1. Do NOW…
How do we (humans) get “energy”? What’s the name of the process?
What do we need energy for?

2. Section 5.3- Energy Flow in Ecosystems

3. The Importance of Energy
All organisms need energy for growth, movement, maintenance, repair, and reproduction.
In an ecosystem, energy flows
SUN Autotrophs Heterotrophs
With respects to energy, the Earth is an open system. But it cannot exchange matter. 3

4. A) Autotrophs
A groups of organisms that can use the energy in sunlight to convert water and carbon dioxide into glucose (food) process of PHOTOSYNTHESIS
Autotrophs are also called Producers because they produce all of the food that they need and heterotrophs use.
Without autotrophs, there would be no life on this planet.
Examples: Plants and Algae (and some bacteria and protists) 4

5. Autotrophic Organisms5

6. Specialized Autotrophs
Chemotrophs (Chemoautotrophs)
Autotrophs that get their energy from inorganic substances, such as salt, to make carbohydrates
Live deep down in the ocean where there is no sunlight, near hydrothermal vents
Example: Bacteria, Deep Sea Worms 6

7. B) Heterotrophs Organisms that do not make their own food
Another term for Heterotroph is a consumer because they consume other organisms in order to get their energy.
Examples: Rabbits, Deer, Mushrooms, Bears, Vultures, Shrimp 7

8. Heterotrophs 8

9. Classification of Heterotrophs
Detrivores (Scavengers)- feed on the tissue of dead/dying organisms examples: vultures, crows, shrimp
Herbivores- eat ONLY plants; examples: cows, elephants, giraffes, zebras
Carnivores- eat ONLY meat (animals); examples: lions, tigers,sharks, killer whales, seals
Omnivores- eat both plants and other animals; examples: bears, humans, racoons, wasps
Decomposers- absorb dead material and break it down into simple nutrients or fertilizers; examples: bacteria, mushrooms, earthworms, dung beetle

10. Heterotrophic Organisms

11. C) Transfer of Energy
When a zebra eats the grass, it does not obtain all of the energy the grass has (much of it is not metabolized- broken down)
When a lion eats a zebra, it does not get all of the energy from the zebra (some of it is lost as heat) 11

12. Energy flows from producers to consumers
The two (2) previous examples of energy transfer show that no organism EVER receives all of the energy from the organism they just ate
10% Law: Only 10% of the energy from one trophic level is transferred to the next level 12

13. What happens to the other 90%?
Used by the organism for growth, movement, homeostasis (maintain a stable internal environment), reproduction
During metabolism, some energy is transformed into heat 13

14. 14

15. 1.) Trophic Levels
Energy moves from one organism to another when it is eaten
Each step in this transfer of energy is known as a trophic level.
The main trophic levels are producers, consumers, and decomposers.
Most ecosystems have only 3-4 trophic levels
Organisms in the lowest trophic level are usually much more abundant than those in the higher trophic levels. 15

16. Example: Trophic Levels16

17. 2.) Ecological Pyramid
An ecological pyramid shows the relationship between consumers and producers at different trophic (energy) levels in an ecosystem
Shows the relative amounts of energy or matter contained at each trophic level
The Pyramid shows which level has the most energy and has the highest number of organisms 17

18. Ecological Pyramid 18

19. 3.) Food Chains
The energy flow from one trophic level to the other can be displayed as a food chain
A food chain is simple, direct, and linear.
It is a single pathway of feeding relationships.
It involves one organism at each trophic level
Primary Consumers – eat autotrophs (producers); herbivores
Secondary Consumers – eat the primary consumers
Tertiary Consumers – eat the secondary consumers
Decomposers – bacteria and fungi that break down dead organisms and recycle the material back into the environment 19

20. 20

21. 4.) Food Web Most organisms eat more than JUST one organism
When more organisms are involved it is known as a FOOD WEB (shows all of the feeding relationships within an ecosystem)
Food webs are more complex and involve lots of organisms 21

22. The arrow points to the organism that RECEIVES the energy.
Notice the direction the arrow points  the arrow points in the direction of the energy transfer, NOT “what ate what”
The arrow points to the organism that RECEIVES the energy. 22

23. 23

24. D) Species are Connected to Ecosystems
Biodiversity affects the stability of ecosystems
Humans depend on healthy ecosystems to ensure a healthy planet that has balanced cycles.
“Everything depends upon everything”.
When one species disappears, the entire ecosystem is affected. Food chains and symbiotic relationships are affected.
Some species are so critical to the functioning of an ecosystem that they are called keystone species.

25. The Sea Otter Sea otters eat sea urchins.
In the 18oos, sea otters were hunted for their fur to near extinction in the Pacific Northwest.
The sea urchin pop rose and began to eat all of the kelp in the area. With no kelp many other species started to die from starvation.
In 1937, a small group of surviving sea otters were found and protected.
They were reintroduced to the area.
The kelp beds regenerated as the otters ate the sea urchins.