Revision - GCSE Biology - The Greenhouse Effect and Pollution Problems

Atmospheric pollutions

  • Fossil fuels – When coal, natural gas and oil are burnt they created carbon dioxide which contributes to the greenhouse effect. It comes primarily from industry, Power Station and cars, and also release sulphur dioxide and nitrogen oxides which cause acid rain. The main greenhouse gasses are carbon dioxide, methane and water vapour.
  • CFCs (chloro fluoro carbons) – These come from aerosols, fridges air con units and polystyrene. These create holes in the ozone which let harmful UV rays in.
  • Lead in petrol – This comes from 4 star petrol and damages the nervous system
  • Deforestation also contributes to the greenhouse effect because
    • The burning of the trees releases lots of carbon dioxide
    • The decrease in the number of trees leads to less carbon dioxide being converted into oxygen via photosynthesis

The greenhouse effect

  • The temperature of the earth is controlled by the balance of infra red radiation from the sun being absorbed by the earth, and being reflected out
  • With more greenhouse gasses, the atmosphere becomes thicker, and becomes an insulating layer
  • This layer traps heat, and stop it being reflected back out into space.
  • The main gasses which cause this are methane and carbon dioxide
  • This gradual heating up could cause drought, and also floods as the ice caps melt meaning the water levels of the sea would increase. It would also lead to extreme weather and wide scale animal migrations
  • The CO2 levels used to be balanced because plants take it in, and animals produce it. However, now, because there are fewer plants and much more carbon dioxide due to industry the levels of carbon dioxide are gradually increasing
  • The industrial revolution and the massive amounts of fossil fuels burnt in the last 100 years are what has probably led to this rise
  • Methane is created naturally by marshlands. However, paddy fields and cattle ranches are causing levels to increase


Ways to reduce this

  • We should reduce car emissions – Use public transport, share cars, use more efficient engines, look for alternative power sources
  • Reduce the amount of fossil fuels burnt – Use an alternative source of power wind, solar, wave etc
  • Reduce deforestation
  • To reduce the hole in the ozone layer – Reduce aerosols

Acid Rain

  • Acid rain is also a problem
  • When car fuel is burnt sulphur dioxide and other various nitrogen oxides are produced
  • When these mix with clouds they dissolve into the water and form sulphuric and nitric acid. This then falls as acid rain
  • Cars and power stations are mainly to blame
  • Acid rain then turns lakes into acidic pools of death which can kill fish and has a serious effect on the ecosystem
  • It causes aluminium salts (which are in the ground) to dissolve into the lake and become aluminium ions which are poisonous to many fish
  • It also kills trees and damages limestone buildings
  • It is prevented by clearing up emissions. Acid gas scrubbers are used in industry and catalytic converter are used with cars. Reducing burning of fossils fuels is also effective

Other pollution

  • Water pollution – Eutrophication, sewage is also bad as it gets into the food chain (like pesticides) and also causes eutrophication like problems (lots of microbes). Oil spills, heat pollution increased microbe activity hot water from industry re-injected into the sea, the warm conditions cause microbes to bloom

Also See

Here are the other comprehensive GCSE Biology notes by Prometheus: