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Extinction
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The dodo What makes species vulnerable to extinction?
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Passenger pigeon
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Passenger pigeon
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Allee Effect Some species have a minimum requirement for population size in order to successfully breed
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Characteristics that predispose species to becoming extinct 1. habitat overlap - the species occupy habitat that is desirable to humans and lose out in competition with humans for the habitat - tallgrass prairie species 2. human attention - species suffer because singled out by humans - either desired as food or fur and hunted heavily (passenger pigeon, dodo, northern elephant seal); or disliked by humans and killed as varmints (wolves, African wild dogs) 3. large home range requirements - animals needing large areas can’t find large enough areas in human dominated landscape - California condor 4. limited adaptability and resilience - salmon return to natal stream to reproduce; won’t go elsewhere
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Konza Prairie – Kansas
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African wild dog
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California Condor
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Coho salmon
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Salmon Life Cycle
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Coho Salmon support 137 species
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Worldwide Endangered Species
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Endangered tree species - worldwide
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Rare and Endangered Species in Japan
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Endangered species in Canada and the US – as of 1990’s
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Threatened and Endangered Species
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Threatened And Endangered Species in Illinois
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Four-toed salamander – found at Green Oaks
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Minimum Viable Population The smallest population for a species which can be expected to survive for a long time Many factors effect MVP – the study of those factors is often called Population Viability Analysis – or Population Vulnerability Analysis – or PVA
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Factors that make populations vulnerable to extinction Environmental fluctuations Catastrophes Demographic uncertainties Genetic problems Habitat fragmentation
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Environmental Fluctuations
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Kirtland’s Warbler
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Cheetah
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Habitat Fragmentation Fragmentation is the transformation of large expanse of habitat into a number of smaller patches of smaller total area isolated from each other by a matrix of habitat unlike the original
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Domesday Book – 1085-86
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Selection from the Domesday Book
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Factors that make populations vulnerable to extinction Environmental fluctuations Catastrophes Demographic uncertainties Genetic problems Habitat fragmentation
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Heath Hen – Extinction Vortex
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Minimum Viable Population Size Another definition - often defined as 95% probability of 100 year survival, but can also plan for longer survival (500 or 1000 years) MVP is usually determined by modeling
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Forces which may cause extinction 1) deterministic - something essential is removed (habitat loss) or something lethal is added (pollutant, disease, introduced species) - presumably we can act to minimize these risks
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Forces which may cause extinction 2) stochastic (random) - environmental, catastrophic, demographic and genetic - this is what we need to worry about and what is hardest to prevent environmental randomness effects resources and conditions and we can't do much about it catastrophic randomness - floods, fires, hurricanes, volcanoes - can't really prevent but can spread individuals around to minimize the impact demographic - just natural random variation in birth and death rates can lead to extinction genetic - lack of genetic variability can lead to problems of inbreeding and poor response to diseases and environmental change
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Grizzly Bear and 50/500 Rule
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MVP – 50/500 Rule?
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English Skylark
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