1. Chapter Five: How Ecosystems Work

2. Section One: Energy Flow in Ecosystems
Life Depends on the Sun
Energy enters the ecosystem through photosynthesis
Photosynthesis: plants use sunlight to make sugar molecules
Solar energy helps change carbon dioxide and water into sugar and oxygen

3. Section One: Energy Flow in Ecosystems
Producers and Consumers
Producer: an organism that makes its own food
Also called a autotroph
Consumer: organisms that get their energy by eating other organisms
Also called a heterotroph

4. Section One: Energy Flow in Ecosystems
What eats what?
Herbivores: Consumers that eat only producers
Carnivores: Consumers that eat only herbivores
Omnivores: Consumers that eat producers, herbivores, and carnivores

5. Section One: Energy Flow in Ecosystems
Decomposers
Consumers that get their food by breaking down dead organisms
Examples are bacteria and fungi

6. Section One: Energy Flow in Ecosystems
Cellular Respiration
The process of breaking down food to yield energy
Sugar and oxygen combine to yield carbon dioxide and water

7. Section One: Energy Flow in Ecosystems
Energy Transfer
Occurs each time one organism eats another
Food Chains and Food Webs
Food Chain: a sequence in which energy is transferred from one organism to the next
Food Web: shows many feeding relationships that are possible in an ecosystem

8. Section One: Energy Flow in Ecosystems

9. Section One: Energy Flow in Ecosystems
Trophic Levels: each step through which energy is transferred
Each time energy is transferred from one organism to another, some of the energy is lost as heat and less energy is available to organisms at the next trophic level

10. Section One: Energy Flow in Ecosystems
How energy loss affects an ecosystem?
There are fewer organisms at the higher trophic levels
The loss of energy between trophic levels limits the number of trophic levels

11. Section Two: The Cycling of Materials
The Carbon Cycle
A process by which carbon is cycled between the atmosphere, land, water, and organisms

12. Section Two: The Cycling of Materials

13. Section Two: The Cycling of Materials
How humans affect the carbon cycle
Burning fossil fuels by cars, power plants, and factories
Increased carbon dioxide could lead to global warming

14. Section Two: The Cycling of Materials
The Nitrogen Cycle
A process in which nitrogen is cycled between the atmosphere, bacteria, and other organisms
All organism need nitrogen to build proteins
Nitrogen-fixing bacteria: bacteria that fix atmospheric nitrogen into chemical compounds
Decomposers and the Nitrogen Cycle
Break down decaying and dead materials and return nitrogen to the soil

15. Section Two: The Cycling of Materials

16. Section Two: The Cycling of Materials
The Phosphorus Cycle
The movement of phosphorus from the environment to organisms and then back to the environment
Part of the cells of many organisms

17. Section Two: The Cycling of Materials
Fertilizers and the Nitrogen and Phosphorus Cycles
Excessive fertilizers can enter the water as runoff
Causes algae growth which causes an algal bloom
Algal blooms can deplete the water of nutrients

18. Section Three: How Ecosystems Change
Ecological Succession: the gradual process of change and replacement of some or all of the species of a community
May take hundreds or thousands of years
Primary Succession: the type of succession that occurs on a surface where no ecosystem existed before
Secondary Succession: occurs on a surface where an ecosystem has previously existed
More common type

19. Section Three: How Ecosystems Change
Primary Succession

20. Section Three: How Ecosystems Change
Secondary Succession
Occurs in ecosystems that have been disturbed or disrupted by humans or animal or by natural processes such as storms, floods, earthquakes, or volcanoes
Pioneer species: the first organism to colonize any newly available area and begin the process of ecological succession
Climax community: a final and stable community

21. Section Three: How Ecosystems Change

22. Section Three: How Ecosystems Change
Old-field Succession
A type of secondary succession
Occurs when farm land is abandoned