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Extinctions

Extinctions. Estimates of Organisms. Fossil records from the Precambrian period estimate the total number of species on Earth to be 500 million The current numbers of known species is between 1.5 – 2 million Current estimates of total species ranges between 10 – 100 million.

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Extinctions

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  1. Extinctions

  2. Estimates of Organisms • Fossil records from the Precambrian period estimate the total number of species on Earth to be 500 million • The current numbers of known species is between 1.5 – 2 million • Current estimates of total species ranges between 10 – 100 million

  3. 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 • A world without extinction would be really crowded!!

  4. Mass Extinction • Sudden loss of many species in a short time • Mass extinctions are usually attributed to a rapid climate change, a meteorite impact, or a large volcanic explosion.

  5. Mass Extinctions • There have been five major extinctions since the beginning of life on Earth 4.6 billion years ago

  6. Look for the mass extinctions on the fossil record.

  7. 1: Late Ordovician (440 mya) • 2nd most devastating in Earth’s history • 25% of all families were lost • Probably due to glaciation and sea level changes Source:http://www.palaeos.com/Paleozoic/Ordovician/Ordovician.htm

  8. 2. Devonian (365 mya) • Effecting marine and terrestrial species • Possibly due to global cooling since many warm water species were lost • Occurred over a span of 500,000 -15 million years Source: http://www.palaeos.com/Paleozoic/Devonian/Devonian.2.htm

  9. 3. Permian -Triassic (250 mya) • Largest extinction • estimated that as many as 95% of all marine species were lost • 54% of all families were lost • Possible causes • continents merging to form Pangaea • global cooling caused by volcanic eruptions • Ice age may have followed Source: http://www.palaeos.org/Permian

  10. 4. Late Triassic (200 mya) • 23% of all terrestrial families • Possible causes • Climate change as Pangeae broke apart

  11. 5. Cretaceous-Tertiary (65 mya) • Also known as the K-T extinction • Effecting ½ of all marine species • Many terrestrial plants, dinosaurs, and reptiles became extinct. • Gave rise to mammals Source: http://www.worldbook.com/wb/Students?content_spotlight/dinosaurs/world_mesozoic

  12. 5. K – T Extinction Continued • Possible causes: • Impact hypothesis – meteor collided with the Earth on the Yucatan in Mexico and/or eruption of volcanoes in the Deccan Plateau in India, causing dust clouds, stopping photosynthesis

  13. 6. Pleistocene (11,000 ya) • Start of the 6th extinction event (Holocene) • Ice age period • Loss of 75% of large genus (mammals) • Possible causes • Hunting • Climate change Source: http://www.msnbc.msn.com/id/12721432/

  14. 6. Holocene extinction event • The 6th and current mass extinction. • Started at the end of the last ice age 10,000 years ago with the extinction of the large mammals. • The rate of extinction has increased in the past 100 years.

  15. Background Extinction Rate • The natural extinction rate of all species over time • Current estimates 1 species per million species per year. • Determine the background extinction rate given the current estimate of 10-100 million species:

  16. Current Extinction Rates • 10 – 100 species per year – Did you get this? • Some experts estimate that the current extinction rate is 1000 times the background extinction rate • According to E.O. Wilson: 3 extinct species per hour

  17. Recent Extinction Rates continued • By the year 2010 over 500,000 species of plants and animals will have become extinct since the Pleistocene period. • The current rate of extinction is caused by one species: Humans!

  18. Past causes of extinction • Climate change • Volcanic events • Magnetic reversal of the poles • Sea level changes • Collision of Meteorites • Glaciations • Plate tectonics • Competition / predation

  19. Present causes of extinction/loss of biodiversity - • Human Impact • HIPPO • Habitat destruction • Introduced species = invasive species • Pollution • Population • Over exploitation

  20. Habitat destruction • Degradation • e.g. stream siltation caused by deforestation • Fragmentation • e.g.highways through national parks • Loss of habitat • e.g. new strip mall, vineyards, new housing development

  21. Introduced species (invasive) • Non-native species • e.g. green crab, zebra mussel, salmon in Chile • Genetically modified species that invade natural areas.

  22. Pollution • Air • Water • Land • Major sources: • Fossil fuels • Domestic waste • Industrial waste • Manufacturing processes • Agriculture

  23. Population • The global population is increasing at a rate of 3 people per second: • Increasing use of resources • Increasing habitat destruction • Increasing waste production and pollution

  24. Over exploitation • Hunting, collecting, harvesting • e.g. Atlantic cod for food (over fishing) • e.g. sea otter for fur • Wildlife trade e.g. bear gallbladders as aphrodisiacs • Indirectly through consumption of resources e.g. water, land

  25. Resources: • Course Companion • Text by Miller

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