Exam 3 #11

UIC BioS 101 Nyberg

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ECOSYSTEM Studies
Energy Flow

Ecosystem studies measure the flow (= movement =flux) of Energy and Materials in an area (= Community).

Trophic, about or relating to nourishment

Speaker Notes:

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Exam 3 #11

UIC BioS 101 Nyberg

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READING ASSIGNMENT

• Chapter 54 in Freeman

• This lecture focuses on the flow of energy, section 54.1. The following lecture focuses on cycling of materials, especially biologically important elements.

Speaker Notes:

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UIC BioS 101 Nyberg

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ENERGY versus MATERIALS

• The energy source of life on earth (the sun) is external to the earth.

  • The amount of energy utilized by life is a small fraction of the available energy.

• The materials necessary for life are limited to what is on the earth.

  • Materials must be recycled through various forms in the living and non-living world.

Speaker Notes:

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The “unutilized” energy heats the earth and atmosphere that is part of the system that life has evolved in. Capturing wind energy will have biological consequences just as has capturing hydroelectric power.

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Exam 3 #11

UIC BioS 101 Nyberg

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BASIC ENERGY FLOW

• SUN

PRODUCERS (Autotrophs)

CONSUMERS (Heterotrophs)

Flow (= flux) from one compartment to another

1022 Joules per day for earth

Speaker Notes:

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Flux means flow from one compartment (place) to another.

The cross-sectional area of the earth is 1.275 x 10^14 m^2.

So energy from sun is about 10^8 Joules/m^2 day = 3x10^9 Joules /yr = 1.2*10^6 kcal/yr.

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UIC BioS 101 Nyberg

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Energy source:

1,254,000

kcal/m2/year

Speaker Notes:

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Caption: In a temperate forest ecosystem, energy from sunlight is transformed to chemical energy by photosynthesis. The products of photosynthesis go, in part, to fuel new plant growth. Plant tissue is either consumed by herbivores in the grazing food web or falls into the decomposer food web when the plant dies.

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Exam 3 #11

UIC BioS 101 Nyberg

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Doing the SUMS of energy & material

• In studying energy flow we expect the inputs of a compartment to equal the outputs because energy is conserved.

• Matter is also conserved. In biological compartments inputs of material will equal the amount stored by the compartment plus the output into other systems/compartments.

Speaker Notes:

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For material the residence time is the average length of time an atom spends in the compartment.

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UIC BioS 101 Nyberg

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Energy Flow Diagram

RESPIRATION

Dead Organic Matter

Speaker Notes:

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GPP = Gross Primary Production is all the energy captured by producers. The part producers respire is not available to consumers. The energy capture by plants that is available to consumers is NPP, Net Primary Productivity.

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Exam 3 #11

UIC BioS 101 Nyberg

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Measuring Energy

• E = m•c2 units are g•m2•sec-2

• 1 Joule = 1 kg•m2•sec-2

• 1 calorie = heat necessary to raise 1 g of water 1° C = 0.239 Joule

• 1000 calories = 1 kcal = 1 Calorie

• Net Primary Productivity (capture of energy and materials) is often measured in grams of biomass per m2 per year.

Speaker Notes:

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Grams of biomass (weighed dry) is a lot easier to determine than energy.

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UIC BioS 101 Nyberg

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NPP varies a lot

Speaker Notes:

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UIC BioS 101 Nyberg

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Productivity

• Gross primary productivity GPP is the amount of energy captured in photosynthesis (including that which is respired by the plant).

• Net primary productivity NPP is the amount of energy captured by the plant that remains in the plant (is available to consumers).

• Commonly measured in grams (dry) weight per square meter per year

Speaker Notes:

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Productivity varies greatly around the world. Water is an important limiting factor.

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UIC BioS 101 Nyberg

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0–100

100–200

200–400

400–600

600–800

>800

Productivity ranges

(g/m2/yr)

Figure 51.3a

Terrestrial productivity

Productivity

Positively correlated with amount of precipitation

Speaker Notes:

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The terrestrial ecosystems with the highest primary productivity are found in the tropics, where warm temperatures and high moisture encourage high photosynthetic rates. Tundras and deserts have the lowest productivity.

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Exam 3 #11

UIC BioS 101 Nyberg

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Productivity by Biome

• Though the productivity per unit area of the ocean is low, open ocean is so much more abundant than other communities that it is a big contributor to the earth’s total.

• Tropical forests and wetlands have the highest productivity per unit area of terrestrial communities.

Speaker Notes:

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Light and CO2 do not vary as much spatially as the supply of water.

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UIC BioS 101 Nyberg

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CONSUMERS

• Consumers are heterotrophs dependent on reduced carbon compounds produced by autotrophs

• Consumers can be divided into three basic levels

  • Herbivores organisms that eat plants

  • Carnivores organisms that eat animals

  • Decomposers organisms that utilize non-living reduced carbon compounds

Speaker Notes:

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Autotrophs = Producers

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UIC BioS 101 Nyberg

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Use of energy by consumers

• Efficiency of use into growth and reproduction varies greatly among species.

• OUTPUT Categories

  • Growth and Reproduction

  • Excretion (includes egestion)

  • Respiration (used to generate motion)

• Measures of available energy based on living in oxygen atmosphere.

Speaker Notes:

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Where does the stuff you eat go?

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UIC BioS 101 Nyberg

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Use of Energy by a mammal

Speaker Notes:

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Mammals and birds respire a lot higher percentage of consumption than other animals. How does this figure fit in with Fig. 54.7?

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Exam 3 #11

UIC BioS 101 Nyberg

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Carnivores

• Carnivores can be divided into

  • Primary carnivores, animals that eat herbivores

  • Secondary carnivores, animals that eat primary carnivores

  • Tertiary carnivores are those that primarily get energy from secondary carnivores

• Carnivores that eat decomposers have no special name

Speaker Notes:

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What animals do you know that eat only other carnivores?

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UIC BioS 101 Nyberg

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Production of Biomass - Terrestrial

Speaker Notes:

Pyramids of production and pyramids of biomass may be very different.

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UIC BioS 101 Nyberg

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FOOD chains

Speaker Notes:

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The ‘food chain’ is a fairly recent idea in biology. It has been used as a description of human social organization.

Trophic level refers to place in the food chain or web.

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UIC BioS 101 Nyberg

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Food Webs

Speaker Notes:

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In most natural systems a food web is probably more realistic than a food chain.

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UIC BioS 101 Nyberg

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Omnivore

• An animal that gains significant energy from more than one trophic level.

• Crayfish are omnivores.

• Many carnivores depend on plant products, especially fruit, for energy

  • Bear

  • Raccoon

Speaker Notes:

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Humans are omnivores.

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UIC BioS 101 Nyberg

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Decomposer Food Web

Speaker Notes:

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What organisms do you know that eat dead organisms?

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UIC BioS 101 Nyberg

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Problem

• Use Figure 54.8 to calculate the NNP at Hubbard Brook Forest in kcal•m-2•yr-1.

• Convert the energy units to the conventional g•m-2•yr-1 using the estimate of 4 kcal = 1g.

• Compare your value to the Figure 54.3 value for temperate deciduous forest.

Speaker Notes:

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What units are you going to use to keep track of energy?

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UIC BioS 101 Nyberg

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Vocabulary

• Autotroph/producer

• Consumer/heterotroph

• Productivity

• Decomposer

• Herbivore

• Carnivore

• Omnivore

• Food web

• Respiration

• net primary production =NPP

• gross primary production =GPP

• Trophic level

• Joules

Speaker Notes:

Energy units are not simple to convert, because so many different units are used.

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