Ecosystems

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9

Global warming can be slowed by reducing energy needs and converting to renewable sources of energy.

Stabilizing CO2 emissions will require an international effort.

Slide 53

Depletion of Atmospheric Ozone

Life on Earth is protected from damaging effects of UV radiation by a protective layer of ozone molecules in the atmosphere.

Satellite studies suggest that the ozone layer has been gradually thinning since 1975.

Destruction of atmospheric ozone probably results from chlorine-releasing pollutants such as CFCs (chloroflorocarbons) produced by human activity.

Slide 54

How free chlorine in the atmosphere destroys ozone

O2

Sunlight

Cl2O2

Chlorine

Chlorine atom

O3

O2

ClO

ClO

Slide 55

Scientists first described an “ozone hole” over Antarctica in 1985; it has increased in size as ozone depletion has increased.

Ozone depletion causes DNA damage in plants and poorer phytoplankton growth.

An international agreement signed in 1987 has resulted in a decrease in ozone depletion.

Slide 56

Erosion of Earth’s ozone shield

(a) September 1979

(b) September 2006

Slide 57

Review

Fossilization

Organic

materials

available

as nutrients

Living

organisms,

detritus

Organic

materials

unavailable

as nutrients

Coal, oil,

peat

Burning

of fossil

fuels

Respiration,

decomposition,

excretion

Assimilation,

photosynthesis

Inorganic

materials

available

as nutrients

Inorganic

materials

unavailable

as nutrients

Atmosphere,

soil, water

Minerals

in rocks

Weathering,

erosion

Formation of

sedimentary rock

Slide 58

You should now be able to:

Explain how the first and second laws of thermodynamics apply to ecosystems.

Define and compare gross primary production, net primary production, and standing crop.

Explain why energy flows but nutrients cycle within an ecosystem.

Explain what factors may limit primary production in aquatic ecosystems.

Slide 59

Distinguish between the following pairs of terms: primary and secondary production, production efficiency and trophic efficiency.

Explain why worldwide agriculture could feed more people if all humans consumed only plant material.