Transcript Extinctions
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=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) 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 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 400 – 100 ya 1% of species per decade 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 Fragmentation e.g. stream siltation caused by deforestation 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