What two types of material does untreated sewage introduce into aquatic ecosystems?
Organic waste and nutrients.
Cambridge IGCSE (9–1) Biology 0970 (Extended) (2026–2028) · 20.3
Revise Cambridge IGCSE (9–1) Biology 0970 (Extended) (2026–2028) specification point 20.3, Pollution, with free active-recall flashcards. Flip through the set or review every question and answer below.
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What two types of material does untreated sewage introduce into aquatic ecosystems?
Organic waste and nutrients.
Why does decomposition of sewage-derived organic matter reduce dissolved oxygen?
Microorganisms use dissolved oxygen in respiration as they decompose the organic matter.
What can happen to aquatic animals if dissolved oxygen falls sufficiently?
They may be unable to obtain enough oxygen and die.
How can nutrients from untreated sewage further reduce dissolved oxygen?
They promote algal growth, increasing the material decomposers break down and thus further reducing dissolved oxygen.
Which two human activities release carbon dioxide into the air?
Burning fossil fuels and deforestation.
What are two sources of methane emissions?
Livestock and the decay of organic waste.
How do carbon dioxide and methane reduce the rate at which energy escapes to space?
They absorb some of the infrared radiation emitted by Earth.
What effect do higher concentrations of carbon dioxide and methane have on the greenhouse effect and global temperature?
They strengthen the natural greenhouse effect, raising global temperatures.
What changes in climate patterns can result from the enhanced greenhouse effect?
Changes in temperature and rainfall patterns.