1 / 20

Extinctions and Loss of Biodiversity: Past, Present, and Future Impacts

Explore the history of extinctions, from the Ordovician to the Pleistocene, and the current crisis of biodiversity loss driven by human impacts like habitat destruction, pollution, and overconsumption.

hectorparson
Télécharger la présentation

Extinctions and Loss of Biodiversity: Past, Present, and Future Impacts

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Extinctions

  2. 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!!

  3. 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

  4. Mass Extinctions • There have been several major extinctions since the beginning of life 3.5 billion years ago

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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 earth Source: http://www.worldbook.com/wb/Students?content_spotlight/dinosaurs/world_mesozoic

  10. 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/

  11. 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

  12. 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

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

  14. Present causes of extinction/loss of biodiversity - • Mostly human impact • HIPPO • Habitat destruction • Introduced species • Pollution • Population • Over consumption

  15. 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

  16. Introduced species • Non-native species • e.g. green crab, zebra mussel, ctenophore in Mediterranean Sea • Genetically modified species

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

  18. 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

  19. 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

  20. 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

More Related