Energy Flow in
an Ecosystem
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Energy Flow
• Energy in an ecosystem originally
comes from the sun
• Energy flows through Ecosystems
from producers to consumers
– Producers (make food)
– Consumers (use food by eating
producers or other consumers)
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Producers
• Sunlight is the main
source of energy
for most life on
earth.
• Producers contain
chlorophyll & can
use energy directly
from the sun
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Autotrophs
• An Autotroph is any organism
that can produce its own food
supply!
• Autotrophs are also called
Producers
• Plants, algae, some protists, &
some bacteria are examples
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Niche of a Producer
• Captures energy and transforms
it into organic, stored energy for
the use of living organisms.
• May be photoautotrophs using
light energy (e.g. plants)
• May be chemoautotrophs using
chemical energy (e.g.
cyanobacteria)
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Photoautotroph
Producer That Captures Energy
from the sun by:
– Photosynthesis
• Adds Oxygen to the
atmosphere
• Removes Carbon Dioxide from
the Atmosphere
Algae
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Habitat of Photoautotrophs
• On Land
– Plants
• In The Sea
– Algae
• Tidal Flats & Salt Marshes
– Cyanobacteria
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Chemoautotrophs
• Capture energy from
the bonds of inorganic
molecules such as
Hydrogen Sulfide
• Process is called
Chemosynthesis
• Often occurs in deep
sea vents or gut of
animals
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Called a Black
smoker (thermal
vent)
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Tube Worms living in Black
Smoker
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Consumers
Heterotrophs eat other
organisms to obtain
energy. (e.g. animals)
• Herbivores
– Eat Only Plants
• Carnivores
– Eat Only Other Animals
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Consumers
Heterotrophs eat other organisms
to obtain energy.
• Omnivores (Humans)
– Eat Plants & Animals
• Detritivores (Scavengers)
– Feed On Dead Plant & Animal
Remains (buzzards)
• Decomposers
– Fungi & Bacteria
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Feeding Relationships
Energy flows
through an
ecosystem in
one direction
from producers
to various
levels of
consumers
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Feeding Relationships
• Food Chain
– Simple Energy path through an
ecosystem
• Food Web
– More realistic path through an
ecosystem made of many food
chains
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Food Chain
1st
order
Consumer
2nd Order
Consumer
3rd
Order
consumer
4th Order
Consumer
Producer (trapped
sunlight & stored food)
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Name the Producer, Consumers
& Decomposers in this food
chain:
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Food Web
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Trophic Levels
Each Level In A Food Chain or Food
Web is a Trophic Level.
• Producers
– Always The First Trophic Level
– How Energy Enters The System
• Herbivores
– Second Trophic Level
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Trophic Levels
• Carnivores/Omnivores
– Make Up The Remaining
Trophic Levels
Each level depends on the
one below it for energy.
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Ecological Pyramids
Graphic Representations Of The
Relative Amounts of Energy or
Matter At Each Trophic Level
May be:
Energy Pyramid
Biomass Pyramid
Pyramid of Numbers
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Energy Pyramid
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Biomass Pyramid
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Pyramid of Numbers
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