Extinctions

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

Problems 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