1. Food Chains
&
Food Webs

2. Energy Roles Energy enters as sunlight
Some organisms capture energy and store it as food energy
Organisms that can make their own food are producers
Are the source of all food in ecosystem
Organisms that obtain energy by feeding on other organisms are consumers

3. Decomposers break down wastes and dead organisms & return raw materials to the ecosystem
Know as nature’s recyclers

4. 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 eaten)
When a lion eats a zebra, it does not get all of the energy from the zebra (much of it is lost as heat)

5. This shows that no organism EVER receives all of the energy from the organism they just ate
Only 10% of the energy from one trophic level is transferred to the next – this is called the 10% law

6. Trophic Levels
Energy moves from one organism to another when the organism is eaten
Each step in this transfer of energy is know as a trophic level
The main trophic levels are producers, consumers, and decomposers

7. - Energy Flow in Ecosystems

8. Food Chains & Food Webs
Food Chain – series of events in which one organism eats another and obtains energy
First organism in the food chain is always a PRODUCER
The second organism in the chain feeds on the producer and is called the PRIMARY CONSUMER
The third organism = SECONDARY CONSUMER
The fourth organism = TERTIARY CONSUMER

10. Food chains only show one path that energy can move, BUT…
Food Web – consists of many overlapping food chains in an ecosystem
Food webs can interconnect in what is called a global food web
Think of it as how we don’t eat the same thing every day, neither do other organisms

13. ENERGY PYRAMIDS
Energy Pyramid shows the amount of energy that moves from one feeding level to another
When an organism in an ecosystem eats, it obtains energy
The organism uses some of the energy to move, grow, etc…
This means only SOME of the energy is available for the next organism in the food web

14. The other 90% of the energy is used or lost
Only about 10% of the energy at one level of the food web is transferred to the next highest level
The other 90% of the energy is used or lost
As you move up the pyramid, each level has less energy available than the level below
Most energy is available at the producer level of the pyramid.

15. Since so much energy is lost at each level, the amount of energy available at the producer level limits the number of consumers that an ecosystem can support
SO…usually there are fewer organisms at highest levels of the food web

17. 100J
1,000J
10,000J
100,000J