1. Chapter 5
How Ecosystems Work

2. Energy Flow in the Ecosystem
Almost all energy comes from the sun.
an exception to this rule is deep ocean organisms that use hydrogen sulfide as an energy source.
energy from sun is used either directly (to producers) or
indirectly (to consumers).

3. Energy Flow in the Ecosystem
Energy is used directly by PRODUCERS - organisms that make their own food. (also called autotrophs)
producers play a crucial role in recycling nutrients by allowing carbon to enter the Carbon Cycle.
PHOTOSYNTHESIS
6CO H2O C6H12O6 + 6O2
products
reactants
Carbon Dioxide (from the atmosphere) and water in the presence of sunlight and chlorophyll react and produce a glucose molecule and oxygen. Only done by producers.

5. Energy Flow in the Ecosystem
All organisms use energy from photosynthesis by
CELLULAR RESPIRATION
C6H12O6 + 6O CO2 + 6H2O + Energy
Is photosynthesis in reverse.
Oxygen is reactant and Water and Carbon Dioxide are the products
Produces energy
Where photosynthesis takes carbon from the atmosphere and stores it in glucose, Cellular Respiration returns it to the atmosphere, completing the Carbon Cycle

6. Consumers
Energy is passed from producers to Consumers - organisms who get energy from eating other organisms. (also called heterotrophs).
1. Herbivore - a type of consumer who eats only producers.

7. Consumers
2. Carnivores – are consumers who eat only other consumers.

8. Consumers
Some carnivores are scavengers- carnivores who feed on dead consumers.

9. Consumers
3. Omnivores - organisms that eat both producers and other consumers.

10. Consumers
4. Decomposers - organisms that breakdown biotic material and recycling nutrients into the ecosystem.

11. Energy Flow in the Ecosystem
Energy flows through feeding relationships.
Can be shown through Food Chain and Food Web.
The food chain shows the feeding relationship from one organism to another.

12. Energy Flow in the Ecosystem
The food web is more accurate because it shows all the feeding relationships in an ecosystem.

13. Energy Flow in the Ecosystem
it is important to understand how energy flows because of Biological Magnification- a process that results in a higher accumulation of pollutants in the higher order consumers in an ecosystem.
For Example
Each step along the energy flow is called a Trophic Level.
Energy flow can also be represented in an Energy Pyramid.

14. Energy Pyramid Producers 1 10 100 1000
Only 10% of energy moves up from each level. 90% is used in daily functions like
Decomposers found at all trophic levels
digestion and movement.
Tertiary
hawk 1
Consumers
Could be omnivore but usually carnivore
Secondary Consumers 10
sparrow
Could be carnivore or omnivore
100
grasshopper
Primary Consumers -
Always herbivores
Producers
1000
grass

15. Recycling Nutrients The Carbon Cycle
The two main processes fueling the short term carbon cycle are – photosynthesis and cellular respiration.
In the long term cycle, some carbon becomes carbonates (coral in the ocean/limestone on land) and some becomes fossil fuels- coal, oil, and natural gas.
Pesky Homo sapien has increased the CO2 level by 30% since the start of the Industrial Revolution.

17. Recycling Nutrients The Nitrogen Cycle
Gaseous nitrogen is not usable by organisms.
Nitrogen – fixing bacteria in soil (found also on roots of legumes) converts gaseous nitrogen to ammonia. (lightning can do it too)
Other bacteria in soil then convert ammonia to nitrates and nitrites.
Producers then take in nitrogen from soil. Consumers get their nitrogen by eating producers.
Decomposers breakdown organisms or waste and converts nitrogen back to gaseous form

19. Recycling Nutrients The Phosphorous Cycle
Phosphorous is weathered from rocks and ends up in soil or water.
Decomposers breakdown dead organisms or waste and deposit phosphorous in soil or water.
Excess phosphorous (from fertilizer runoff or natural causes) can cause Eutrophication -a condition where a build up of nutrients causes algal blooms and oxygen depletion in the water.

23. Acid Precipitation
Is formed when Nitric/Sulfuric Acid is released into the atmosphere through the burning of fossil fuels or excessive amounts of wood.
Normal pH of rain is Considered acid rain if less than 5.6
11= Ammonia (basic) 7= Neutral 2= Lemon Juice (Acidic)
Causes $5 billion per year in damages.

25. How Ecosystems Change
Ecological Succession is a gradual change in an ecosystem.
Primary Succession - occurs where no previous ecosystem exists. ( soil formation must occur and soil will not contain large organic material cast off of organisms)
1. Pioneer Species - Lichens can grow on bare rock.
2. Grasses
3. Shrubs
4. Conifers
5. Hardwoods
Until reach Climax Community – stable if left alone.
Could take a long time or a shorter time depending on which ecosystem you are dealing with.

26. How Ecosystems Change
Secondary Succession occurs where soil is present in an ecosystem that has been damaged. Takes less time than primary.

27. Secondary Succession (cont.)
Another example is Mt. St. Helens

28. Secondary or Old-Field
Succession

29. Old Field Succession
Occurs where a cultivated field is left fallow.

30. The End