Ecosystems

Chapter 54

I. Energy Flow

A. Trophic StructuresB. Energy Budget

Global EBGPP & NPPBiomassLimits of PP- aquatic, terrestrial

C. Secondary ProductivityEnergy EfficiencyPyramids-production, #s, biomass

D. Biological Magnification

II. Biogeochemical Cycles

A. WaterB. CarbonC. NitrogenD. Phosphorous

III. Human Impact

A. Chemical CyclesB. Acid precipitationC. Toxins & biological

MagnificationD. Climate change-CO2 & O3

A. Trophic Structures- Energy Flow

Energy flow one way- sun is inflowFood chains & webs are short b/c trophic

energy level loses 90%

Energy Transfer Energy in

from the Suncaptured by autotrophs

= producers Energy moves through

food chain transfer of energy

from autotrophs to heterotrophs (herbivores to carnivores)

heterotrophs = consumers

Energy Transfer

Primary producers primary consumers secondary consumers tertiary consumers

Detrivores/Decomposers get energy from detritus most important part in an ecosystem connects all levels

B. Energy Budget Primary Production

Producers determine the energy budget for an ecosystemGPP amount of solar energy

converted into chemical energy all photsynthesis

NPP = GPP- Respiration (cost of staying alive)

PP J/m2/y or biomass

Primary Production

Aquatic Systems light & nutrients are limiting factors for PP

Terrestrial Systems temperature, moisture, nutrients

C. Secondary Production

The mount of chemical energy in consumers’ food that is converted into their

Energy Inefficiency

incompletedigestion

metabolism

Pyramids of Production represent the loss of energy from a food chain

how much energy is turned into biomass

Pyramid of Numbers levels in pyramids of production are

proportional to number of individuals present in each trophic level

Implications Dynamics of energy through ecosystems

have important implications for human populationswhat food would be more ecologically sound?

D. Biological Magnification Toxins can become concentrated in

successive trophic levels of food webs Humans produce many toxic chemicals that

are dumped into ecosystems. These substances are ingested and

metabolized by the organisms in the ecosystems and can accumulate in the fatty tissues of animals.

These toxins become more concentrated in successive trophic levels of a food web, a process called biological magnification.

The pesticide DDT, before it was banned, showed this affect.

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Fig. 54.24

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 54.25

Biogeochemical Cycles

Nutrient cyclesGases cycle on a global

levelSolids cycle slowly and

locally

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Fig. 54.15

The water cycle is more of a physical process than a chemical one.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin CummingsFig. 54.16

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin CummingsFig. 54.17

The carbon cycle fits the generalized scheme of biogeochemical cycles better than water.

The Nitrogen Cycle Nitrogen enters ecosystems

through two natural pathways.Atmospheric deposition, where

usable nitrogen is added to the soil by rain or dust.

Nitrogen fixation, where certain prokaryotes convert N2 to minerals that can be used to synthesize nitrogenous organic compounds like amino acids.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 54.18

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin CummingsFig. 54.19

III. Human Impact

Rising atmospheric CO2.Since the Industrial Revolution, the

concentration of CO2 in the atmosphere has increased greatly as a result of burning fossil fuels.

Measurements in 1958 read 316 ppm and increased to 370 ppm today

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 54.26

The Greenhouse Effect Rising levels of atmospheric CO2 may

have an impact on Earth’s heat budget. When light energy hits the Earth, much of it is

reflected off the surface. CO2 causes the Earth to retain some of the

energy that would ordinarily escape the atmosphere.

This phenomenon is called the greenhouse effect.

The Earth needs this heat, but too much could be disastrous.

Global Warming Scientists continue to construct models to

predict how increasing levels of CO2 in the atmosphere will affect Earth.Several studies predict a doubling of CO2 in

the atmosphere will cause a 2º C increase in the average temperature of Earth.

Rising temperatures could cause polar ice cap melting, which could flood coastal areas.

It is important that humans attempt to stabilize their use of fossil fuels.

Ozone Depletion Life on earth is

protected from the damaging affects of ultraviolet radiation (UV) by a layer of O3,or ozone.

Studies suggest thatthe ozone layer hasbeen gradually“thinning” since 1975.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 54.27b

Ozone Depletion Probably results from the accumulation of

chlorofluorocarbons, chemicals used in refrigeration and aerosol cans, and in certain manufacturing processes.

The result of a reduction in the ozone layer may be increased levels of UV radiation that reach the surface of the Earth.

This radiation has been linked to skin cancer and cataracts.

The impact of human activity on the ozone layer is one more example of how much we are able to disrupt ecosystems and the entire biosphere.