1. Chapter 5: How Ecosystems Work
Ecology
Chapter 5: How Ecosystems Work

2. Section 1: Energy Flow in Ecosystems
Life ultimately depends on the sun! Energy enters ecosystems as radiant energy from the sun.
Photosynthesis
6H20 + 6CO2 + sunlight C6H12O6 + 6O2
Cellular Respiration
C6H12O6 + 6 O2  6H2O + 6CO2 + ATP
Energy exits ecosystems as heat

3. Matter Cycles & Energy Flow
Biosphere
Carbon
cycle
Phosphorus
cycle
Nitrogen
cycle
Water
cycle
Oxygen
Cycle
Figure 3.7
Natural capital: life on the earth depends on the flow of energy (wavy arrows) from the sun through the biosphere and back into space, the cycling of crucial elements (solid arrows around ovals), and gravity, which keeps atmospheric gases from escaping into space and helps recycle nutrients through air, water, soil, and organisms. This simplified model depicts only a few of the many cycling elements.
Heat in the environment
Heat
Heat
Heat

4. Producers/Autotrophs
Use light energy to make their own food through photosynthesis

5. Consumers/Heterotrophs
Cannot make their own food. Instead, they get energy by feeding on other organisms

6. Types of Consumer
Herbivore—gets energy by eating producers

7. Omnivore
Gets energy by eating producers and consumers

8. Carnivore
Gets energy by eating consumers

9. Decomposer
Get energy by breaking down dead organisms

10. Energy Transfer
Energy is transferred from one organism to another through feeding relationships
Food Chains/Webs
Purpose – shows how energy & nutrients move from one organism to another through the ecosystem
Show energy flow through feeding relationships
Direction: grass  cow  human

12. Trophic Levels Each step in a food chain is a trophic level
How many trophic levels are in this food chain?

13. Energy Loss
Energy is lost as its transferred from one trophic level to the next
Energy Pyramids show energy loss

14. 10% Rule
Only 10% of the energy in a given trophic level is passed to the trophic level above it

15. Consequences of Energy Loss
What happens to population size as one moves from lower trophic levels to higher trophic levels?

16. Section 3: How Ecosystems Change
Ecological Succession
The gradual process of change in the make-up of a community
The final stable community is called the climax community
Our climax community is an oak hickory forest
The type of climax community differs depending on where you are in the world

18. Saguaro national park Tucson

19. Grassland Montana

20. Primary Succession Primary succession begins on bare rock or sand
The first organisms are pioneer species
Key idea: succession begins without soil

21. Pioneer Organisms Examples include lichens, mosses and dune grass
As these organisms break apart rock, die and decompose soil begins to form.
This process changes the conditions of the environment making it suitable for new organisms

25. As new organisms move into the area the conditions continue to change making the area suitable for an even greater variety of organisms
This process continues until a climax community is achieved

27. Secondary Succession
When a community undergoes a disturbance and succession occurs again it is called secondary succession
Examples of disturbances include: fire, storms, farming, foresting
A disturbance doesn’t remove the soil
Key idea: succession begins with soil already in place.

32. Old Field Succession
Secondary succession that occurs after a farm is abandoned