extinctions. loss of biodiversity extinction - the disappearance of a species extinctions have been...
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Loss of Biodiversity 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 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 There have been several major
extinctions since the beginning of life 3.5 billion years ago
End of Ordovician (440 mya) 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) 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) Largest extinction
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
Source: http://www.palaeos.org/Permian
Late Triassic (200 mya) ¼ of terrestrial families Possible causes
Climate change Increased rainfall
Loss of biodiversity
allowed dinosaurs to
exploit abandoned
niches
Source:http://images.google.com/imgres?imgurl=http://upload.wikimedia.org/wikipedia/commons/thumb/c/cd/Iguanodon1.jpg/250px-Iguanodon1.jpg&imgrefurl=http://en.wikipedia.org/wiki/The_Crystal_Palace_Dinosaurs&h=186&w=250&sz=9&hl=en&start=29&tbnid=68NenapFjPWS7M:&tbnh=83&tbnw=111&prev=/images%3Fq%3DLabyrinthodon%26start%3D20%26gbv%3D2%26ndsp%3D20%26hl%3Den%26sa%3DN
Cretaceous-Tertiary (65 mya) Effecting ½ of all marine species Terrestrial plants, dinosaurs, and reptiles
became extinct. Gave rise to mammals
Possible causes: Impact hypothesis –
comet collided with
the earthSource: http://www.worldbook.com/wb/Students?content_spotlight/dinosaurs/world_mesozoic
Pleistocene (11, 000 ya) Ice age period Loss of 75% of large genus (mammals) Possible causes
Hunting Climate change Disease
Source: http://www.msnbc.msn.com/id/12721432/
Recent Extinction Rates 11,000 – 400 ya
1% of species per decade
400 – 100 ya 1% of birds and mammals Approximately 1% per decade
Presently 1% per day
Recent Extinction Rates continued
The ratio of 1600:present = 1:10 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 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 - Mostly human impact HIPPO
Habitat destruction Introduced species Pollution Population Over consumption
Habitat destruction Degradation
e.g. stream siltation caused by deforestation
Fragmentation e.g.highways through national parks
Loss e.g. new strip mall on Hanes Mall Blvd
Introduced species Non-native species
e.g. green crab, zebra mussel, ctenophore in Mediterranean Sea
Genetically modified species
Pollution Air Water Land Major sources:
Fossil fuels Domestic waste Industrial waste Manufacturing processes Agriculture
Population With the global population increasing at
a rate of 3 people per second there is: Increasing use of resources Increasing habitat destruction Increasing waste production
Over consumption Hunting, collecting, harvesting
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