consumer

Accept ECF for mistakes in previous part. Do not accept “trophic level 1” etc.

b (ii).

mountain lions/highest trophic level receives less energy as energy is lost at each level / mountain lions are larger than other animals and require more (smaller) individuals for food.

c.

Examiners report

Most gained at least 1 mark for their description of a food chain.

a.

Most students were able to pick a suitable food chain from the web given. However a significant number seemed to ignore the web given and draw one from memory. There were a few with the arrows reversed and not starting with a producer.

b (i).

The naming of the trophic levels is given in 5.1.7, and these are expected.

b (ii).

In c most were able to give a valid reason.

c.

Syllabus sections

Core » Topic 4: Ecology » 4.1 Species, communities and ecosystems
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