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Question 23M.3.HL.TZ1.17

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Date May 2023 Marks available [Maximum mark: 6] Reference code 23M.3.HL.TZ1.17
Level HL Paper 3 Time zone TZ1
Command term Distinguish, Explain, Outline, Suggest Question number 17 Adapted from N/A
17.
[Maximum mark: 6]
23M.3.HL.TZ1.17

The Living Planet Index published by the World Wildlife Fund (WWF) tracks the state of global biodiversity by measuring the population sizes of thousands of vertebrate species around the world. The 2018 index shows an overall decline of 60 % in population size between 1970 and 2014. The chart shows the main threats to each taxonomic group in 2018.

[Source: WWF, 2018. Living Planet Report 2018: Aiming Higher. [PDF online]
Available at: https://www.wwf.org.uk/sites/default/
files/2018-10/LPR2018_Full%20Report.pdf, p. 73. Open access.]

(a)

Suggest a reason for the loss of bird habitats.

[1]

Markscheme
  1. deforestation/forest fires;
  2. clearing land for houses/farming/growth of cities;
Examiners report

Almost everyone received one mark here, usually for stating deforestation as a reason for loss of bird habitat.

(b)

Outline how in situ conservation may help preserve populations of amphibians.

[2]

Markscheme
  1. the amphibians are kept in their natural habitat;
    OR
    preserves habitat/resources for amphibians;
  2. area can be actively managed
    OR
    pollution/predators/alien species can be controlled in the area;
Examiners report

In general, candidates demonstrated a poor understanding of in situ conservation or were too general in their response. Those who did get a mark usually had a vague idea that it was related to natural habitat.

(c)

Distinguish between species richness and evenness as components of biodiversity.

[1]

Markscheme

richness is how many species are in an area, evenness considers the relative number of each species;

Examiners report

While candidates seemed to know what species richness was, they were not able to say what species evenness was and both were required for the one mark. Only a few candidates were thus awarded this mark.

(d)

Explain how an indicator species may help monitor pollution.

[2]

Markscheme
  1. indicator species used to assess a specific environmental condition;
  2. they are tolerant/sensitive to certain levels of pollutant;
  3. their presence/absence allows the level of pollution to be estimated
    OR
    relative numbers of indicator species used to calculate biotic index;
Examiners report

This question was poorly answered by many. Candidates struggled to explain clearly the role of indicator species in monitoring pollution, again giving very general responses.

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