BIOLOGY
Class Notes
10-3
Aim: Global Change
**Human induced environmental changes are affecting ecosystems worldwide and may lead
to global change.**
What does this statement mean to you?
(A) ACID RAIN
o Acidified precipitation—rain and snow that carries sulfuric acid
o Coal burning power plants send smoke into the atmosphere that has
high concentrations of sulfur
o Sulfur and water vapor=sulfuric acid
o Acid rain is the most sever in northeastern US and southeastern
Canada
o The pH of pure water is 7 (neutral)
o The pH of acid rain is 4.0-4.5 (acidic)
o Impact of acid rain
 Lakes and rivers are dying because of low pH levels
 Forests are being damaged
(B) THE OZONE LAYER
o The ozone layer is a protective shield of ozone (O3) in the upper
atmosphere
o Ozone concentration is much lower than it used to be
o When the concentration of ozone decreases, it allows more UV
radiation to reach the Earth’s surface—this can lead to many
problems for many organisms—it has also been linked to an increase
in skin cancer
o CFCs (chloroflourocarbons) are responsible for ozone destruction
o CFCs were once thought to be a harmless chemical used in air
conditioners and refrigerators
o In the atmosphere, the UV rays break the bonds of CFCs and the
free chlorine atoms then destroy the ozone layer
(C) GLOBAL TEMPERATURE
o The average global temperature has been steadily increasing—global
warming
o If our planet did not have greenhouse gases, it would be as cold as
the moon
o Greenhouse gases include—water vapor, carbon dioxide, nitrous
oxide, and methane—and are used to insulate the Earth the same way
insulation in our homes keeps us warm
o Carbon dioxide absorbs solar energy as heat radiates from Earth—
this is known as the greenhouse effect—traps heat within the
atmosphere
o Large increase in carbon dioxide in the Earth’s atmosphere is steadily
increasing the overall global temperature
o The increase is caused by—burning of fossil fuels, clearing of forests,
and urban industrialization