Download Notebook #8 Extinctions

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ExtinctionWhen a species or an entire grouping of organisms
ceases to exist
**Most organisms that have ever lived on Earth are
now extinct!!!!
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A. Natural Factors
Volcanic eruptions and global warming
 Global cooling during ice ages
 Changes in oxygen levels in seawater
 Massive impact of asteroid or comet
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 Natural extinctions due to competition for resources or
inability to adapt to the environment have occurred
throughout geologic history
 Not all extinctions are negative-
 they clear the way for new kinds of life; opportunity exists for
another species to fil that ecological niche
 Niche- place or position
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Not all extinctions that have occurred naturally
throughout Earth’s history have had a negative
impact.
Some extinctions have often cleared the way
for new kinds of life to emerge.
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B. Man-made Factors

Cause extinction in more recent times
 Cutting of rainforests
 Removing natural habitats
 Over-harvesting
 Pollution
*More species are likely to become extinct due to humans
damaging Earth (removing survival needs of other
organisms)
*Human effects on the environment could threaten some
biological resources that humans may need
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Scientists have evidence to support claims that
humans have contributed to the extinction of many
species throughout human history, including the
woolly mammoth.
Scientists have evidence to support the claims that
many plants and animals are likely to become
extinct in the near future as a result of the negative
impact of human activities (clear-cutting, water
and air pollution, etc) on the environment.
Scientists have evidence to support the claims that
human effects on the environment could threaten
some biological resources that organisms,
including humans, may need for survival.

-species that have recently become extinct or
endangered can be studied to identify the
cause of extinction (endangerment) and
prevent it from occurring to other organisms.
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