O-LevelBiologyEcology & Environment5090/21 · May/June 2018 · Q110 Marks

The diagram shows a food web in a pond. kingfisher, small fish, frog, tadpole, water beetle, snail, water plant.

(a)(i)Complete the table by writing the correct number of organisms for each statement about the food web. The first number has been written for you. statement number the number of producers 1 the number of consumers the number of herbivores the number of carnivores the number of food chains[4]
(a)(ii)Draw and label a pyramid of biomass for one food chain from the food web.[2]
(b)The pond may become polluted by fertilisers containing nitrogen. Explain how this pollution might affect the population of frogs in the pond.[4]

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Mark scheme

Marking points from the official mark scheme (May/June 2018). The mark or mark type is shown in brackets.

[4] (1) 6; 3; 3; 3;
[2] correct shape; correct labels ;
[4] more plants / growth of plants / more leaves / algal bloom AW ; eutrophication ; reference to nitrate production for protein; decomposition / O2 used or respiration by bacteria; more food for water beetle / snail; less food for water beetle / snail; more food for frogs; less food for frogs ; population of frogs increases ; population of frogs decreases ;

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