4.2 Energy flow

Description

Nature of science:
Use theories to explain natural phenomena—the concept of energy flow explains the limited length of food chains. (2.2)

Understandings:

Most ecosystems rely on a supply of energy from sunlight.
Light energy is converted to chemical energy in carbon compounds by photosynthesis.
Chemical energy in carbon compounds flows through food chains by means of feeding.
Energy released from carbon compounds by respiration is used in living organisms and converted to heat.
Living organisms cannot convert heat to other forms of energy.
Heat is lost from ecosystems.
Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels.

Applications and skills:

Skill: Quantitative representations of energy flow using pyramids of energy.

Guidance:

Pyramids of number and biomass are not required. Students should be clear that biomass in terrestrial ecosystems diminishes with energy along food chains due to loss of carbon dioxide, water and other waste products, such as urea.
Pyramids of energy should be drawn to scale and should be stepped, not triangular. The terms producer, first consumer and second consumer and so on should be used, rather than first trophic level, second trophic level and so on.
The distinction between energy flow in ecosystems and cycling of inorganic nutrients should be stressed. Students should understand that there is a continuous but variable supply of energy in the form of sunlight but that the supply of nutrients in an ecosystem is finite and limited.

International-mindedness:

The energetics of food chains is a factor in the efficiency of food production for the alleviation of world hunger.

Utilization:
Syllabus and cross-curricular links:
Biology
Topic 2.8 Cell respiration
Topic 2.9 Photosynthesis
Physics
Topic 2.3 Work, energy and power
Topic B.2 Thermodynamics
Environmental systems and societies
Topic 2.3 Flows of energy and matter

Directly related questions

21N.2.HL.TZ0.1d:
Suggest reasons for the decreases in biomass of autotrophs as temperature rises, despite the increases in photosynthesis.
17N.2.SL.TZ0.04b: Outline why the number of trophic levels is limited in a food chain.
17N.2.SL.TZ0.04b: Outline why the number of trophic levels is limited in a food chain.
17N.2.SL.TZ0.b: Outline why the number of trophic levels is limited in a food chain.
21N.1.SL.TZ0.18: In a woodland ecosystem, each tree provides food for numerous aphids which feed on the sap of the...
21M.2.SL.TZ2.4d.i:
Deduce whether jellyfish or crustacea are a richer source of carbon in a food chain.
21M.2.SL.TZ2.4d.i:
Deduce whether jellyfish or crustacea are a richer source of carbon in a food chain.
21M.2.SL.TZ2.d.i:
Deduce whether jellyfish or crustacea are a richer source of carbon in a food chain.
21M.2.SL.TZ2.4d.ii:
Suggest with a reason whether having a large body mass is an advantage or disadvantage for jellyfish.
21M.2.SL.TZ2.4d.ii:
Suggest with a reason whether having a large body mass is an advantage or disadvantage for jellyfish.
21M.2.SL.TZ2.d.ii:
Suggest with a reason whether having a large body mass is an advantage or disadvantage for jellyfish.
21N.2.HL.TZ0.1d:
Suggest reasons for the decreases in biomass of autotrophs as temperature rises, despite the increases in photosynthesis.
21N.2.SL.TZ0.3b.ii:
Explain the reasons for food chains rarely containing more than four or five trophic levels.
21N.1.SL.TZ0.18: In a woodland ecosystem, each tree provides food for numerous aphids which feed on the sap of the...
21N.2.HL.TZ0.d:
Suggest reasons for the decreases in biomass of autotrophs as temperature rises, despite the increases in photosynthesis.
18M.2.SL.TZ2.3c: Explain how energy and nutrients are transferred in ecosystems.
22M.2.SL.TZ2.7a:
Outline energy flow through a community in a natural ecosystem.
21N.2.SL.TZ0.3b.ii:
Explain the reasons for food chains rarely containing more than four or five trophic levels.
21N.2.SL.TZ0.b.ii:
Explain the reasons for food chains rarely containing more than four or five trophic levels.
18N.1.SL.TZ0.17: The diagram shows interactions between food chains in an ecosystem in the African...
18N.1.SL.TZ0.17: The diagram shows interactions between food chains in an ecosystem in the African...
18M.2.SL.TZ2.3c: Explain how energy and nutrients are transferred in ecosystems.
19M.1.SL.TZ2.18:
The Silver Springs feed into the Silver River in Florida. The diagram shows a pyramid of energy for the Silver Springs ecosystem. The units are kJ m^–2 y^–1.

