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BIOLOGY CHAPTER 6, SECTIONS 3-4 (edited for Keystone emphasis) SECTION 3. BIODIVERSITY
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The Value of Biodiversity
Biological diversity, or biodiversity, is the sum total of the genetically based variety of all organisms in an area (or in the entire biosphere).
One important aspect is the number of different species.
Ecosystem diversity includes the variety of habitats, communities, and ecological processes in the living world.
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3. THE VALUE OF BIODIVERSITY
Biodiversity is one of Earth's greatest natural resources.
Species of many kinds have provided us with foods, industrial products, and medicines—including painkillers, antibiotics, heart drugs, and anticancer drugs.
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Threats to Biodiversity
Human activity can reduce biodiversity by:
altering habitats
removing or reducing a population
hunting species to extinction
introducing toxic compounds into food webs
introducing foreign species to new environments
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5. THREATS TO BIODIVERSITY
Extinction occurs when a species disappears from all or part of its range.
A species whose population size is declining in a way that places it in danger of extinction is called an endangered species.
As the population of an endangered species declines, the species loses genetic diversity.
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Habitat Alteration
When land is developed, natural habitats may be destroyed.
Development often splits ecosystems into pieces, a process called habitat fragmentation.
The smaller a species’ habitat is, the more vulnerable the species is to further disturbance.
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Habitat Alteration
Examples of changes that can eliminate habitats:
Eutrophication of lakes (overgrowth due to excessive nutrients, such as algal blooms)
Deforestation of wooded area
Rising sea levels
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Pollution
Many forms of pollution can threaten biodiversity.
One of the most serious problems occurs when toxic compounds accumulate in the tissues of organisms.
DDT, one of the first pesticides, is a good example of this.
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POLLUTION
For a long time DDT was considered harmless, and it drained into rivers and streams in low concentrations.
However, DDT has two hazardous properties:
It is nonbiodegradable, which means that it cannot be broken down by organisms.
Once DDT is picked up by organisms, it cannot be eliminated from their bodies.
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POLLUTION
When DDT enters food webs, it undergoes biological magnfication.
In biological magnification, concentrations of a harmful substance increase in organisms at higher trophic levels in a food chain or food web.
In 1962, biologist Rachel Carson wrote Silent Spring, which alerted people to the dangers of biological magnification.
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11. Magnification of DDT Concentration
Pollution
Magnification of DDT Concentration
In the process of biological magnification, the concentration of a pollutant such as DDT—represented here by orange dots—is multiplied as it passes up the food chain from producers to consumers.
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12. Magnification of DDT Concentration
Pollution
Magnification of DDT Concentration
In the process of biological magnification, the concentration of a pollutant such as DDT—represented here by orange dots—is multiplied as it passes up the food chain from producers to consumers.
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13. Magnification of DDT Concentration
Pollution
Magnification of DDT Concentration
In the process of biological magnification, the concentration of a pollutant such as DDT—represented here by orange dots—is multiplied as it passes up the food chain from producers to consumers.
Copyright Pearson Prentice Hall

14. Magnification of DDT Concentration
Pollution
Magnification of DDT Concentration
In the process of biological magnification, the concentration of a pollutant such as DDT—represented here by orange dots—is multiplied as it passes up the food chain from producers to consumers.
Copyright Pearson Prentice Hall

15. Magnification of DDT Concentration
Pollution
Magnification of DDT Concentration
In the process of biological magnification, the concentration of a pollutant such as DDT—represented here by orange dots—is multiplied as it passes up the food chain from producers to consumers.
Copyright Pearson Prentice Hall

16. Magnification of DDT Concentration
Pollution
Magnification of DDT Concentration
In the process of biological magnification, the concentration of a pollutant such as DDT—represented here by orange dots—is multiplied as it passes up the food chain from producers to consumers.
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POLLUTION
The widespread use of DDT threatened populations of many animals—especially fish-eating birds like the bald eagle—with extinction.
By the early 1970s, DDT was banned in the U.S. and in most other industrialized countries; as a result, affected bird populations have recovered.
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Introduced Species
Another threat to biodiversity comes from plants and animals that humans transport around the world either accidentally or intentionally.
Invasive species are introduced species that reproduce rapidly because their new habitat lacks the predators that would control their population.
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19. The introduced species are also referred to as nonnative species.
The species already present are called native or endemic.
Ex. - a small fish, the round goby, was first reported in Pennsylvania waters in 1996.
It is competing with similar endemic fish, such as the mottled sculpin.

21. Some have been released deliberately.
INTRODUCED SPECIES
Some endemic species arrive accidentally on ships from other parts of the world.
Some have been released deliberately.
Some may have been pets that were released.

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INTRODUCED SPECIES
Nonnative species use more of the ecosystem’s resources.
They may also reduce other populations directly through predation.
Hundreds of invasive species—including zebra mussels in the Great Lakes and the leafy spurge across the Northern Great Plains—are already causing ecological problems in the United States.
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23. SECTION 4. CHARTING A COURSE FOR THE FUTURE
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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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OZONE DEPLETION
Ozone in the atmosphere protects the surface from ultraviolet (UV) radiation
Exposure to UV can:
cause cancer
damage eyes
decrease organisms' resistance to disease
damage plant leaf tissue and phytoplankton in the oceans
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OZONE DEPLETION
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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OZONE DEPLETION
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OZONE DEPLETION
Ozone depletion was caused by reactions with CFCs (chlorofluorocarbons) released into the atmosphere.
CFCs 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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29. Ozone Depletion

30. Global Climate Change
The term used to describe the increase in the average temperature of the biosphere is global warming.
Burning of fossil fuels is increasing the content of carbon dioxide in the atmosphere.

31. GLOBAL WARMING
As discussed earlier, carbon dioxide is a greenhouse gas, trapping heat in the atmosphere. The increase in carbon dioxide has led to an increase in world temperatures.

32. GLOBAL WARMING

33. Consequences of global warming:
Disruption of ecosystems - plants and animals face temperatures for which they are not adapted
Sea level is rising, due to melting ice caps plus expansion of the ocean water. This floods coastal areas with unique ecosystems.
Increased floods, droughts, and severe storms.
Droughts can lead to wildfires