Lesson 7.2: Extinction and Biodiversity Loss
Lecture Notes
Unit 7: Biodiversity
Natural Biodiversity Loss:
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____________________: Naturally occurring extinctions, occurring one species at a time
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________________: Events when extinction rates far exceed the normal background rate
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There have been __________ mass extinctions in Earth’s history.
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Each time, more than ______of all families and _____of all species have gone extinct.
Biodiversity at Risk:
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The current extinction rate is ____to ____ times greater than the natural background rate.
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In 2009, 1321 species in the U.S. were classified as _____________or ______________.
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_________________: At serious risk of extinction
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_________________: Likely to become endangered soon through all or part of its range
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_________________: Summarizes global population trends for certain terrestrial,
freshwater, and marine species
Causes of Biodiversity Loss:
1.
3.
2.
4.
Habitat Change and Loss:
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Greatest cause of biodiversity loss
Organisms, adapted to their ____________, decline in __________when the habitat
changes.
______________________: Patches of suitable habitat surrounded by unsuitable habitat
In general, _________ habitat fragments can support ________biodiversity than
____________ fragments.
Invasive Species, Pollution, and Overharvesting:
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Invasive species can out-compete and displace native species.
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Harmful chemicals and materials that make their way into habitats can poison people and
wildlife.
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Occasionally, species can be driven toward extinction by hunting or overharvesting by
humans.
o Examples include:_________________________________________
Climate Change:
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Increasingly becoming a factor in biodiversity loss
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Unlike the other factors, climate change will have a
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THINK.PAIR.SHARE NOTE SECTION:
THINK: Suppose someone tells you that human development increases biodiversity.
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When a forest is fragmented, he or she argues, new habitats, such as grassy lots and
gardens, may be introduced to an area and allow additional species to live there.
How would you respond to this claim?
Do you agree? Explain your answer.
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