[Source: © International Baccalaureate Organization 2019]

What do level I and level III represent in the pyramid of energy?
22M.2.SL.TZ2.7a:
Outline energy flow through a community in a natural ecosystem.
22M.2.SL.TZ2.a:
Outline energy flow through a community in a natural ecosystem.
18M.2.SL.TZ2.c: Explain how energy and nutrients are transferred in ecosystems.
19M.1.SL.TZ1.18:
The diagram shows the food web for an aquatic ecosystem in which letters R–Z represent individual species.

[Source: © International Baccalaureate Organization 2019]

Which organism is a tertiary consumer?

A. Organism T

B. Organism U

C. Organism W

D. Organism Y
19M.1.SL.TZ2.18:
The Silver Springs feed into the Silver River in Florida. The diagram shows a pyramid of energy for the Silver Springs ecosystem. The units are kJ m^–2 y^–1.

[Source: © International Baccalaureate Organization 2019]

What do level I and level III represent in the pyramid of energy?
19N.2.SL.TZ0.5c: Explain the movement of energy and inorganic nutrients in an ecosystem.
19N.2.SL.TZ0.5c: Explain the movement of energy and inorganic nutrients in an ecosystem.
19N.2.SL.TZ0.c: Explain the movement of energy and inorganic nutrients in an ecosystem.
18M.1.SL.TZ1.17: Animals in the highest trophic level of a food chain will often be the largest in body size but...
18M.1.SL.TZ1.17: Animals in the highest trophic level of a food chain will often be the largest in body size but...
18M.2.HL.TZ2.6c: Describe the reasons for the shape of a pyramid of energy.
18M.2.HL.TZ2.6c: Describe the reasons for the shape of a pyramid of energy.
18M.2.HL.TZ2.c: Describe the reasons for the shape of a pyramid of energy.
18M.1.HL.TZ2.22: Which processes occur in an ecosystem? I. Biomass increases in each successive trophic...
19M.1.SL.TZ1.18:
The diagram shows the food web for an aquatic ecosystem in which letters R–Z represent individual species.

[Source: © International Baccalaureate Organization 2019]

Which organism is a tertiary consumer?

A. Organism T

B. Organism U

C. Organism W

D. Organism Y
18M.1.HL.TZ2.22: Which processes occur in an ecosystem? I. Biomass increases in each successive trophic...
19M.1.HL.TZ1.14:
The diagram shows the food web for an aquatic ecosystem in which letters R–Z represent individual species.

[Source: © International Baccalaureate Organization 2019]

Which organism is a tertiary consumer?

A. Organism T

B. Organism U

C. Organism W

D. Organism Y
19M.2.SL.TZ2.3a.i:
State two causes of the decrease of biomass along food chains in terrestrial ecosystems.
19M.1.HL.TZ1.14:
The diagram shows the food web for an aquatic ecosystem in which letters R–Z represent individual species.

[Source: © International Baccalaureate Organization 2019]

Which organism is a tertiary consumer?

