Flow of energy in an ecosystem
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Energy flows in one direction
Source  autotroph  heterotroph
Feeding Relationships
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Food Chain –a series of steps by organisms
transfer energy by eating and being eaten
Feeding Relationships
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Food Webs – feeding relationships
form a network of complex
interactions
Links all food chains in an
ecosystem together
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Each step in the food chain or food web
is called a trophic level
“troph” – feeding, to feed
Pyramids
Relationship of Matter & Energy
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Ecological pyramids- show the relative amounts of matter
& energy contained within each trophic level
Energy Pyramid
Energy Pyramid – shows amount of energy avialable at each
trophic level
--- Only about 10% of the energy from one trophic level is passed
on to the next level
(the rest is given of as heat)
Energy
Pyramid
Biomass Pyramid

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The total amount of living tissue within a
given trophic level (dry mass)
Expressed in g/unit of area
Pyramid of Numbers
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Shows the number of individual organisms at each trophic
level
May be shaped like an inverted pyramid
– Ex: forest ecosystem