AQA GCSE Biology

Revision Notes

7.2.6 Impact of Environmental Change

Higher Tier Only

Changing Environments

  • Environmental change (often as a result of human activity) can affect the distribution of species within ecosystems. Being able to evaluate these changes when provided with appropriate information is an important biological skill
  • Changes in the environment can cause the distribution of living organisms to change
  • A change in distribution means a change in where an organism lives
  • Some changing environmental factors that can affect the distribution of organisms include:
    • Temperature
    • Availability of water
    • Composition of atmospheric gases
  • These changes may be seasonal, geographic or caused by human interaction
Higher Tier Only

Effects on Distribution

Temperature

  • Organisms have adaptations that enable them to survive within a certain temperature range
  • As climate change occurs and average temperatures rise, the distribution of species is changing
  • Eg. the distribution of some plant, bird and insect species in Europe is spreading northwards into areas they were not previously able to inhabit, as these areas now have higher average temperatures as a result of global warming

Worked example effect of temperature on distribution of plants_1, downloadable IGCSE & GCSE Biology revision notes

Worked example effect of temperature on distribution of plants_2, downloadable IGCSE & GCSE Biology revision notes

Availability of water

  • All organisms require water to survive, either directly (water is essential for the biological processes that sustain living organisms) or indirectly (water may provide a habitat for species and is essential for the growth of plants that support whole food chains and food webs)
  • Eg. every year in Africa, wildebeest migrate first northwards and then southwards again, following the rainfall as this provides them with fresh grazing and water

Composition of atmospheric gases

  • There are many ways in which the distribution of organisms can be affected by atmospheric gases:
    • Oxygen is required for aerobic respiration in plants and animals
    • Some aquatic animals (such as fish) can only survive in water with high oxygen concentrations
      • As pollution increases in freshwater systems, growth of anaerobic microorganisms is encouraged which can lead to a drop in oxygen when they die as a result of decomposition, fish cannot survive in these conditions
    • Carbon dioxide is required for photosynthesis in plants (CO2 concentration affects the rate of photosynthesis)
    • Some species are very sensitive to air pollution
      • Eg. some species of lichen are not able to grow where sulphur dioxide is present (produced during certain industrial processes due to the combustion of fossil fuels)

Exam Tip

You should be able to evaluate the impact of environmental changes on the distribution of species in an ecosystem given appropriate information.

When answering questions that refer to a chart, graph or table, remember to reference specific figures from the data to support your answer, as seen in the worked example above.

Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.
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