| Date | November 2010 | Marks available | 4 | Reference code | 10N.3.SL.TZ0.18 |
| Level | Standard level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Explain | Question number | 18 | Adapted from | N/A |
Question
Explain the consequences of releasing raw sewage into rivers and the involvement of microorganisms in this process.
Markscheme
a. eutrophication;
b. algal bloom deprives other organisms of light;
c. death of organisms;
d. microorganisms/decomposers increase oxygen demand/BOD;
e. causing deoxygenation of river;
f. formation of hydrogen sulphide/ammonia/nitrites;
g. which are toxic to some organisms;
h. pathogenic organisms released into water;
Examiners report
Some good answers gaining 3 or 4 marks were seen for this section on the consequences of releasing raw sewage into rivers. However, there was still quite a bit of confusion with ideas not being clearly expressed.
Syllabus sections
Option B: Biotechnology and bioinformatics » Option B: Biotechnology and bioinformatics (Core topics) » B.3 Environmental protection
Show 63 related questions
