Transcript 1.3 - glenwrightsci10

EXTINCTION IN THE
MODERN WORLD
CHAPTER 1.3
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QUESTION:
How can one of the largest population of
bird, the passenger pigeon, disappear in
only 65 years?
ANSWER:
HUMANS
HUMANS AND THE RATE OF
EXTINCTION
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Humans have had a profound effect on other
organisms.
Species extinction rates are increasing
dramatically as the human population grows.
Between 1600 – 1900 the estimate is that
one species went extinct every four years.
21 Century projection is that one species will
become extinct every 30 minutes.
HUMANS AND THE RATE OF
EXTINCTION
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Majority of threatened species can be found
in tropical rainforests
Species at risk extinction is growing, at the
rate of about 80 species per year.
BRIEF HISTORY OF
EXTINCTION
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Mass extinctions occurred before humans
existed.
Scientists believe that most mass extinctions
occurred because ASTEROIDS crashed into
the Earth.
This caused dust particles that blocked the
sun for long periods of time causing the
sunshine not to reach the surface of the
Earth.
MASS EXTINCTIONS
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438 Million years ago the first mass extinction
of marine organisms took place
360 Million years ago the same thing
happened again
245 Million years ago the largest extinction
took place destroying 80% of all species.
208 Million years ago a fourth catastrophe
occurred and the birth of dinosaurs was
created.
MASS EXTINCTIONS
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The most famous mass extinction occurred
65 million years ago, which marked the end
of the dinosaur. ( ICE AGE)
There is evidence that an asteroid hit Earth
just off the Yucatan Peninsula of Mexico.
9.6 km deep and 300 km wide. ( roughly here
to PEI)
OTHER CAUSES OF
EXTINCTION
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CLIMATE CHANGE
COMPETITION
HUMAN ACTIVITIES
Both of these cause species to adapt or die.
As a species adapts or dies this has major
effects on each ecosystem and food chain.
EFFECTS OF EXTINCTION
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The number of species in an ecosystem is
described as the biological diversity or
BIODIVERSITY of the ecosystem.
The reduction in biodiversity caused by the
extinction of a single species can cause a
“domino effect.”
When the threatened species acts as a
predator, it keeps the population of its prey in
check.
EFFECTS OF EXTINCTION
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When it acts as prey, it provides an important
food source.
So, An increase in Biodiversity = Healthy
ecosystem.
A decrease in Biodiversity = greater chance
of Ecosystem Collapse.
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SEA OTTER EXAMPLE
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Decrease in the Sea Otter ( predator )
Means an increase in Sea Urchins
Means a decrease in Kelp ( form of seaweed)
Means a decrease in Fish ( relies on
seaweed for habitat and food )
By protecting the Sea Otters caused a
increase in Fish which balanced out the food
chain and therefore the ecosystem.