DP Biology (last assessment 2024)

Test builder »

Question 18N.3.HL.TZ0.15

Select a Test
Date November 2018 Marks available [Maximum mark: 6] Reference code 18N.3.HL.TZ0.15
Level HL Paper 3 Time zone TZ0
Command term Deduce, Identify, Outline Question number 15 Adapted from N/A
15.
[Maximum mark: 6]
18N.3.HL.TZ0.15

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]

(a)

Identify the group that is most intolerant to pollution.

[1]

Markscheme

«group» I ✔

The biotic index is calculated using the formula shown.

BI = Σ ( n i × a i ) N

(b.i)

Deduce the meaning of ni in this formula.

[1]

Markscheme

number of individuals of a species ✔

(b.ii)

Deduce the meaning of ai in this formula.

[1]

Markscheme

tolerance rating of that species ✔

(c)

Outline how organisms in Group V could be used to measure pollution in an environment.

[3]

Markscheme

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 ✔

Syllabus sections