223_M3_EnergyFlowThroughEcosystems.pptx

• Strategies for Acquiring Energy
• Productivity within Trophic Levels
• Transferring of Energy between Trophic Levels
• Ecological Pyramids
• Biological Magnification
Energy Flow through Ecosystems
Ecosystems > Energy Flow through Ecosystems
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• Food webs illustrate how energy flows through ecosystems, including how
efficiently organisms acquire and use it.
• Autotrophs, producers in food webs, can be photosynthetic or chemosynthetic.
• Photoautotrophs use light energy to synthesize their own food, while
chemoautotrophs use inorganic molecules.
• Chemoautotrophs are usually bacteria that live in ecosystems where sunlight is
unavailable.
• Heterotrophs cannot synthesize their own energy, but must obtain it from
autotrophs or other heterotrophs; they act as consumers in food webs.
Strategies for Acquiring Energy
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Chemoautotrophs
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• A biomass is the total mass of living and previously-living organisms within a
trophic level; ecosystems have characteristic amounts of biomass at each trophic
level.
• The productivity of the primary producers (gross primary productivity) is important
to ecosystems because these organisms bring energy to other living organisms.
• Net primary productivity (energy that remains in the primary producers after
accounting for respiration and heat loss) is available to the primary consumers at
the next trophic level.
Productivity within Trophic Levels
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Energy flow in Silver Springs

• Energy decreases as it moves up trophic levels because energy is lost as
metabolic heat when the organisms from one trophic level are consumed by
organisms from the next level.
• Trophic level transfer efficiency (TLTE) measures the amount of energy that is
transferred between trophic levels.
• A food chain can usually sustain no more than six energy transfers before all the
energy is used up.
• Net production efficiency (NPE) measures how efficiently each trophic level uses
and incorporates the energy from its food into biomass to fuel the next trophic
level.
• Endotherms have a low NPE and use more energy for heat and respiration than
ectotherms, so most endotherms have to eat more often than ectotherms to get
the energy they need for survival.
• Since cattle and other livestock have low NPEs, it is more costly to produce
energy content in the form of meat and other animal products than in the form of
corn, soybeans, and other crops.
Transferring of Energy between Trophic Levels
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Food web of Lake Ontario

• Pyramids of numbers can be either upright or inverted, depending on the
ecosystem.
• Pyramids of biomass measure the amount of energy converted into living tissue at
the different trophic levels.
• The English Channel ecosystem exhibits an inverted biomass pyramid since the
primary producers make up less biomass than the primary consumers.
• Pyramid ecosystem modeling can also be used to show energy flow through the
trophic levels; pyramids of energy are always upright since energy decreases at
each trophic level.
• All types of ecological pyramids are useful for characterizing ecosystem structure;
however, in the study of energy flow through the ecosystem, pyramids of energy
are the most consistent and representative models of ecosystem structure.
Ecological Pyramids
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Ecological pyramids

• Biomagnification increases the concentration of toxic substances in organisms at
higher trophic levels.
• DDT is an example of a substance that biomagnifies; birds accumulate sufficient
amounts of DDT from eating fish to cause adverse effects on bird populations.
• The presence of polychlorinated biphenyls (PCB) in phytoplankton causes
increased PCB concentrations in walleyes and birds.
• Heavy metals, such as mercury and cadmium, found in certain types of seafood
can also biomagnify.
Biological Magnification
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PCB concentration in Lake Huron

Appendix

Key terms
• apex consumer consumers with few to no predators of their own, residing at the top of their food chain
• assimilation the biomass of the present trophic level after accounting for the energy lost due to incomplete ingestion of food,
energy used for respiration, and energy lost as waste
• biomagnification the process, in an ecosystem, in which a higher concentration of a substance in an organism is obtained
higher up the food chain
• biomass the total mass of all living things within a specific area, habitat, etc.
• chemoautotroph a simple organism, such as a protozoan, that derives its energy from chemical processes rather than
photosynthesis
• dichlorodiphenyltrichloroethane a chlorinated hydrocarbon which is mainly used as an insecticide (DDT)
• ecological pyramid diagram that shows the relative amounts of energy or matter or numbers of organisms within each trophic
level in a food chain or food web
• gross primary productivity rate at which photosynthetic primary producers incorporate energy from the sun
• heterotroph an organism that requires an external supply of energy in the form of food, as it cannot synthesize its own
• net consumer productivity energy content available to the organisms of the next trophic level
• net primary productivity energy that remains in the primary producers after accounting for the organisms' respiration and heat
loss
• net production efficiency (NPE) measure of the ability of a trophic level to convert the energy it receives from the previous
trophic level into biomass
Ecosystems

