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
4
Niche of a Producer
• Captures energy and transforms it
into organic, stored energy for the
use of living organisms.
• May be photo-autotrophs using light
energy (e.g. plants)
• May be chemo-autotrophs 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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Photosynthesis –
6CO2 + 6H2O + chlorophyll  C6H12O6 + 6O2
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6O2 + C6H12O6 ---> 6H2O + 6CO2 + energy
CELLULAR
RESPIRATION is
the chemical
reaction that
releases the
energy (ATP) in
glucose.
Cellular respiration reactions
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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
Called a Black
smoker (thermal
vent)
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Tube Worms living in Black
Smoker
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Some energy in the primary
consumer is STORED & not
lost to the atmosphere or
used by the consumer itself.
This energy is available for
another consumer (predator).
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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
Feeding Relationships
Energy flows
through an
ecosystem in
one direction
from producers
to various
levels of
consumers
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The transfer of energy from
the sun to producer to primary
consumer then to higher order
consumers can be shown in a
FOOD CHAIN.
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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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• An energy pyramid follows the 10% rule – only 10% of the
energy available at one trophic level is transferred to the
next trophic level.
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Trophic levels- 10% rule
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Pyramid of Numbers
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Identify the Producers, Consumers, &
Decomposers:
Count
the Food
Chains!
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Carbon Cycle
• All living things are made of carbon. Carbon is also a part
of the ocean, air, and even rocks. Because the Earth is a
dynamic place, carbon does not stay still. It is on the
move!
• Carbon dioxide is a greenhouse gas and traps heat in the
atmosphere. Without it and other greenhouse gases, Earth
would be a frozen world. But humans have burned so
much fuel that there is about 30% more carbon dioxide in
the air today than there was about 150 years ago, and
Earth is becoming a warmer place.
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Nitrogen fixation
• Three processes are responsible for most of
the nitrogen fixation in the biosphere:
– atmospheric fixation by lightning
– biological fixation by certain microbes —
alone or in a symbiotic relationship with
some plants and animals
– industrial fixation
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What are some ways that humans disturb
ecosystems?
• Humans upset the homeostasis of
ecosystems
– Monoculture
– destruction of habitats
– biocides – bioaccumulation
– pollution – (acid rain)
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Why is biodiversity so important?
• More healthy ecosystems with more links
• Preservation of genetic diversity – ensures
survival
• Some plants are providing medicines that
are very useful
• Chance to learn about many different
species is lost
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What are we doing to preserve our natural areas?
• Establishing wilderness areas – no engines allowed
• Replanting deforested areas
• Establishing breeding population, reintroducing
species, relocating
• Genetic diversity preserved in freezers!
• Crossing species
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Resources
• fig.cox.miami.edu/Faculty/Dana/105F00_13.html
• http://www.factmonster.com/images/photosynthesi
s.gif
• www.eo.ucar.edu/kids/green/cycles6.htm
• http://users.rcn.com/jkimball.ma.ultranet/BiologyPa
ges/N/NitrogenCycle.html
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