The Impact of Environmental Changes (OCR Gateway GCSE Biology)

Higher Tier Only

The Impact of Environmental Changes

• Measuring abiotic factors and how they change is an important discipline in biology (and geography)
• Measuring the abundance and distribution of animals and plants also provides data on species distribution
• However, it is important to be able to link the two types of data
  • In order to identify how environmental changes can cause species distributions to change
• This is important for humans, as the dominant species on Earth so they can encourage biodiversity-friendly trends and stop trends that damage biodiversity

Assessing Pollution

• It is possible to use the presence or absence of particular organisms as an indicator of pollution
  • For example, some organisms are particularly sensitive to certain changes in their environment
  • This means they can be studied in order to determine the effect of human activities on a particular habitat or ecosystem
  • These organisms are known as indicator species
• Indicator species can be used to determine the level of:
  • Water pollution
  • Air pollution

Water pollution

• One form of water pollution occurs when raw sewage or fertilisers (both containing nitrates) is released into a body of fresh water, such as a stream or pond
  • This causes microorganisms in the water to increase in number
  • As these microorganisms respire, they use up the oxygen in the water
• Some invertebrate species, such as stonefly larvae and freshwater shrimps, are highly sensitive to the concentration of dissolved oxygen of the water they are living in
  • This makes them good indicator species for water pollution
  • For example, the presence of stonefly larvae in a stream or river indicates that the water is not polluted (i.e. it is clean and has high oxygen levels)
• By contrast, some other invertebrate species are adapted to live in polluted environments
  • This also makes them good indicator species for water pollution
  • For example, the presence of bloodworms and sludge worms in a body of water suggests a very high level of water pollution

Air pollution

• Lichens (that grow on trees and buildings) can be used as an indicator species for air pollution
• This is due to the fact that some lichen species are highly sensitive to sulfur dioxide concentrations in their environment
  • Sulfur dioxide is one of the air pollutants released from car exhausts and power stations (i.e. during the combustion of fossil fuels)
• The abundance (number) and type of lichen species growing at a particular location can be monitored to determine how clean the air is
  • For example, a high abundance of lichen indicates clean air
  • In particular, a high abundance of bushy lichen species indicates very clean air (as these lichens need cleaner air than crusty lichen species)
• Another indicator species for air pollution is blackspot fungus, which grows on rose leaves
• Like lichen, it is also sensitive to sulfur dioxide concentrations and its presence indicates clean air

Potential disadvantages of using indicator species

• Although using indicator species is a fairly simple and cost-effective method of determining whether a habitat is polluted or not, it has some drawbacks
  • For example, it can't give accurate numerical (quantitative) figures for exactly how much pollution is present
  • In addition, the presence or absence of indicator species can also be affected by biotic factors other than pollution (e.g. the presence of predators or disease)
• If more detailed information on pollution levels is required, non-living indicators can be used instead
  • For example: dissolved oxygen meters and chemical tests can be used to very accurately determine the concentration of dissolved oxygen in the water and can be used to show changes in levels of water pollution over time
  • Electronic meters and laboratory tests can be used to very accurately determine the concentration of sulfur dioxide in the air and can be used to show changes in levels of air pollution over time

The evidence for the impact of environmental changes on the distribution of organisms

• All of the below abiotic factors have been linked to changes in the distribution of organisms on Earth
  • Availability of water
  • Gases in the atmosphere
  • Global temperatures
  • Sea level effects
  • Patterns of wind and storms

Water availability

• Changes in rainfall patterns can affect the species that thrive in wet climates, for example
  • Some plants (eg. cactus species) are very well adapted to dry climates, so if these become wetter, the cactus will be outcompeted by other species
• Monsoon seasons affect the life cycles of certain plants that live in affected countries
  • Changes to rainfall patterns may be harmful to those species

Atmospheric gases

• Pollution
• CO₂ levels
  • The greenhouse effect is caused by more CO₂ in the atmosphere from burning fossil fuels
  • Because plants use CO₂, this may benefit certain species that can carry out photosynthesis more efficiently
  • CO₂ in the atmosphere causes the greenhouse effect, and global warming

Temperature

• CO₂ insulates the Earth, preventing heat energy from being reflected back out to space
• Global temperatures are on the rise - the most prominent measure of climate change
• This causes polar ice to melt and seawater to expand
  • Warmer ocean water can also dissolve less CO₂ so that gets released into the air
    • Think about what happens if you warm up a cold Coke - it loses its fizz quickly

Sea level effects

• • Melting ice and seawater expansion cause rising sea levels
  • Rising sea levels threaten low-lying areas with flooding
    • Especially when combined with violent storms which are becoming more frequent and widespread
  • This is worrying because many of the world's main human population centres are in coastal or low-lying cities
    • e.g. Tokyo, Seoul, Shanghai, New York, Jakarta, London, Mumbai and many others

The Greenhouse Effect - How it Affects Global Temperatures