Pollution is a harmful change in the natural environment caused by human activities:
This may be the release of substances which are toxic to either animals or plants, or it may be the release of energy (heat, light, radiation, or sound) which interferes with the development of animals or plants.
Pollution is usually harmful to one or more species of animal or plant. However, releasing nutrients into rivers may be beneficial to some organisms while it is harmful to others.
Here are some general examples:
- automobile exhaust emissions
- oil spills
- the dumping of industrial wastes in the water supply
- the overuse of pesticides
- the overuse of chemical fertilizers
- improper disposal of solid wastes
Releasing raw sewage into a river causes pollution. Sewage contains lots of organic substances which are a source of food for bacteria and fungi. The result is that the bacteria and fungi thrive. Since they use up all the oxygen in the water, most of the animals will die.
Pollution may occur naturally, as when an erupting volcano emits sulphur dioxide, but the term usually refers to the negative effect of human activities.
I hope that you will be able to remember most of the facts on this page, but you must memorise the definition of pollution. Write it on a small index card. Put the red words on one side of the card and the blue ones on the other. Add the card to your revision pack.
Pollution: is a harmful change in the natural environment caused by human activities. (now add some examples of your own choice; e.g. oil spillage at sea (Sea Empress), fertilizer run off into rivers.