1. Chapter 21-Natural Resources

2. 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

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

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

5. 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

6. Fossil fuels
Most of our energy comes from burning them

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

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

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