Download Extinctions

Extinctions
Loss of Biodiversity
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EXTINCTION - the disappearance of a
species
Extinctions have been occurring constantly
at a low 'background rate', usually matched
by the rate at which new species appear resulting in an overall increase in biodiversity
A world without extinction would be really
crowded!!
Estimates of Organisms
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Fossil record from Precambrian period
estimate total number of species on Earth at
500 million
Current numbers of names species is 1.5 – 2
million
Current estimates of total species ranges
between 3 – 30 million
Mass Extinctions
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There have been several major
extinctions since the beginning
of life 3.5 billion years ago
End of Ordovician (440 mya)
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2nd most devestating in Earth’s history
Effecting marine species
Probably due to glaciation
Source:http://www.palaeos.com/Paleozoic/Ordovician/Ordovician.htm
Late Devonian (365 mya)
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Effecting marine and terrestrial species
Possibly due to global cooling since many warm
water species were lost
Occurred over
500,000 -15 million
years
Source: http://www.palaeos.com/Paleozoic/Devonian/Devonian.2.htm
Late Permian (225 mya)
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Largest extinction
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estimated that as many as 95% of all marine
species were lost
Possible causes
continents merging to
form Pangea
 global warming caused
by volcanic eruptions
 glaciation
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Source: http://www.palaeos.org/Permian
Late Triassic (200 mya)
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¼ of terrestrial families
Possible causes
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Climate change
Increased rainfall
Loss of biodiversity
allowed dinosaurs to
exploit abandoned
niches
Source:http://images.google.com/imgres?imgurl=htt
p://upload.wikimedia.org/wikipedia/commons/thum
b/c/cd/Iguanodon1.jpg/250pxIguanodon1.jpg&imgrefurl=http://en.wikipedia.org/
wiki/The_Crystal_Palace_Dinosaurs&h=186&w=25
0&sz=9&hl=en&start=29&tbnid=68NenapFjPWS7
M:&tbnh=83&tbnw=111&prev=/images%3Fq%3D
Labyrinthodon%26start%3D20%26gbv%3D2%26nd
sp%3D20%26hl%3Den%26sa%3DN
Cretaceous-Tertiary (65 mya)
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Effecting ½ of all marine species
Terrestrial plants, dinosaurs, and reptiles
became extinct.
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Gave rise to mammals
Possible causes:
 Impact hypothesis –
comet collided with
the earth
Source:
http://www.worldbook.com/wb/Students?content_spotlight/dinosaurs/world_mesozoic
Pleistocene (11, 000 ya)
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Ice age period
Loss of 75% of large genus (mammals)
Possible causes
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Hunting
Climate change
Disease
Source: http://www.msnbc.msn.com/id/12721432/
Recent Extinction Rates
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11,000 – 400 ya
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400 – 100 ya
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1% of species per decade
1% of birds and mammals
Approximately 1% per decade
Presently
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1% per day
Recent Extinction Rates
continued
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The ratio of 1600:present = 1:10
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Much faster than natural
By the year 2010 over 500,000 species of
plants and animals will have become extinct
since the Pleistocene
Past causes of extinction
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Climate change
Volcanic events
Magnetic reversal of the poles
Sea level changes
Collision of Meteorites
Glaciations
Plate tectonics
Competition / predation
Present causes of
extinction/loss of biodiversity 
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Mostly human impact
HIPPO
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Habitat destruction
Introduced species
Pollution
Population
Over consumption
Habitat destruction
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Degradation
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Fragmentation
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e.g. stream siltation caused by
deforestation
e.g.highways through national parks
Loss
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e.g. new strip mall on Hanes Mall Blvd
Introduced species
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Non-native species
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e.g. green crab, zebra mussel,
ctenophore in Mediterranean Sea
Genetically modified species
Pollution
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Air
Water
Land
Major sources:
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Fossil fuels
Domestic waste
Industrial waste
Manufacturing processes
Agriculture
Population
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With the global population increasing at
a rate of 3 people per second there is:
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Increasing use of resources
Increasing habitat destruction
Increasing waste production
Over consumption
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Hunting, collecting, harvesting
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e.g. Atlantic cod for food
e.g. sea otter for fur
Wildlife trade e.g. bear gallbladders as
aphrodisiacs
Indirectly through over consumption of
resources e.g. water, land
Problems
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Don’t know total number of species on
planet
Difficult to quantify the relationship
between man’s impact and species loss
Difficult to quantify the relationship
between mans impact and habitat loss