Chapter 55

Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition Solomon • Berg • Martin

Chapter 55

Humans in the Humans in the EnvironmentEnvironment


Biology, Seventh Edition CHAPTER 55 Humans in the Environment

• Biological diversity• Variety of organism considered at

three levels–Genetic diversity–Species diversity–Ecosystem diversity

• Decreasing worldwide



• Extinct species• All members of the species are

dead

• Endangered species• In imminent danger of extinction

• Threatened species• Population is quite small, but

extinction is less imminent



An extinctspecies



• Four causes of declining biological diversity• Most significantly, habitat loss and

fragmentation• In addition, pollution, introduction of

invasive species, pest and predator control, and commercial activity



Percentage of imperiled U.S. species that are threatened by various human activities



• Conservation biology• Study of how humans affect

organism• Development of ways to protect

biological diversity



Habitat destruction



Biodiversity hotspots



• In situ conservation• Efforts to preserve biological

diversity in the wild

• Ex situ conservation• Efforts to preserve biological

diversity in human-controlled settings



• Endangered Species Act (ESA)• Authorizes the U.S. Fish and

Wildlife Service to protect bio-diversity domestically and abroad

• CITES• International organization to protect

species from illegal international wildlife trade



Illegal commercial harvesting



Organisms listed as endangered or threatened in the U.S., 2003



• Forests provide many ecosystem services• Watershed protection• Soil erosion prevention• Climate moderation• Protection from flooding• Wildlife habitat

• Greatest problem is deforestation



Deforestation



• Greenhouse gases • Carbon dioxide• Methane• Surface ozone• Nitrous oxide• Chlorofluorocarbons

• Causes greenhouse effect and global warming and enhanced greenhouse effect



Mean annual global temperature,1960 to 2002



• Surface Ozone • Ozone (O3) is a form of oxygen• Human-made pollutant in lower

atmosphere• Occurs naturally in the stratosphere



• Ozone destruction in the stratosphere• Amount of ozone in the stratosphere

is declining (ozone depletion)• Large areas of ozone thinning over

Antarctica and the Arctic• Excessive exposure to UV radiation

linked to human disease, i.e., skin cancer



Increase in greenhouse gases, preindustrial to present



Enhanced greenhouse effect



UV radiation and the ozone layer



Ozone thinning

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Chapter 55

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