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Today –finish biodiversity (Chapter 23) –start conservation biology (Chapter 25) Wednesday –conservation biology Friday –quiz! –conservation biology Monday

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  • Today finish biodiversity (Chapter 23) start conservation biology (Chapter 25) Wednesday conservation biology Friday quiz! conservation biology Monday historical biogeography (Chapter 24) Wednesday ecosystem management (outside reading)
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  • Conservation Biology - a mission- oriented science that focuses on protecting and restoring biodiversity Biodiversity 1.All forms of life 2.All levels of organization (subpopulation to biosphere) 3.All interactions among forms of life and the environment
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  • Where is the biodiversity? Endemic species restricted to a small region isolated areas (islands, mountain ranges) product of unique habitat, climate features
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  • Biodiversity hotspots - areas with a high concentration of endemic species, experiencing rapid habitat loss
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  • Hotspots: 1.4% of the land area 44% of vascular plant species 35% of terrestrial vertebrate species But 20% of the human population, which is growing at 1.8% per year (vs. 1.3% worldwide) each hotspot has already lost 70% of its vegetation
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  • Current Status of Biodiversity 1.4 million described species, possibly 10 million in total Background extinction rate rate of species loss in the absence of human activities fossil record: species survive 1-10 million years one year: one species has a 1 in 1-10 million chance of going extinct total: 1 extinction per year
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  • Mass extinction loss of large number of species usually due to catastrophic volcano or meteor impact very rare (5 times in 3 billion years) Current rate of extinction???
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  • Some estimates for current rate: 1 species per hour 1 million species total, so far 10% of all species so far 8.8% of all species 27,000 species per year 20% of neotropical plant species 100 to 10,000 times the background rate
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  • Numbers of threatened/endagered species: 5,188 vertebrates (9%) 1,992 invertebrates (0.17%) 8,321 plants (2.89%) 2 lichens (0.02%) Since 1600, ~1000 species have gone extinct (probably many more)
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  • Why do species go extinct? 2 separate processes: 1.Something causes a large population to decline. 2.Small populations go extinct.
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  • Causes of species declines 1.Habitat destruction and fragmentation 2.Introduced species 3.Exploitation and overharvesting 4.Pollution 5.Climate change
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  • USA
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  • 1.Habitat destruction and fragmentation Fragmentation disruption of extensive habitats into small, isolated patches
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  • Relaxation loss of species from isolated habitats over time Area S
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  • Edge effects negative impacts adjacent to habitat boundaries Forest edges: more sunlight drying high winds tree mortality invasive species more predators
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  • Core area Edge area Core area part of a patch not impacted by edge effects Patch size is not always the best predictor of patch quality
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  • 2.Introduced species Humans are constantly moving species between continents, islands deliberate or accidental Most serious impacts on islands low species diversity few native predators animals lack anti-predator defenses, resistance to diseases
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  • Characteristics of invasive species pioneer species high dispersal rates found in disturbed habitats, but some can invade undisturbed communities Why are invasives successful? no diseases, herbivores, parasites, predators better competitors than native species
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  • Introduced diseases exploit lack of evolved resistance Dutch elm disease American elm Chestnut blight American chestnut avian malaria Hawaiian birds Rinderpest African ungulates chytrid fungus amphibians
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  • Net result of invasive species homogenize ecological communities around the world drive native, endemic species extinct
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  • 3.Exploitation and overharvest Direct exploitation for food overfishing bycatch in fisheries killing non-target species (birds, marine mammals) bush meat harvest of wild animals for food can be sustainable, but often not threatens many large mammals, primates
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  • Global trade in wildlife birds, orchids, cactus, primates captured for gardens, pets, zoos, etc. Many species driven extinct before hunting/harvest regulations were in place passenger pigeon, island tortoises, marine mammals
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  • Exam Definitions, compare-contrast 5 points each (20 points per page) 5 questions 12 points per question bonuses 3 points each dropped the question with the lowest score Average grade = 86
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  • Causes of species declines 1.Habitat destruction and fragmentation 2.Introduced species 3.Exploitation and overharvesting 4.Pollution 5.Climate change
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  • 4.Pollution Most important for aquatic systems chemical pollutants acid precipitation Bioaccumulation process by which toxin concentrations increase in living tissues concentrations increase through the food chain
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  • 5.Climate change
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  • Why do small populations go extinct? Demographic stochasticity chance events that occur at small populations size failure to breed or survive failure to find a mate skewed sex ratio
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  • Dusky Seaside Sparrow
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  • Environmental effects unpredictable events that reduce survival or reproduction droughts, floods, fires, storms Genetic effects at small population size inbreeding genetic drift random mutations
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  • Extinction vortex combination of genetic, environmental and demographic factors that drive a small population to extinction
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  • Heath hen 1700 throughout the northeast coast 1907 50 left on Marthas Vineyard 1915 2000 birds 1916 fire 1917 goshawk invasion 1920s poultry disease 1927 13 birds, mostly males March 11, 1932 last known sighting
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  • Minimum viable population smallest population has a specified probability of surviving for a certain time usually 95% chance of surviving for 100 years How big? at least 50 individuals to avoid demographic stochasticity at least 500 individuals to avoid genetic effects realistically > 1000 but varies by species
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  • Reasons for protecting biodiversity 1.Intrinsic valuable for its own sake 2.Instrumental beneficial to humans
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  • Instrumental Reasons for Protecting Biodiversity 1.Economic benefits food drugs cultivated crops ecotourism
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  • 2.Ecosystem services quantifiable services that an ecosystem provides to humans often very valuable economically Examples: moderating climates mitigating floods and droughts eliminating waste and toxins pest control pollination
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  • Pollinators Insects pollinate 2/3 of crop species ~25% of foods consumed U.S.: $20 to 40 billion in agriculture Evidence that many pollinators are declining bats honeybees hummingbirds
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  • 3.Maintenance of ecosystem function How many species can you safely remove? How do you ensure maximum productivity in managed or natural ecosystems?
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  • More diverse ecosystems are more stable
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  • Diversity-productivity relationship How are plant species richness and primary productivity related? 3 possibilities:
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  • Why would productivity increase with richness? Greater odds of encountering a super- productive species Complementarity use of different resources by different species
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