A. Organism T

B. Organism U

C. Organism W

D. Organism Y
19M.2.SL.TZ2.3a.i:
State two causes of the decrease of biomass along food chains in terrestrial ecosystems.
19M.2.SL.TZ2.a.i:
State two causes of the decrease of biomass along food chains in terrestrial ecosystems.
19N.2.HL.TZ0.8c:
Explain the movement of energy and inorganic nutrients in an ecosystem.
19M.2.HL.TZ2.8a: Outline energy flow through a food chain.
19N.2.HL.TZ0.8c:
Explain the movement of energy and inorganic nutrients in an ecosystem.
19M.2.HL.TZ2.8a: Outline energy flow through a food chain.
19M.2.HL.TZ2.a: Outline energy flow through a food chain.
20N.2.HL.TZ0.4a:
Distinguish between the transfers of energy and inorganic nutrients in ecosystems.
20N.2.HL.TZ0.4a:
Distinguish between the transfers of energy and inorganic nutrients in ecosystems.
20N.2.HL.TZ0.a:
Distinguish between the transfers of energy and inorganic nutrients in ecosystems.
19N.2.HL.TZ0.c:
Explain the movement of energy and inorganic nutrients in an ecosystem.
21M.2.SL.TZ2.4c:
Explain how energy enters, flows through and is lost from marine food chains.
21M.1.SL.TZ1.21: The diagram shows the energy flow between five “sinks” in a terrestrial ecosystem. In a...
20N.2.HL.TZ0.8a:
Outline the criteria that should be used to assess whether a group of organisms is a species.
21M.2.SL.TZ2.4c:
Explain how energy enters, flows through and is lost from marine food chains.
20N.2.HL.TZ0.8a:
Outline the criteria that should be used to assess whether a group of organisms is a species.
20N.2.HL.TZ0.a:
Outline the criteria that should be used to assess whether a group of organisms is a species.
21M.1.SL.TZ1.21: The diagram shows the energy flow between five “sinks” in a terrestrial ecosystem. In a...
21M.2.SL.TZ2.c:
Explain how energy enters, flows through and is lost from marine food chains.
21M.1.SL.TZ2.18:
The diagram shows the flow of energy through an ecosystem in ${kJ m}^{- 2} y^{- 1} .$

[Source: “Energy flow: Figure 3,” (https://cnx.org/contents/[email protected]:fbNheNoN@8/Energy-Flow) by OpenStax College, Biology CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/).]

What percentage of the energy passed from primary producers to primary consumers is lost to cellular respiration by tertiary consumers?

A. 0.001%

B. 0.08%

C. 0.2%

D. 0.4%
20N.1.HL.TZ0.16: Plankton are major producers in marine ecosystems. Only a small proportion of the energy...
21M.1.SL.TZ2.18:
The diagram shows the flow of energy through an ecosystem in ${kJ m}^{- 2} y^{- 1} .$

[Source: “Energy flow: Figure 3,” (https://cnx.org/contents/[email protected]:fbNheNoN@8/Energy-Flow) by OpenStax College, Biology CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/).]

What percentage of the energy passed from primary producers to primary consumers is lost to cellular respiration by tertiary consumers?

A. 0.001%

B. 0.08%

C. 0.2%

D. 0.4%
20N.1.HL.TZ0.16: Plankton are major producers in marine ecosystems. Only a small proportion of the energy...
21N.2.SL.TZ0.3b.i:
The image shows an example of a soil food web.

[Source: Anon., n.d. The Soil Food Web. [image online] Available at: https://www.nrcs.usda.gov/wps/portal/nrcs/
photogallery/soils/health/biology/gallery/?cid=1788&position=Promo [Accessed 11 March 2020].]

Draw a food chain from this food web, showing at least three organisms.
22M.1.SL.TZ2.18: The diagram shows part of a food chain. The left box represents producers and the right box...
22M.1.SL.TZ1.18: The table contains information about the diet of some animals. Which pyramid of energy...
22M.1.SL.TZ2.18: The diagram shows part of a food chain. The left box represents producers and the right box...
22M.1.SL.TZ1.18: The table contains information about the diet of some animals. Which pyramid of energy...
21N.2.SL.TZ0.3b.i:
The image shows an example of a soil food web.

[Source: Anon., n.d. The Soil Food Web. [image online] Available at: https://www.nrcs.usda.gov/wps/portal/nrcs/
photogallery/soils/health/biology/gallery/?cid=1788&position=Promo [Accessed 11 March 2020].]

Draw a food chain from this food web, showing at least three organisms.
21N.2.SL.TZ0.b.i:
The image shows an example of a soil food web.

[Source: Anon., n.d. The Soil Food Web. [image online] Available at: https://www.nrcs.usda.gov/wps/portal/nrcs/
photogallery/soils/health/biology/gallery/?cid=1788&position=Promo [Accessed 11 March 2020].]

