Food Chains, Webs, &
Pyramids
How Energy Flows in an
Ecosystem
Producers, Consumers, and…
FOOD CHAINS
Producers
• A group of organisms that produce their
own food using sunlight to convert water
& CO2 into glucose (food)
– Also called autotrophs
– Examples: plants & algae
Producers/Autotrophs
Consumers
• Organisms that consume other organisms
in order to live
– Also called heterotrophs because they cannot
make their own food
– Examples: sharks, mushrooms, seals, cows
Consumers/Heterotrophs
Primary Consumers
• Eat plants
– Examples: giraffes, rabbits
Primary Consumers
Secondary Consumers
• Eat primary consumers (eat plant eaters)
– Examples: lions, tigers, bears (oh my!)
Secondary Consumers
Tertiary Consumers
• Eat secondary consumers (eats meat
eaters)
– Examples: cougars, bears, wolves
– Not always present in the food chain
Tertiary Consumers
Scavengers
• Feed on the tissue of dead organisms
(both plants and animals)
– Examples: crows, vultures, shrimp
Scavengers
Decomposers
• Absorb any dead material and break it
down into simple nutrients or fertilizers
– Examples: bacteria & mushrooms
Decomposers
Food Chain
• A diagram that shows how energy in food
flows from one organism to another
– Arrow points toward whichever organism is
receiving the energy
Food Chain
Links in the Chain
• Every organism depends on the other
organisms
– Example: If all of the grass died, the
grasshopper would starve to death causing
the snake and the hawk to starve to death
until eventually even the fungi do not have
anything to feed on
Chains + Chains =
FOOD WEBS
Food Webs
• A diagram that shows the feeding
relationships between organisms in an
ecosystem
– Multiple relationships composed of multiple
food chains
– Most organisms eat more than one organism
– Much more complex and accurate
Food Web
How energy flows…
ENERGY PYRAMIDS
Energy Pyramid
• A triangular diagram that shows an ecosystem’s
loss of energy
– Results as energy passes through the
ecosystem’s food chain/web
– Shows the number of organisms and amount
of matter/energy available at each level
– Decreases at each level because most energy
is lost as heat waste
The End!