O-LevelBiologyEcology & Environment5090/21 · Oct/Nov 2020 · Q311 Marks

Atmospheric air contains several gases.

(a)Complete the table to show the approximate percentage of each gas listed. | gas | percentage in atmospheric air | |----------------|-------------------------------| | carbon dioxide | | | oxygen | | | nitrogen | |[3]
(b)(i)Name a gas not listed in the table which will be present in a higher concentration in an industrial region than in the countryside.[1]
(b)(ii)Explain why this gas will be present in a high concentration in an industrial region.[3]
(c)Suggest why there are usually fewer species of wildlife in industrial regions than in the countryside.[4]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2020). The mark or mark type is shown in brackets.

[1] (CO₂) 0.03–0.04 ;
[1] (O₂) 20–21 ;
[1] (N₂) 78–80 ;
[1] oxides of nitrogen / of sulfur / carbon monoxide ;
[1] human activity, e.g. power station / factories / manufacturing / cars / machines ;
[1] fossil fuels / named fossil fuel;
[1] burnt / combustion ;
[1] air / water + pollution / contamination ;
[1] less food for animals / fewer types of food for animals ;
[1] deforestation / roads / buildings + reduced habitat AW ;
[1] disposal of wastes ;
[1] named waste, e.g. mercury ;
[1] acid rain AW ;

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