CAIE IGCSE Biology 20.2.3 Through Altering Food Webs and Food Questions

Trace how pesticides and herbicides can harm non-target species, remove aquatic producers and disrupt food chains.

Exam points

describe how pesticides can harm non-target species, disrupt food chains and reduce biodiversity
trace how herbicides entering lakes can kill aquatic producers, reduce food for herbivores and lower biodiversity

[Maximum number: 4]

Some crop farmers use herbicides on their fields.
Fig. 4.1 shows a farmer spraying a rice crop with herbicides.

Fig. 4.1

Fields of crop plants were sprayed with two herbicides. A farmer measured the concentration of the two herbicides, A and B, in a lake near the fields.

The water in the lake was sampled at intervals for two weeks.
Fig. 4.2 shows the results.
concentration of herbicides in the lake water samples / mg per kg

Fig. 4.2

Suggest how herbicides damage ecosystems in a lake.

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CAIE IGCSE Biology 20.2.3 Through Altering Food Webs and Food Questions question 1