Date | November 2018 | Marks available | 1 | Reference code | 18N.3.HL.TZ0.15 |
Level | Higher level | Paper | Paper 3 | Time zone | TZ0 / no time zone |
Command term | Deduce | Question number | 15 | Adapted from | N/A |
Question
The graph shows a theoretical model that divides species into five ecological groups (I to V) related to the degree of tolerance to an increasing pollution gradient.
[Reprinted from Marine Pollution Bulletin, 40, A. Borja, J. Franco and V. Perez, 'A marine biotic index to establish the ecological quality of soft-bottom benthos within European estuarine and coastal environments', pp. 1100–1114, Copyright (2000), with permission from Elsevier. https://www.sciencedirect.com/journal/marine-pollution-bulletin]
The biotic index is calculated using the formula shown.
Identify the group that is most intolerant to pollution.
Deduce the meaning of ni in this formula.
Deduce the meaning of ai in this formula.
Outline how organisms in Group V could be used to measure pollution in an environment.
Markscheme
«group» I ✔
number of individuals of a species ✔
tolerance rating of that species ✔
a. group V organisms «could» contain indicator species ✔
b. group V organisms can survive in polluted environments «while others cannot» ✔
c. they have a high tolerance/BI index
OR
«relative number of» indicator species can be used to calculate the value of a biotic index ✔
d. the more group V present could indicate more pollution ✔
OWTTE
e. absence of group V could indicate a cleaner environment ✔