1. 6-4 Charting a Course for the Future
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2. What are two types of global change of concern to biologists?
Ozone Depletion
What are two types of global change of concern to biologists?
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3. 6-4 Charting a Course for the Future
Researchers are gathering data to monitor and evaluate the effects of human activities on important systems in the biosphere. Two of these systems are:
the ozone layer high in the atmosphere
the global climate system
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4. Exposure to UV can: Ozone Depletion cause cancer damage eyes
decrease organisms' resistance
to disease
damage plant leaf tissue and
phytoplankton in the oceans
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5. Early Evidence
In the 1970s, scientists discovered a hole in the ozone layer over Antarctica.
After it was first discovered, the ozone hole grew larger.
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7. CFCs (chlorofluorocarbons) were once widely used:
One Solution
CFCs (chlorofluorocarbons) were once widely used:
as propellants in aerosol cans
as coolant in refrigerators, freezers, and air conditioners
in the production of plastic foams
The U.S. and other nations began reducing the use of CFCs in 1987, and eventually banned them.
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8. Ozone Depletion
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9. Global Climate Change
Global Climate Change The term used to describe the increase in the average temperature of the biosphere is global warming. One sign of global warming is melting polar ice.
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Biologists are concerned about global warming. This map of the Arctic is based on images taken by satellites in 1979 and Sea ice in the Arctic Ocean has receded so quickly that some scientists suggest that, within the next 50 years, the ice could disappear completely.

11. Evidence of Global Warming
The geological record shows that Earth’s climate has changed repeatedly during its history.
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Human society depends on healthy, diverse, and productive ecosystems because of the environmental and economic benefits they provide.

15. The Value of a Healthy Biosphere
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Human society depends on healthy, diverse, and productive ecosystems because of the environmental and economic benefits they provide.

16. 6-4 An increase in the average temperature of the biosphere is called
the greenhouse effect.
global warming.
ozone depletion.
climate control.
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17. 6-4 The geological record indicates that Earth’s climate has
remained essentially the same throughout history.
been constant until humans have influenced the environment.
changed dramatically every 150 years.
repeatedly changed over its history.
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18. 6-4 A possible effect of global warming is
extinction of organisms in areas where they once thrived.
an increase in global surface temperature of 20 Celsius degrees.
a sharp decrease in the temperature of the waters off the coast of California.
complete elimination of the protective ozone layer in the atmosphere.
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19. 6-4 Depletion of Earth’s protective ozone layer results in
a decrease in the amount of heat that reaches the surface.
a decrease in the amount of UV radiation that reaches the surface.
an increase in the amount of rainfall.
an increase in the amount of UV radiation that reaches the surface.
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20. 6-4 The most likely cause of ozone depletion is the
addition of carbon dioxide to the atmosphere.
increase in UV radiation from the sun.
addition of chemicals developed for use in refrigeration and aerosol cans.
increase in the amount of smog produced by automobiles.
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