Draw a food chain from this food web, showing at least three organisms.
21N.2.HL.TZ0.1b:
Compare and contrast the effects of temperature on the biomass of autotrophs and heterotrophs with added nutrients.
22N.2.SL.TZ0.6a:
Outline how energy flows in an ecosystem.
21N.2.HL.TZ0.1b:
Compare and contrast the effects of temperature on the biomass of autotrophs and heterotrophs with added nutrients.
21N.2.HL.TZ0.b:
Compare and contrast the effects of temperature on the biomass of autotrophs and heterotrophs with added nutrients.
22M.2.SL.TZ1.1f: The mean daily food intake fluctuated from day to day. State the month that contains the day on...
22N.2.SL.TZ0.6a:
Outline how energy flows in an ecosystem.
22M.2.SL.TZ1.1f: The mean daily food intake fluctuated from day to day. State the month that contains the day on...
22M.2.SL.TZ1.f: The mean daily food intake fluctuated from day to day. State the month that contains the day on...
22N.2.SL.TZ0.a:
Outline how energy flows in an ecosystem.
23M.3.HL.TZ1.15a: Identify the trophic level of sea lions.
22M.2.SL.TZ1.1g: Outline the relationship between ambient daily temperature and food intake in March.
22M.2.SL.TZ1.1g: Outline the relationship between ambient daily temperature and food intake in March.
22M.2.SL.TZ1.g: Outline the relationship between ambient daily temperature and food intake in March.
23M.3.HL.TZ1.15a: Identify the trophic level of sea lions.
23M.2.HL.TZ2.4ai: State with a reason whether pangolins are autotrophic or heterotrophic.
23M.3.HL.TZ1.a: Identify the trophic level of sea lions.
23M.1.HL.TZ2.15: Which statement applies to transfers in an ecosystem? A. Green plants can transfer heat energy...
23M.2.HL.TZ2.4ai: State with a reason whether pangolins are autotrophic or heterotrophic.
23M.2.HL.TZ2.i: State with a reason whether pangolins are autotrophic or heterotrophic.
23M.2.HL.TZ2.6a:
Explain how changes to the cell cycle can result in tumour formation.
22M.2.SL.TZ1.1h: Suggest, with a reason, how the activity of the sloth varies with ambient temperature.
23M.1.SL.TZ2.19: Which statement applies to transfers in an ecosystem? A. Green plants can transfer heat energy...
23M.1.SL.TZ2.19: Which statement applies to transfers in an ecosystem? A. Green plants can transfer heat energy...
22M.2.SL.TZ1.1h: Suggest, with a reason, how the activity of the sloth varies with ambient temperature.
22M.2.SL.TZ1.h: Suggest, with a reason, how the activity of the sloth varies with ambient temperature.
23M.1.SL.TZ1.20:
Humans have persecuted predators such as coyotes (Canis latrans), causing severe reduction in the number of large carnivores throughout the world. The diagram represents part of a food web in Texas, USA.

_{[Source: Coyote: https://commons.wikimedia.org/wiki/File:2009-Coyote-Yosemite.jpg. CC-BY-SA 3.0; Yathin S. Krishnappa, Jan.}
_{2009, Coyote from Yosemite National Park, California in snow.]}
_{[Source: Fox: https://commons.wikimedia.org/wiki/File:Foxes_of_Island_Beach_State_Park_New_Jersey_(16324545492).jpg.}
_{CC-Attribution 2.0; Anthony Quintano, Jan. 2015, Foxes of Island Beach State Park New Jersey.]}
_{[Source: Rodent/Brown Rat: https://commons.wikimedia.org/wiki/File:Rattus_norvegicus_-_Brown_rat_02.jpg. CC-BY-SA-4.0}
_{Zeynel Cebeci, May 2020; Brown Rat, Adana, Turkey.]}
_{[Source: Lagomorph: https://commons.wikimedia.org/wiki/File:Eastern_Cottontail.JPG. CC 3.0. Taken by Gareth Rasberry,}
_{Huntington Beach State Park, Murrells Inlet, South Carolina, USA.]}
_{[Source: Nest Eggs: https://commons.wikimedia.org/wiki/File:Eastern_Phoebe-nest-Brown-headed-Cowbird-egg.jpg. CC 3.0.}
_{Galawebdesign, June 2007, Eastern Phoebe (Sayornis phoebe) nest with one Brown-headed Cowbird (Molothrus ater)}
_egg.]

