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Date November 2018 Marks available 1 Reference code 18N.3.SL.TZ0.13
Level Standard level Paper Paper 3 Time zone TZ0 / no time zone
Command term State Question number 13 Adapted from N/A

Question

A biotic index allows water pollution to be monitored without the need for a large number of chemical tests. Aquatic invertebrates are assigned pollution tolerance levels and these are used to assess water quality. The amount of each invertebrate species in the water is measured and this is used to calculate the index. The tolerance level of three invertebrate species is shown.

State which species could be found in mildly polluted water.

[1]
a.

State the name given to organisms whose presence or absence reflects an environmental condition.

[1]
b.

Distinguish between richness and evenness as components of biodiversity.

[1]
c.

Explain how edge effects can influence biodiversity in a region.

[2]
d.

Markscheme

dragonfly nymph AND midge larva (Both needed)
OR
all except mayfly ✔

a.

indicator species ✔

b.

richness is how many species there are in an area while evenness is how similar in number the populations of each species are ✔

c.

a. the edge of an ecosystem has different features from the centre ✔

eg: amount of wind, light

 

b. the edge has greater biodiversity ✔

c. it is an area of overlap between two ecosystems/habitats ✔

d. it has species from both ecosystems
OR
it has species not found in either ✔

e. reduction in biodiversity due to human interference ✔

d.

Examiners report

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

Syllabus sections

Option C: Ecology and conservation » Option C: Ecology and conservation (Core topics) » C.4 Conservation of biodiversity
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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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