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The Sixth Extinction?
Topic 7
Biological Diversity
In the last 600 million years
there have been five major
declines in Earth’s biodiversity.
The 6th Extinction
Relative Species
Diversity
Human Impact on
Biodiversity
Some areas of the world support
more biodiversity than others.
What factors influence diversity?
– Heat
– Light
– Rainfall
Disappearing Habitats
Bioindicator Species: a species
in an ecosystem that when their
population starts to decline
indicate that there is a problem
with the ecosystem.
Disappearing Habitats
Grizzlies (and other large
carnivores) are thought to be a
bioindicator species.
Grizzlies used to roam throughout
North America. The disappearance
of Grizzlies from Mexico and most
of the United States is called
extirpation.
Disappearing Habitats
One of the first effects of
human interference in an
ecosystem is the loss of the
large carnivores usually found
in the ecosystem.
Human Impact on Rain
Forest Ecosystems
Human populations are growing more
than ever before.
Larger population increases demands
on environment.
– Natural habitats are being cleared for
farming and housing.
– Increases in logging and mining lead to
increases in pollution.
Human Impact on Rain
Forest Ecosystems
Rain Forests are areas the
highest bio diversity in the
world.
It is being cut down at a rate of
about 1% per year.
The Population
Explosion
Population growth is not spread equally
around the world.
Developing nations are usually hardest
hit by the population explosion.
Space has to be cleared on the land to
make space for the population growth.
This leads to clearing of rain forests
which can lead to extinction of some
species.
Human Activities and
Extinction
Humans have not always been
aware of their impact on the
survival species as we are today.
Technology has given us the ability
to preserve biodiversity; but
technology also has increased our
ability to use up resources leading
to damage to the environment.
Human Impacts
– About 10 000 years ago it is thought that
humans hunted woolly mammoths to
extinction.
– Large animals have been almost hunted to
extinction in Madagascar, Australia and
New Zealand.
– In the late 1800s Passenger Pigeons were
hunted so much in the eastern North
America that they went from the world’s
most abundant bird to extinction in about
100 years.
Extinction