What is a possible outcome for the lagomorph population in this ecosystem if coyote numbers were controlled by killing them to reduce losses of domestic livestock?

A. Decrease because there are fewer predators

B. Increase because there are fewer foxes to eat them

C. Decrease because there are more rodents for foxes to eat

D. Increase because, although there are more foxes, there are also more rodents
23M.2.HL.TZ2.6a:
Explain how changes to the cell cycle can result in tumour formation.
23M.2.HL.TZ2.a:
Explain how changes to the cell cycle can result in tumour formation.
23M.1.SL.TZ2.20: The diagram shows the carbon cycle. Which letters represent respiration? A. R and T B. P and...
23M.1.SL.TZ2.20: The diagram shows the carbon cycle. Which letters represent respiration? A. R and T B. P and...
23M.1.HL.TZ2.15: Which statement applies to transfers in an ecosystem? A. Green plants can transfer heat energy...
23M.2.SL.TZ1.7a:
Describe how plants are named and classified, including recognition features of plant phyla.
23M.2.SL.TZ1.7a:
Describe how plants are named and classified, including recognition features of plant phyla.
23M.2.SL.TZ1.a:
Describe how plants are named and classified, including recognition features of plant phyla.
23M.2.SL.TZ2.4ai: State with a reason whether pangolins are autotrophic or heterotrophic.
23M.1.SL.TZ1.20:
Humans have persecuted predators such as coyotes (Canis latrans), causing severe reduction in the number of large carnivores throughout the world. The diagram represents part of a food web in Texas, USA.

_{[Source: Coyote: https://commons.wikimedia.org/wiki/File:2009-Coyote-Yosemite.jpg. CC-BY-SA 3.0; Yathin S. Krishnappa, Jan.}
_{2009, Coyote from Yosemite National Park, California in snow.]}
_{[Source: Fox: https://commons.wikimedia.org/wiki/File:Foxes_of_Island_Beach_State_Park_New_Jersey_(16324545492).jpg.}
_{CC-Attribution 2.0; Anthony Quintano, Jan. 2015, Foxes of Island Beach State Park New Jersey.]}
_{[Source: Rodent/Brown Rat: https://commons.wikimedia.org/wiki/File:Rattus_norvegicus_-_Brown_rat_02.jpg. CC-BY-SA-4.0}
_{Zeynel Cebeci, May 2020; Brown Rat, Adana, Turkey.]}
_{[Source: Lagomorph: https://commons.wikimedia.org/wiki/File:Eastern_Cottontail.JPG. CC 3.0. Taken by Gareth Rasberry,}
_{Huntington Beach State Park, Murrells Inlet, South Carolina, USA.]}
_{[Source: Nest Eggs: https://commons.wikimedia.org/wiki/File:Eastern_Phoebe-nest-Brown-headed-Cowbird-egg.jpg. CC 3.0.}
_{Galawebdesign, June 2007, Eastern Phoebe (Sayornis phoebe) nest with one Brown-headed Cowbird (Molothrus ater)}
_egg.]

What is a possible outcome for the lagomorph population in this ecosystem if coyote numbers were controlled by killing them to reduce losses of domestic livestock?

A. Decrease because there are fewer predators

B. Increase because there are fewer foxes to eat them

C. Decrease because there are more rodents for foxes to eat

D. Increase because, although there are more foxes, there are also more rodents
23M.2.SL.TZ2.4ai: State with a reason whether pangolins are autotrophic or heterotrophic.
23M.2.SL.TZ2.i: State with a reason whether pangolins are autotrophic or heterotrophic.

Sub sections and their related questions

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4.2 Energy flow

Description

Directly related questions

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