Transcript chapter44_Sections 4-7.ppt

Cecie Starr
Christine Evers
Lisa Starr
www.cengage.com/biology/starr
Chapter 44
Human Effects on the Biosphere
(Sections 44.4 - 44.7)
Albia Dugger • Miami Dade College
44.4 Acid Rain
• Pollutants disrupt physiological processes of organisms
• Sulfur dioxides from coal-burning power plants, and nitrogen
oxides from burning gas and oil, are common air pollutants
• pollutant
• Substance that is released into the environment by human
activities and interferes with the function of organisms that
evolved in the absence of the substance or with lower
levels
Acid Rain (cont.)
• Dry acid deposition occurs when dry dust particles coated
with airborne sulfur and nitrogen fall to the ground
• Wet acid deposition (acid rain) occurs when pollutants
combine with water and fall as acidic precipitation
• acid rain
• Low pH rain that forms when sulfur dioxide and nitrogen
oxides mix with water vapor in the atmosphere
Acid Rain (cont.)
• Acid rain in aquatic habitats prevents fish eggs from
developing and kills adult fish
• Acid rain in forests burns tree leaves, and makes trees more
susceptible to insects and pathogens
• Acid rain alters composition of soils
• Positive hydrogen ions displace positive nutrient ions such
as calcium, causing nutrient loss
• Acidity causes soil particles to release metals such as
aluminum that harm plants
Average Precipitation Acidities
Effects of Acid Rain
ANIMATION: Acid deposition
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44.5 Biological Effects
of Chemical Pollutants
• Chemicals released by human activities can accumulate in
the bodies of organisms and interfere with metabolism
• bioaccumulation
• An organism accumulates increasing amounts of a
chemical pollutant in its tissues over the course of its
lifetime
Accumulation and Magnification
• In animals, hydrophobic chemical pollutants ingested or
absorbed across the skin accumulate in fatty tissues
• Pollutant concentration in tissues increases with age, and with
trophic level (biological magnification)
• biological magnification
• A chemical pollutant becomes increasingly concentrated
as it moves up through food chains
Biological Magnification of DDT
• As a result of bioaccumulation and biological magnification,
even seemingly low environmental concentrations of
pollutants can have major detrimental effects on a species
• During the 1960s, ospreys were driven toward extinction by
widespread use of DDT, because this chemical interferes with
their egg shell formation
Biological Magnification of DDT
• Concentration of DDT in
osprey tissues was
276,000 times higher
than that in the water
Biological Magnification of DDT
Point and Nonpoint Sources
• Pollutants that come from a few easily identifiable sites (point
sources) – such as a factory – are the easiest to control
• Pollution from widespread release of a pollutant (nonpoint
sources) – such as oil that drips from vehicles – is more
difficult to control
ABC Video: Pharmaceuticals in Water Supplies
BBC Video: Pesticides: Will More Restrictions
Help or Hinder?
44.6 The Trouble With Trash
• Trash buried in the ground (such as lead from batteries) can
contaminate groundwater
• Trash dumped at sea (such as plastics) harms marine life
• Plastic and other garbage that enters our coastal waters
persists for many years
• To reduce the impact of plastic trash, avoid buying plastics, or
be sure to recycle or dispose of them properly
Effects of Discarded Plastics
• Seabirds often mistake
floating bits of plastic for
food, and feed them to
their chicks, with deadly
results
• This Laysan albatross
chick was fed more than
300 pieces of plastic by
its parents
BBC Video: Plastic Bag Charge Debated
44.7 Ozone Depletion and Pollution
• Ozone is said to be “good up high, but bad nearby”
• In the upper atmosphere, ozone absorbs most incoming
ultraviolet (UV) radiation that damages DNA and causes
mutations – but near the ground, it is a harmful pollutant
• ozone layer
• High atmospheric layer with a high concentration of ozone
(O3) that prevents much ultraviolet radiation from reaching
Earth’s surface
Depletion of the Ozone Layer
• In the mid-1970s, scientists noticed that Earth’s ozone layer
(10.5 to 17 miles above sea level) was thinning, particularly
over Antarctica (the “ozone hole”)
• In 1987, countries worldwide agreed to phase out production
of chlorofluorocarbons (CFCs) and other ozone-destroying
chemicals – but existing CFCs break down very slowly
The Ozone Hole
• Ozone levels in the
upper atmosphere in
September 2007
• Check the ozone hole’s
current status at:
http://ozonewatch.gsfc.
nasa.gov/
Concentration of CFCs
in the Upper Atmosphere
Near-Ground Ozone Pollution
• Near the ground, ozone irritates eyes and respiratory tracts of
humans and wildlife, and interferes with plant growth
• Ground-level ozone forms when nitrogen oxides and volatile
organic compounds released by burning or evaporating fossil
fuels are exposed to sunlight
• Warm temperatures speed the reaction
ANIMATION: How CFCs destroy ozone
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ANIMATION: The GreenHouse Effect
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BBC Video: Who Pays the Price for
Technology?