Chapter 21-Natural Resources

Ecosystems A balanced ecosystem is stable A change in one part of an ecosystem can change the whole thing Ex.: if the mice population disappears, the owl population will decrease

Changes to Ecosystems Can be caused by humans Can be caused by nonnative species Ex.: zebra mussels in the Great Lakes

Changes to Ecosystems Short term – seasonal Long term- volcanic eruptions, temperature changes Climatic changes – ice ages, interglacial periods

Energy and Resources The sun is the source of all energy Fossil fuels are formed from the remains of dead plant and animals long ago They are nonrenewable

Fossil fuels Most of our energy comes from burning them

Alternative energy Sources These are sources that do not burn fossil fuels Geothermal and nuclear are 2 other sources

Why Alternative Energy Sources? Fossil fuels cause major pollution, especially carbon dioxide.

Recycling and Conservation These are two ways to reduce the use of fossils fuels and reduce pollution