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ENERGY FLOW. READINGS: FREEMAN, 2005 Chapter 54 Pages 1247-1252. ECOSYSTEMS, THERMODYNAMICS AND ENERGY FLOW. The concept of energy flow in ecosystems is a cornerstone of ecology.

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ENERGY FLOW

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Energy flow l.jpg

ENERGY FLOW

READINGS:

FREEMAN, 2005

Chapter 54 Pages 1247-1252


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ECOSYSTEMS, THERMODYNAMICS AND ENERGY FLOW

  • The concept of energy flow in ecosystems is a cornerstone of ecology.

  • Energy flow in ecosystems is based on the assumption that the laws of thermodynamics apply to all observable nature and thus apply to trophic levels.


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Two Laws of Matter and Energy

  • Matter and energy can not be created or destroyed. The law of conservation of matter and energy.

  • When energy is changed from one form to another some is always degraded into heat. Energy transfer is never 100% efficient.


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Two Laws of Matter and Energy

The implication of these two laws of matter and energy are that:

  • MATTER CAN BE RECYCLED.

  • ENERGY CAN NOT BE RECYCLED.

    Thus, these two laws of nature govern the recycling of matter and the flow of energy.


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A Model for the Cycling of Matter and Flow of Energy


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A Model of Energy (Transfer) from One Trophic Level to Another


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A Model of Energy (Transfer) from One Trophic Level to Another

Each successive transfer of energy results in less and less available energy since each trophic level converts some incoming energy to low grade heat through respiration.


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Energy Budget for Producers

  • Gross Production (Photosynthesis) = Net Primary Production + Respiration.

  • Net Primary Production = Growth and Reproduction + Transfer to 1o Consumers (Herbivory) + Transfer to Decomposers (Decomposition)


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Energy Budget for Producers

  • Producers are able to capture solar energy and convert to chemical bond energy.

  • Much of that energy they used for cellular respiration.

  • Some of that energy is consumed by herbivores.

  • Some becomes part of dead tissue and is passed on to decomposers.

  • Some is stored as growth and reproduction.


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An Energy Budget for Producers


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Energy Budget for Consumers

  • Primary (1o) consumers obtain their energy from producers. They use it in respiration, store it by growth and reproduction, pass it on to higher level consumers when they are eaten and along to decomposers when they die.

  • Secondary and higher level consumers do the same.


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How Is Energy Measured?

The quantity of energy associated with organic matter is measured in a calorimeter. In this instrument a measured portion of biomass is burned in pure oxygen and the heat absorbed by water is measured either in small calories (cal), large calories (kilocal) or food calories (Cal).


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How Much Energy Is Associated With A Given Type of Biomass

  • 1 gram of carbohydrate = 4 kcal

  • 1 gram of protein = 4 kcal

  • 1 gram of fat (lipid) = 9 kcal

  • 1 gram of average plant biomass

    = 2 kcal (wet weight)

    = 4.5 kcal (dry weight)

  • 1 gram of average animal biomass

    = 2.5 kcal (wet weight)

    = 5.5 kcal (dry weight)


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ENERGY (BIOMASS) AND CONSUMPTION

  • Consumption refers to the intake and use of matter and energy by animal taxa in an ecosystem.

  • Consumption is measured in kilocalories or grams of biomass.

  • The energy budget for an animal population is determined by the amount of food ingested, egested and assimilated.

  • Assimilated energy goes to respiration and for growth and reproduction.


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The Arithmetic of Consumption

# INGESTED = # EGESTED + ASSIMILATED

# ASSIMILATED = # USED FOR RESPIRATION +

# STORED AS GROWTH & REPRODUCTION


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Energy Flow Through Chipmunk Population at Hubbard Brook

  • Chipmunks are important consumers in both the green and brown food webs in this forest.

  • Important elements of their diet are beech and maple seeds.


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Energy Flow Through Chipmunk Population at Hubbard Brook

  • Ecologists determined that the chipmunks in Hubbard Brook ingested 31 kcal of food energy and egested 5.5 kcal. How much did they assimilate?

  • If the chipmunks, stored through growth and reproduction 0.5 kcal, how much energy was released in respiration?

31 kcal

0.5 kcal

5.5 kcal

????

????

0.21 g/m2/year


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Energy Flow Through Chipmunk Population at Hubbard Brook

  • Ecologists determined that the chipmunks in Hubbard Brook ingested 31 kcal of food energy and egested 5.5 kcal. How much did they assimilate?

  • If the chipmunks, stored through growth and reproduction 0.5 kcal, how much energy was released in respiration?

31 kcal

0.5 kcal

5.5 kcal

25.5 kcal

????

0.21 g/m2/year


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Energy Flow Through Chipmunk Population at Hubbard Brook

  • Ecologists determined that the chipmunks in Hubbard Brook ingested 31 kcal of food energy and egested 5.5 kcal. How much did they assimilate?

  • If the chipmunks, stored through growth and reproduction 0.5 kcal, how much energy was released in respiration?

