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Question 23M.3.SL.TZ2.15

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Date May 2023 Marks available [Maximum mark: 3] Reference code 23M.3.SL.TZ2.15
Level SL Paper 3 Time zone TZ2
Command term Compare, Explain Question number 15 Adapted from N/A
15.
[Maximum mark: 3]
23M.3.SL.TZ2.15

Two small fields of the same size were sampled to determine the biodiversity of the wild plants found in them.

(a)

Using the data in the table, compare the richness of the two fields.

[1]

Markscheme

equal as there are the same number of species;

Examiners report

There was some confusion regarding the terms richness, so many lost the mark in (a).

(b)

The Simpson’s reciprocal index of diversity for each field is shown in the table. Explain the significance of these values in terms of the ecosystem.

[2]

Markscheme
  1. Field 1 has the greater biodiversity (as it has the higher value);
  2. (likely) a more stable ecosystem (than Field 2)
    OR
    more ecological niches (than Field 2)
    OR
    more complex food webs (than Field 2)
    OR
    more evenness (than Field 2);
Examiners report

There was some confusion regarding the terms evenness and Simpson's diversity index, so many got only 1 mark in (b). Most candidates did not understand that they needed to explain Simpson's reciprocal index in terms of Field 1 and Field 2 and describe what the Simpson's reciprocal index indicated.