Food Chains�Food Webs�Energy Pyramids
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Food Chain
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A food chain is a simple model (diagram) of the feeding relationships and energy transfer in an ecosystem.
The movement of energy through an ecosystem can be shown in diagrams called food chains.
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Trophic Levels
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Trophic levels (feeding levels) are the “steps” in a food chain, moving from producers to the different levels of consumers.
Food Chain
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The first organism in a food chain is always a producer. They make their own food.
The primary consumer is the 1st level of consumers. They are usually herbivores.
The secondary consumer is the 2nd level of consumers. They are usually carnivores or omnivores.
The tertiary consumer is the 3rd level of consumers. Usually carnivores.
The quaternary consumer is the 4th level of consumers. Usually carnivores.
Terrestrial and Land Food Chains
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Terrestrial (Land) Food Chain
Marine (Ocean) Food Chain
In which direction is the energy moving (up or down)?
Mountain Food Chain
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For example, shrubs are food for deer, and deer are food for mountain lions.
Shrubs are the beginning of the food chain. They use sunlight to perform photosynthesis, making them producers.
The deer is the first consumer of the food chain; it eats the shrub. It is the primary consumer.
The mountain lion is the second consumer of the food chain. It eats the deer. It is the secondary consumer.
Pond Food Chain with 6 trophic levels
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Algae
Mosquito larvae
Dragonfly larvae
Perch
Pike
Human
Creating a Food Chain
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Next
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Create a food chain from this ecosystem.
Phytoplankton (algae)
bass
snapping turtle
A Food Web is a network of many food chains that shows how energy is transferred within an entire ecosystem
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The arrows point in the direction in which the energy (the food) is moving.
Lake Ecosystem
On your worksheet, label the Producers in this food web with a P, label the Primary Consumers with PC, label Secondary Consumers SC, label Quaternary Consumers with QC.
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Lake Ecosystem
We can show the relationships between populations in an ecosystem with the help of a Food Web
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What would happen in this ecosystem if chemicals poisoned many of the hawks?
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There will be nothing to eat the snakes, so their numbers will increase.
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All the frogs get eaten
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More crickets
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No frogs.
Most of the cattail gets eaten by the crickets
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The number of crickets increases, so the number of shrews goes up as well.
Now the crickets don’t have enough food so their numbers go down. Plus, the shrews are eating up the crickets.
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..and so on. The numbers of each species have an effect on the numbers of the other species in the web.
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Predict What Will Happen
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Use the food web worksheet to predict what might happen in the following situations:
A) There is very little rain and much of the Marsh Grass and Cattail die off.
B) Humans nearby bring cats into the area (cats eat shrews & frogs).
Trophic Levels
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Diagram that shows the amount of energy available at each trophic level of an ecosystem
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The Trophic level is the position the organism holds in a food chain.
Examples: Producer, Primary Consumer, Secondary Consumer, Tertiary Consumer, Quaternary Consumer
Trophic Levels
Energy Pyramid�diagram that shows the amount of energy available at each trophic level in an ecosystem
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What do you notice happening as you go from the bottom to the top of the energy pyramid?
Energy Pyramid�
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Organisms get larger (biomass increases)
Number of organisms decreases
Only About 10% of the Energy in Organisms of One Trophic Level Is Captured by Organisms of the Next Level
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What do you think happened to the rest of the energy?
It got used while the organism was alive. It takes energy to live! An organism uses energy to:
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Some was lost as waste (pee, poop, sweat)
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Ocean Food Chain
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large fish