Question 19M.3.SL.TZ2.12e
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.3.SL.TZ2.12e |
| Level | SL | Paper | 3 | Time zone | TZ2 |
| Command term | Outline | Question number | e | Adapted from | N/A |
A survey was made of the intertidal zone at Butter Lump Bay, Great Cumbrae, Scotland. The three species of barnacle found were Elminius modestus (EM), Chthamalus montagui (CM) and Semibalanus balanoides (SB). The kite diagram shows the vertical distribution of these three species from the low tide mark at 0 m to 2.25 m above low tide.
[Source: reprinted from Estuarine Coastal and Shelf Science, 152, M C Gallagher, et al., The invasive barnacle species,
Austrominius modestus: Its status and competition with indigenous barnacles on the Isle of Cumbrae, Scotland,
pages 134–141, 2014 with permission from Elsevier]
Barnacles are sensitive to pollution. Outline how it might be possible to use these organisms as indicator species.
[2]
a. indicator species need particular environmental conditions
OR
indicator species tolerate only certain environmental conditions ✔
b. increase/decrease in population size «over time» shows effect of environmental conditions ✔
c. used to calculate biotic index/index of cleanliness ✔
d. index of 10/high index number indicates totally unpolluted
OR
index of 2 or 1/low index number indicates severe pollution ✔
In part (e) some candidates chose to describe invasive species in general (without using the data) and others described the data but were not able to attach this to the idea of an invasive species. Many repeated the information given in the question.
