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20.3Human Influences on Ecosystems

Pollution — Cambridge IGCSE Biology 0610 Revision Notes & Topical Questions

5 min read 15 parts Lesson 3 of 5 1 quiz

📚 Cambridge IGCSE Biology 0610 Hub / Topical Revision
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Lesson summary

20.3 Pollution — IGCSE BIOLOGY notes: Describe the sources and effects of water, air and plastic pollution, including eutrophication and the enhanced greenhouse effect.PollutantSourceEffectUntreated sewageHuman waste entering rivers where treatment is lackingEutrophication and di…

  • Greenhouse gases
  • Carbon dioxide sources
  • Methane sources
  • Permafrost
  • Consequences
  • Persistence

Part 1 of 6Pollutants and their effects

PollutantSourceEffect
Untreated sewageHuman waste entering rivers where treatment is lackingEutrophication and disease
Fertilisers (nitrate, phosphate)Run-off from farmlandEutrophication
Carbon dioxideBurning fossil fuels; clearing and burning treesEnhanced greenhouse effect and climate change
MethaneCattle, rice paddies, landfillEnhanced greenhouse effect
Non-biodegradable plasticsLitter and packagingHarm to land and aquatic animals
Female contraceptive hormonesSewage waterFeminisation of male aquatic organisms and reduced sperm count

Part 2 of 6Eutrophication

1
Fertiliser or sewage runs into a lake or river, adding nitrate and phosphate.
2
Algae and water plants grow rapidly, forming an algal bloom.
3
The bloom blocks light, so plants below cannot photosynthesise and die.
4
Decomposing bacteria increase in number as dead organisms build up.
5
The bacteria respire aerobically and use up the dissolved oxygen.
6
Fish and other organisms needing dissolved oxygen die.

Part 3 of 6Air pollution and the greenhouse effect

1Greenhouse gases
  • Greenhouse gases carbon dioxide and methane act like a blanket, absorbing infrared radiated from the Earth.
2Enhanced greenhouse effect
  • Enhanced greenhouse effect more gas retains more heat.
3Carbon dioxide sources
  • Carbon dioxide sources burning fossil fuels and deforestation.
4Methane sources
  • Methane sources livestock, rice paddies and landfill.
5Permafrost
  • Permafrost warming melts it, releasing more trapped methane.
6Consequences
  • Consequences global warming, climate change, melting ice, sea level rise and extreme weather.

Part 4 of 6Plastic pollution in water

Persistence
  • Persistence non-biodegradable plastic cannot be broken down by decomposers.
Animals
  • Animals eat plastic or become entangled, leading to injury and death.
Microplastics
  • Microplastics broken-down plastic is swallowed by animals and enters food chains.
Toxins
  • Toxins breaking down plastic can release toxins that affect marine organisms.

Part 5 of 6Plastic pollution on land

Landfill
  • Landfill plastic is usually buried.
Toxins
  • Toxins as it breaks down it releases toxins into the soil.
Land use
  • Land use the land is unsuitable for crops or grazing and can only be built on decades later.

Part 6 of 6More from the specification

Biological oxygen demand as a monitoring means
  • Biological oxygen demand as a monitoring means incubating water samples over five days provides an analytical means to quantify organic sewage pollution in streams.
Eutrophication of Freshwater Ecosystems
  • Agricultural run-off of soluble nitrate and phosphate fertilisers sparks rapid algal blooms;
    • when algae die, saprotrophic bacterial decomposers proliferate and consume dissolved oxygen, asphyxiating fish and aquatic invertebrates.
Accumulation of Non-Biodegradable Plastic Wastes
  • Synthetic plastics persist in terrestrial and marine environments for centuries, breaking down into microplastics that enter trophic chains, entrap marine fauna,
    • and leach toxic endocrine-disrupting additives.
Acid Precipitation and Atmospheric Acidification
  • Sulfur dioxide and nitrogen oxides released during industrial fossil fuel combustion dissolve in atmospheric moisture to form sulfuric and nitric acids, lowering soil pH and leaching toxic aluminium ions into lakes.
Monoculture
  • Growing one type of crop on a large area.
Habitat destruction
  • Damage or removal of the places where organisms live.
Captive breeding
  • Breeding endangered species in zoos or reserves.
Intensive farming
  • Producing as much food as possible from limited land and resources.
Species
  • A group of organisms that can reproduce to produce fertile offspring.
Biodiversity
  • The number of different species in an area.
Sustainable
  • Able to continue without damaging resources for the future.
Conservation
  • Protecting species and habitats.
Habitat
  • The place where an organism lives.
Endangered
  • At risk of extinction.
Population
  • A group of organisms of one species in the same area at the same time.

Key terms

TermMeaning
EutrophicationExcess nutrients causing algal growth, plant death, decomposition and oxygen loss.
Algal bloomRapid growth of algae on the surface of water.
Greenhouse gasA gas that traps heat, such as carbon dioxide or methane.
MicroplasticA very small particle formed as plastic breaks down.
Non-biodegradableNot able to be broken down by decomposers.

Avoid these mistakes

1
Saying fertiliser kills fish directly — it causes algal growth and the fish die from oxygen depletion.
2
Saying eutrophication is caused by too much oxygen — it ends in oxygen depletion.
3
Saying the greenhouse effect itself is harmful — the natural effect keeps Earth warm and the enhanced effect causes the problem.
4
Saying plastic rots away — it is non-biodegradable and persists as microplastics.

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