Transcript Energy in an Ecosystem

Energy in an
Ecosystem
Chapter 8-3
An Ecosystem’s Energy Source
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Heterotrophs—an organism that cannot make its
own food. (Animals and Fungi)
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Autotrophs – an organism that makes its own
food. (All plants including grasses)
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Heterotrophs are dependent on autotrophs for
food, either directly or indirectly.
An Ecosystem’s Energy Source –
Sunlight and Food Energy
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Energy enters most ecosystems from sunlight
Most autotrophs make their own food through
photosynthesis.
Photosynthesis – the process by which plants
algae, and certain microorganisms convert the
energy in sunlight to energy stored in plants.
An Ecosystem’s Energy SourceSunlight and Food Energy
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With sunlight, plants produce molecules in
which energy is stored.
Plants use the stored energy to grow and carry
out other life processes.
Animals and other heterotrophs eat plants, they
also use the energy stored in plants during
photosynthesis.
Energy Roles in Ecosystems
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Ecologist classify organisms by their role in the
flow of energy through ecosystems.
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Ecologist use the terms producer, consumer and
decomposer to describe energy roles.
Energy Roles in EcosystemsProducers
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Because Autotrophs produce food and store
energy, they are called producers.
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Producer – An organism that can make its own
food.
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Producers include flowers, grass, seaweed, and
cacti.
Energy Roles in EcosystemsConsumers
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Heterotrophs that obtain food and energy by
eating other organisms are called consumers.
Consumers – An organism that obtains energy by
feeding on other organisms.
Consumers include herbivores (eat only plantscows), carnivores (eat only animals-Cougars), and
omnivores (eat both plant and animals-Bears and
most humans).
Energy Roles in EcosystemsDecomposers
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Some heterotrophs, called decomposers, obtain
energy by breaking down wastes and the remains
of dead organisms.
Decomposers-An organism that breaks down the
large molecules from wastes and the remains of
dead organisms into small molecules and returns
important materials to the soil and water.
Decomposers include mold and some bacteria.
Energy Flow in Food Chains and
Food Webs
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Ecologist use a diagram called a food chain to
show the flow of energy from organism to
organism.
Food Chain –The series of events in which one
organism eats another, resulting in a flow of
energy among the organisms involved.
Energy flows from producers to consumers to
decomposers in an ecosystem. The rest of the
energy is released, often as heat.
Energy Flow in Food Chains
• 1. The cactus is the
producer
• 2. First-level consumers
are consumers that eat
producers-Wood rat-a
herbivore
• 3. Second-level
consumers are
consumers that eat firstlevel consumersWeasel-a carnivore
• 4. Third-level consumers
are consumers that eat
second-level consumersBobcat-a carnivore
Energy Flow in Food Webs
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Many food chains exist in each ecosystem and
some overlap.
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A diagram called a food web shows how many
of the food chains are connected.
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Food Web – The pattern of overlapping food chains in
an ecosystem.
Energy Flow in Food Webs
Cycles in Ecosystems
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Organisms use energy as it moves through an
ecosystem from producer to consumer to
decomposer.
Certain matter that organisms need, such as
water carbon and nitrogen cycle through the
ecosystem as well
When a consumer eats a producer, a transfer of
energy occurs as well as a transfer of matter,
such as carbon molecules.
Cycles in the Ecosystem
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Some cycles in which matter and energy
interact in an ecosystem are the water
cycle, the carbon and oxygen cycles, and
the nitrogen cycle.
Cycles in Ecosystems-The Carbon
and Oxygen Cycles
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The recycling of carbon and oxygen is linked to the
flow of energy in an ecosystem.
Carbon dioxide in the air contains Carbon.
Producers take in carbon dioxide during
photosynthesis. They use the carbon in carbon dioxide
to produce other carbon containing molecules such as
the sugars and starches that are stored in their bodies
Cycles in Ecosystems-Carbon and
Oxygen Cycles
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Carbon dioxide is released as a waste product of
respiration.
Meanwhile, oxygen is also cycling through the
ecosystem.
Producers release oxygen as a result of
photosynthesis.
Most organisms take in oxygen and use it during
respiration
Cycles in Ecosystems
Carbon dioxide is used during photosynthesis. Photosynthesis, in
turn, produces oxygen, which is used in respiration. Respiration
produces carbon dioxide, and the cycle begins again.
Cycles in Ecosystems-The Nitrogen
Cycle
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Air is about 78% nitrogen and most organisms
cannot use nitrogen.
Nitrogen gas is called “free” nitrogen, and not
combined with other elements.
Most organisms can only use nitrogen that is
combined with other elements.
Nitrogen fixation - The process of combining free
nitrogen with other elements
Cycles in Ecosystems-The Nitrogen
Cycle
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Bacteria that live in swellings called nodules on
the roots of some plants perform nitrogen
fixation
Bacteria combine nitrogen with other elements
forming “fixed” nitrogen or nitrogen-containing
compounds
Consumers use this “fixed” nitrogen to build
proteins and other substances.
Nitrogen is also fixed in other ways, such as the
action of lightning on free nitrogen.
Cycles in Ecosystems-The Nitrogen
Cycle
The Decay of Biomass
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The total amount of living matter, and the
remains of dead organisms, in an area is the
area’s biomass.
Biomass – the living and formerly living material
in an ecosystem.
The decay of biomass produces matter in the
form of small molecules. This chemical
breakdown also releases the energy stored in the
chemical compounds in the biomass.
The energy is released in the form of heat.