Transcript Science 9: Unit A: Biological Diversity

Science 9: Unit A:
Biological Diversity
Topic 7: The Sixth Extinction?
Trend for Biodiversity
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Traditionally new species have formed
faster than they have gone extinct leading
to greater biodiversity.
In the last 65 million years, this trend has
reversed. 70 species/day have been going
to extinct.
Again, the closer you get to the equator, the
increased the biodiversity.
Bottleneck Events=Great Extinctions
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There have been five cataclysmic events
that have greatly reduced the biodiversity in
the world. These events affect many
different species of organisms.
Some biologists refer to the arrival of
humans as the Sixth extinction referring to
our effect on biodiversity.
Human Impact on Biodiversity
I. Pollution has made many habitats
unsuitable for the organisms living there.
Acid rain, polluted streams and oceans all
destroy habitats, kill off organisms, and
reduce biodiversity.
II. Greenhouse Effect has forced many
species adapted to colder environments to
retreat further north. Arctic species may go
extinct from a loss of their habitat.
Human Impact on Biodiversity
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III. Human Expansion – Humans have an
average ecological footprint (Grade 7) that
is too large for the Earth to sustain. This
means ecosystems are suffering. Also, the
human population will reach 7 billion soon.
Our population explosion means increased
use of natural resources, clear-cutting and
urban sprawl. (e.g. Amazon Rain Forest)
Bioindicator Species
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A species that is an indicator of the overall
health of an ecosystem. These species
usually are large carnivores.
Why carnivores? Because when an
ecosystem suffers, carnivores are usually
the first to feel it, having trouble obtaining
food.
How Long Have Humans Been
Reducing Biodiversity?
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30000 years ago Early Homo Sapiens wiped out
our human competitors the Neanderthals.
8000 y.a. Humans wiped out the Wooly Mammoth
and other large mammals for food.
400 y.a. Portuguese sailors killed off the Dodo
bird for food.
Despite our long history, the rate of humancaused extinction is growing now at a faster rate
because of our technologies.
Extinction Versus Extirpation
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Extinction is the wiping out of an entire
species throughout the world
Extirpation is the wiping out of an entire
population of a species from an ecosystem
or area.