Effects of environmental change (HT ONLY)

Environmental changes affect the distribution of species in an ecosystem and may be seasonal, geographic, or caused by human interaction.

Change	Explanation	Example
Temperature	Enzymes have an optimum temperature at which they function.	Seasonal: seasonal decreases in temperature can cause migrations, e.g. towards winter, birds, such as swallows, migrate south from Northern Europe toward hotter temperatures.
Availability of water	No life can exist without water.	Geographic: in deserts, cacti and camels have adapted to survive with minimal water, and most life and green plants are found surrounding oases (where water rises from underground sources). The distribution of algal species also varies depending on the tide.
Composition of atmospheric gases	Combustion of fossil fuels release gases that can be toxic to organisms (e.g. oxides of carbon, sulfur and nitrogen).	Human interaction: most lichens will only grow in high numbers in clear air as they are sensitive to air pollution. The distribution of species can be a useful bioindicator of air pollution.

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