1. Ecosystems and Energy Flow
Chapter 5

2. Energy flow All life on Earth depends on sunlight
As sunlight enters the ecosystem it drives photosynthesis
Which uses the light to make sugar
6 CO2 + 6 H2O + sunlight  C6H12O6 + 6 O2
Carbon Dioxide
Water
Sugar
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3. Energy Flow Organisms that use photosynthesis are known as producers
They make their own food
Autotrophs (self-feeder)
Producers make-up the bottom of the food chain
Producers are then eaten by consumers
Get energy by eating others
Heterotrophs (other-feeder)
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4. Energy Flow There's 1 exception to the need of sunlight:
1977 scientists make it to the bottom of the ocean
They find that there is a ton of life at the very bottom
Since there is no light, how do they get energy
Plants use hydrogen sulfide coming out of the hydrothermal vents
This is extremely toxic to all of the rest of life on Earth
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5. Energy Flow There are 4 types of consumers: Herbivore Carnivore
Eats producers
Vegetarians, cows, sheep, deer
Carnivore
Eats other consumers
Meatarians, lions, hawks, snakes
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6. Energy Flow Omnivore Decomposer Eats both producers and consumers
Most humans, bears, pigs
Decomposer
Breaks down dead organisms
Fungi, bacteria
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7. Energy Flow Producers use the sun's energy to create food
When consumers eat they use the food to create energy using cellular respiration
This is the opposite of photosynthesis
C6H12O6 + 6 O2  6 CO2 + 6 H2O + energy
Water
Sugar
Sugar
Carbon Dioxide
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8. Energy Flow When a consumer eats another organism, it gains energy
The simplest sequence showing the transfer of energy is represented in a Food Chain
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9. Energy Flow While Food Chains are nice, ecosystems are not simple
Many things rely on the same organism to survive
A more accurate representation of the transfer of energy is a Food Web
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10. Energy Flow
Each time energy is transferred in an ecosystem, the energy moves up a Trophic Level
90% of all energy at a trophic level goes to keeping the organism alive
The other 10% is stored and can be transferred up to the next level
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11. Energy Flow Think of the energy loss like a pyramid
The “Producers” Level has 1000 times the amount of energy than is at the Top of the pyramid
These are all different Trophic Levels
More Energy = More Organisms
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12. Cycling of Materials The Carbon Cycle
Movement of carbon from the environment to organisms and back
Carbon atoms make up the basic structure of ALL organisms
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13. Cycling of Materials
Producers pull in CO2 from the atmosphere or the water (marine life) during photosynthesis
It is turned into sugars and stored (becomes part of the organism)
Consumers then gain carbon atoms when they eat the producers
The carbon atoms are stored until cellular respiration
During cellular respiration carbon is released back into the atmosphere
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14. Cycling of Materials
When organisms die the carbon is released into the soil
If conditions are right, after millions of years this carbon will become fossil fuels (coal, oil, natural gas)
Human are currently digging up as much fossil fuel as possible to burn for energy
When fossil fuels are burned it releases CO2
However, we are not putting the carbon back into the ground as fast as we are taking it out
This leads to global warming
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15. Cycling of Materials The Nitrogen Cycle
The movement of nitrogen from the environment to organisms and back
All organisms must have nitrogen create proteins and new cells
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16. Cycling of Materials 78% of the air is nitrogen
However, most organisms (including humans) cannot use the nitrogen that is in the air
We must rely on nitrogen-fixing bacteria to convert the nitrogen into a form we can use
This bacteria lives in the roots of bean and pea plants
Once the nitrogen is “fixed” it is stored in producers
And is transferred to consumers when they are eaten
When an organism dies the nitrogen is then returned to the soil
Where other bacteria turn it back into nitrogen gas
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17. Cycling of Materials The Phosphorus Cycle
Movement of phosphorus from the environment to organisms and back
This is a very slow cycle, and usually doesn't involve the air
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18. Cycling of Materials
Phosphorus is needed by all organisms to create new cells
This cycle starts with rocks that contain phosphorus
As the rocks erode, small amounts of phosphorus go into the soil and water
Plants will take in phosphorus from the soil
And Consumers take it in by eating the producers
Once in the water it will sink to the bottom
This sediment will turn into new rock formations
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19. Cycling of Materials
Nitrogen and Phosphorus are the 2 most important ingredients in fertilizers
When we use fertilizers, some of it is washed away before plants can use it
When it enters the water algae starts to grow
So much grows that it creates a thick layer of green muck on top of the lake
The algae grows so much that it takes up all of the oxygen from the water and kills all of the organisms
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20. How Ecosystems Change Ecological Succession Primary Succession
A gradual change in the types of species in a community
2 types: Primary and Secondary
Primary Succession
Occurs on a surface where an ecosystem has never existed
Rocks/cliffs, parking lots, volcanic islands
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21. How Ecosystems Change Secondary Succession
Occurs where an ecosystem previously existed
Rebuilding of ecosystems destroyed by floods, fire, earthquakes, farmland, …
Mount St. Helens (1980)
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22. How Ecosystems Change
The first organisms to start rebuilding are known as pioneer species
Usually mostly weeds, and plants that can survive harsh environments
These organisms make the land livable for other species
Eventually the ecosystem will stabilize into a Climax Community
A final and stable community
This ecosystem will not change a lot over time
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23. How Ecosystems Change
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24. How Ecosystems Change
One of the biggest debates about succession is over forest fires
Fires are a natural part of an ecosystem
Clean out brush, germinate seeds, enrich the soil
Of course fires also threaten homes, business, and communities
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