• photoautotroph an organism that can synthesize its own food by using light as a source of energy
• trophic level a particular position occupied by a group of organisms in a food chain (primary producer, primary consumer,
secondary consumer, or tertiary consumer)
• trophic level transfer efficiency (TLTE) energy transfer efficiency between two successive trophic levels
Ecosystems

PCB concentration in Lake Huron
This chart shows the PCB concentrations found at the various trophic levels in the Saginaw Bay ecosystem of Lake Huron. Numbers on the x-axis reflect
enrichment with heavy isotopes of nitrogen (15N), which is a marker for increasing trophic levels. Notice that the fish in the higher trophic levels
accumulate more PCBs than those in lower trophic levels.
Connexions. CC BY 3.0 http://cnx.org/content/m44887/latest/Figure_46_02_03.jpg View on Boundless.com
Ecosystems

Food web of Lake Ontario
This food web shows the interactions between organisms across trophic levels in the Lake Ontario ecosystem. Primary producers are outlined in green,
primary consumers in orange, secondary consumers in blue, and tertiary (apex) consumers in purple. Arrows point from an organism that is consumed
to the organism that consumes it. Notice how some lines point to more than one trophic level. For example, the opossum shrimp eats both primary
producers and primary consumers.
Connexions. "Ecology of Ecosystems." CC BY 3.0 http://cnx.org/content/m44885/latest/#fig-ch46_01_05 View on Boundless.com
Ecosystems

Energy flow in Silver Springs
This conceptual model shows the flow of energy through a spring ecosystem in Silver Springs, Florida. Notice that the energy decreases with each
increase in trophic level.
Connexions. "Ecology of Ecosystems." CC BY 3.0 http://cnx.org/content/m44885/latest/#fig-ch46_01_07 View on Boundless.com
Ecosystems

Ecological pyramids
Ecological pyramids depict the (a) biomass, (b) number of organisms, and (c) energy in each trophic level.
Connexions. CC BY 3.0 http://cnx.org/content/m44887/latest/Figure_46_02_02.png View on Boundless.com
Ecosystems

Chemoautotrophs
Swimming shrimp, a few squat lobsters, and hundreds of vent mussels are seen at a hydrothermal vent at the bottom of the ocean. As no sunlight
penetrates to this depth, the ecosystem is supported by chemoautotrophic bacteria and organic material that sinks from the ocean's surface.
Connexions. CC BY 3.0 http://cnx.org/content/m44887/latest/Figure_46_02_01.jpg View on Boundless.com
Ecosystems

Ecosystems
Organisms that can make their own food using inorganic
molecules are called _____, while organisms that make their own
food using light energy are called _____.
A) photoautotrophs; chemoautotrophs
B) chemoautotrophs; photoautotrophs
C) heterotrophs; photoautotrophs
D) heterotrophs; chemoautotrophs

Boundless - LO. "Boundless." CC BY-SA 3.0 http://www.boundless.com/
Ecosystems
Organisms that can make their own food using inorganic
molecules are called _____, while organisms that make their own
food using light energy are called _____.
A) photoautotrophs; chemoautotrophs
B) chemoautotrophs; photoautotrophs
C) heterotrophs; photoautotrophs
D) heterotrophs; chemoautotrophs

Ecosystems
The rate at which photosynthetic primary producers incorporate
solar energy is referred to as ______, while the energy that
remains in the primary producers following respiration and heat
loss is referred to as ______.
A) biomass; gross primary productivity
B) gross primary productivity; net primary productivity
C) net primary productivity; gross primary productivity
D) photoautotrophy; chemoautotrophy

Ecosystems
Fill in the blank. Ecological/trophic pyramids are a good way to
illustrate energy needs in an ecosystem. This is because the
energy is ______ as it passes from one trophic level to the next.
A) gained
B) constant
C) lost
D) gained and then lost

