Question 18N.3.SL.TZ0.13
| Date | November 2018 | Marks available | [Maximum mark: 5] | Reference code | 18N.3.SL.TZ0.13 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Distinguish, Explain, State | Question number | 13 | Adapted from | N/A |
A biotic index allows water pollution to be monitored without the need for a large number of chemical tests. Aquatic invertebrates are assigned pollution tolerance levels and these are used to assess water quality. The amount of each invertebrate species in the water is measured and this is used to calculate the index. The tolerance level of three invertebrate species is shown.
State which species could be found in mildly polluted water.
[1]
dragonfly nymph AND midge larva (Both needed)
OR
all except mayfly ✔
State the name given to organisms whose presence or absence reflects an environmental condition.
[1]
indicator species ✔
Distinguish between richness and evenness as components of biodiversity.
[1]
richness is how many species there are in an area while evenness is how similar in number the populations of each species are ✔
Explain how edge effects can influence biodiversity in a region.
[2]
a. the edge of an ecosystem has different features from the centre ✔
eg: amount of wind, light
b. the edge has greater biodiversity ✔
c. it is an area of overlap between two ecosystems/habitats ✔
d. it has species from both ecosystems
OR
it has species not found in either ✔
e. reduction in biodiversity due to human interference ✔