31 kcal

0.5 kcal

5.5 kcal

25.5 kcal

25 kcal

0.21 g/m2/year


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Chipmunk Energy Budget Expressed as %


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Energy Flow Through Salamander Population at Hubbard Brook

  • Four species of salamanders and one species of newt are found in Hubbard Brook.

  • Their biomass equals that of the chipmunk population.


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Energy Flow Through Salamander Population at Hubbard Brook

  • Salamanders egested 0.2 kcal and assimilated 0.86 kcal. How much did they ingest?

  • If the salamanders, used 0.34 kcal in respiration, how much energy was stored through growth and reproduction?

?????

????

0.2 kcal

0.86 kcal

0.34 kcal

0.20 g/m2/year


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Energy Flow Through Salamander Population at Hubbard Brook

  • Salamanders egested 0.2 kcal and assimilated 0.86 kcal. How much did they ingest?

  • If the salamanders, used 0.34 kcal in respiration, how much energy was stored through growth and reproduction?

1.06 kcal

????

0.2 kcal

0.86 kcal

0.34 kcal

0.20 g/m2/year


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Energy Flow Through Salamander Population at Hubbard Brook

  • Salamanders egested 0.2 kcal and assimilated 0.86 kcal. How much did they ingest?

  • If the salamanders, used 0.34 kcal in respiration, how much energy was stored through growth and reproduction?

1.06 kcal

0.52 kcal

0.2 kcal

0.86 kcal

0.34 kcal

0.20 g/m2/year


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Why do chipmunks use more energy than salamanders?


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A Model of Energy (Transfer) from One Trophic Level to Another


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Energy Flow Through the Hubbard Brook Ecosystem


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Energy Flow Through the Hubbard Brook Ecosystem

  • Gross Production (Photosynthesis) = Net Primary Production + Respiration.

    Net Production =10,400 - 5,720 = 4,680

  • Net Primary Production = Growth and Reproduction + Transfer to 1 Consumers (Herbivory) + Transfer to Decomposers (Decomposition)

    Growth and Reproduction = 4,680 - 2,864 - 617

    = 1,199


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Energy Flow Through the Hubbard Brook Ecosystem


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Energy Flow Through the Hubbard Brook Ecosystem


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Energy Flow Through the Hubbard Brook Ecosystem

# INGESTED = # EGESTED + ASSIMILATED

ASSIMILATED = 617 + 22 - 504 = 135

# ASSIMILATED = # USED FOR RESPIRATION +# STORED AS GROWTH & REPRODUCTION

# USED FOR RESPIRATION = 135 - 0


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Energy Flow Through the Hubbard Brook Ecosystem


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Energy Flow Through the Hubbard Brook Ecosystem

  • Biomass of trees is increasing.

  • More energy (Net Production) flows through the “brown” food web than through the “green” food web. What is the clue in Fall?


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Energy Flow Through Human Ecosystems

  • For more than 1/2 million years, humans obtained food energy as hunters and gathers in natural ecosystems. This way of life was maintained by the !Kung Bushman until recently.

  • Modern agriculture, which utilizes fossil fuels, has been in existence for less than 100 years. U.S. agriculture, one of the most productive in all time, is a symbol of this way of life.


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Energy Flow In A !Kung Bushman Managed Ecosystem

  • The !Kung, until recently, obtained food from populations of plants and animals in the Kalahari Desert.

  • Mongongo nuts1, small quantities of plants20 (roots, melons, gums, bulbs, dried fruit) and game animals16-28 provided about 2355 kcal/person/day (more than adult male requirement of 2250).

Number of species


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Energy Flow In A Modern Agricultural Ecosystem

  • The average American relies on domesticated plants and animals to meet his or her caloric requirements.

  • Cereal grains (grasses5), lesser quantities of other plants20-40 and domesticated livestock4 meet our caloric requirements.

Energy in corn equivalents


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Who Has the Most Sustainable Way of Meeting Caloric Requirements?

  • Sustainability is currently being defined in more precise terms, but it includes ability to meet energy needs and preserve environmental quality (avoid pollution, etc).


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Energy Flow In An Industrialized Country (Scotland)

Energy use measured in terra watt hours


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Energy Flow and CO2 Emissions in the United States (2000)


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Energy Future Beyond Carbon

  • A special issue of SCIENTIFIC AMERICAN (September, 2006) poses some energy solutions for a sustainable world.

  • It describes: “How to Power the Economy and Still Fight Global Warming”.

  • Provides a critical look at cleaning up coal, nuclear option, hydrogen to fuel cars, biofuels and renewables, and the dreams of fusion.


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Your Understanding of Energy Flow Has Important Future Consequences. Check It Out With Your Answer To This Question?

One winter 7 sailors are shipwrecked on a barren artic island that has water but neither soil or vegetation. A crate of corn flakes and a crate containing 7 hens are also cast ashore with them. To survive as long as possible the sailors should:

a. kill & eat the hens, then eat the cornflakes.

b. feed the corn flakes to the hens, then eat the

eggs.

c. eat the cornflakes & let the hens fend for

themselves.


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ENERGY FLOW

READINGS:

FREEMAN, 2005

Chapter 54 Pages 1247-1252


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