Saylor OER. "BIO102: Introduction to Evolutionary Biology and Ecology « Saylor.org – Free Online Courses Built by Professors." CC BY 3.0
http://www.saylor.org/courses/bio102/
Ecosystems
Fill in the blank. Ecological/trophic pyramids are a good way to
illustrate energy needs in an ecosystem. This is because the
energy is ______ as it passes from one trophic level to the next.
A) gained
B) constant
C) lost
D) gained and then lost

Ecosystems
Which of the following about the energy transfer between trophic
levels is true?
A) There is an infinite number of energy transfers within a food chain.
B) Ectotherms utilize energy more efficiently than endotherms.
C) Endotherms utilize energy more efficiently than ectotherms.
D) Energy can only be transferred once within a food chain.

Ecosystems
Why do grasslands typically exhibit an upright pyramid shape
during the summer?
A) There are more primary consumers than primary producers.
B) There are more primary producers than primary consumers.
C) Organisms at the top of the pyramid are subject to greater predation.
D) The number of organisms increases at each trophic level.

Ecosystems
The English Channel ecosystem has an inverted shape because
the ______.
A) primary producers have a high turnover rate
B) primary producers have a low turnover rate
C) primary consumers have a high turnover rate
D) lack of productivity of primary producers

OpenStax OER. "Energy Flow through Ecosystems." CC BY 3.0 http://cnx.org/content/m44887/latest/?collection=col11448/latest
Ecosystems
The English Channel ecosystem has an inverted shape because
the ______.
A) primary producers have a high turnover rate
B) primary producers have a low turnover rate
C) primary consumers have a high turnover rate
D) lack of productivity of primary producers

Ecosystems
Which of the following is a result of biomagnification?
A) organisms at the lowest trophic levels are unaffected by toxic
substances
B) organisms at the highest trophic levels accumulate the greatest
amount of toxic substances
C) toxic substances are brought through the ecosystem by the apex
consumers
D) all of these answers

Attribution
• Connexions. "Energy Flow through Ecosystems." CC BY 3.0 http://cnx.org/content/m44887/latest/?collection=col11448/latest
• Wikipedia. "Heterotroph." CC BY-SA 3.0 http://en.wikipedia.org/wiki/Heterotroph
• Wiktionary. "heterotroph." CC BY-SA 3.0 http://en.wiktionary.org/wiki/heterotroph
• Wiktionary. "photoautotroph." CC BY-SA 3.0 http://en.wiktionary.org/wiki/photoautotroph
• Wiktionary. "chemoautotroph." CC BY-SA 3.0 http://en.wiktionary.org/wiki/chemoautotroph
• Wiktionary. "trophic level." CC BY-SA 3.0 http://en.wiktionary.org/wiki/trophic+level
• Boundless Learning. "Boundless." CC BY-SA 3.0 http://www.boundless.com//biology/definition/net-primary-productivity
• Boundless Learning. "Boundless." CC BY-SA 3.0 http://www.boundless.com//biology/definition/gross-primary-productivity
• Wiktionary. "biomass." CC BY-SA 3.0 http://en.wiktionary.org/wiki/biomass
• Wiktionary. "assimilation." CC BY-SA 3.0 http://en.wiktionary.org/wiki/assimilation
• Boundless Learning. "Boundless." CC BY-SA 3.0 http://www.boundless.com//biology/definition/net-consumer-productivity
• Boundless Learning. "Boundless." CC BY-SA 3.0 http://www.boundless.com//biology/definition/net-production-efficiency-npe
• Boundless Learning. "Boundless." CC BY-SA 3.0 http://www.boundless.com//biology/definition/trophic-level-transfer-efficiency-
tlte
Ecosystems

• Wiktionary. "ecological pyramid." CC BY-SA 3.0 http://en.wiktionary.org/wiki/ecological+pyramid
• Boundless Learning. "Boundless." CC BY-SA 3.0 http://www.boundless.com//biology/definition/apex-consumer
• Wiktionary. "dichlorodiphenyltrichloroethane." CC BY-SA 3.0 http://en.wiktionary.org/wiki/dichlorodiphenyltrichloroethane
• Wiktionary. "biomagnification." CC BY-SA 3.0 http://en.wiktionary.org/wiki/biomagnification
Ecosystems

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