Cycles in an Ecosystem

1
Cycles in an Ecosystem

• Chapter 25.3

2
Cycles

• All organisms need certain substances to live,
  grow, and reproduce.

3

• Many substances, such as water, pass through
  natural cycles in which they are used and reused.

4
Some cycles include nonliving things.

• Many of the chemicals move in and out of the
  living realm.

5
The Water Cycle

• Water moves continually throughout the earth by
  means of the water cycle.

6
evaporation

• Energy from the sun changes water from a liquid
  to a gas through the process of evaporation.

7
condensation

• water vapor changes back to a liquid by the
  process of condensation.

8
precipitation

• The condensed water forms clouds, steam, or fog,
  and eventually falls back to the earth as
  precipitation.

9
The Nitrogen Cycle

• Nearly 80 percent of the earth's atmosphere is
  made up of nitrogen.
• Changing atmospheric
• nitrogen into usable compounds is called
• nitrogen fixation.

10
The Oxygen-Carbon Dioxide Cycle

• When you inhale, you take in air that contains
  oxygen.
• When you exhale, you release carbon dioxide back
  into the atmosphere.

11

• Another way in
• which carbon dioxide
• enters the atmosphere
• and becomes part of
• the cycle is through
• the decay of dead
• organisms.

12

• Sometimes the bodies of dead organisms do not
  decompose.