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Science 7
Unit A: Interactions and Ecosystems
2.2 Food Chains Demonstrate the Flow of Energy in Ecosystems
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Food and energy in an ecosystem flow from the producers to the
consumers
Food chain: a convenient way to show how energy moves among living
things in an ecosystem
o Always starts with a producer (ex. Plant)
o A primary consumer eats the producer (ex. Herbivore)
o Secondary consumers eat primary consumers (ex. Carnivore)
Energy Flow in Ecosystems
 Most ecosystems on Earth get their energy from the Sun
o Through photosynthesis producers make the Sun’s energy available
to producers in the form of glucose
o This is what makes producers essential to ecosystems!
 Usually way more producers in an ecosystem than consumers
2.2 Food Chains Demonstrate the Flow of Energy in Ecosystems
Hills 2014
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Producers convert Sun’s energy into the chemical energy of glucose
o The producers uses 90% of the glucose it makes for life functions
(ex. growing)
o 10% is stored as nutrients in a specific part of the plant (ex. In
the roots for carrots)
 Only 10% of the plant’s energy is available to the herbivore
o Herbivores use 90% of the glucose they get from producers for
life functions (ex. Body heat)
 10% is stored for the carnivore to consume
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Energy is not recycled in an ecosystem
o It follows a one-way path
o Therefore producers depend on a constant supply of energy from
the Sun
o Matter is recycled
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2.2 Food Chains Demonstrate the Flow of Energy in Ecosystems

Hills 2014
Producers depend on sunlight
o Primary consumers depend on producers
o Secondary consumers depend on primary consumers
o Decomposers and scavengers depend on everybody
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