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Env sci lecture5

Env sci lecture5



How ecosystems work.

How ecosystems work.



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    Env sci lecture5 Env sci lecture5 Presentation Transcript

    • Chapter 5How Ecosystems Work
    • Lake Victoria Freshwater lake in Africa Formerly home to ≈ 400 species of cichlids 1960: Nile perch introduced 1990: water hyacinth invaded Today, ecological imbalance; why?
    • What Is Ecology? Literally study of one’s “house” Interactions Two components  Biotic  Abiotic Broadest biological field of study
    • Ecological Organization Organism Population Community Ecosystem Landscape Biosphere
    • Goals Of Ecologists Understand how ecosystems function Make connections: landscape ecology  Connections among ecosystems  Great blue heron
    • Energy Capacity or ability to do work Flows through ecosystems Why do organisms need energy? Different kinds Potential energy Kinetic energy
    • First Law of Thermodynamics Energy cannot be created or destroyed Energy can be changed from one form to another
    • Second Law of Thermodynamics When energy is changed from one form to another, some is degraded into heat Heat is a less usable form of energy Increases entropy in the universe
    • Ecosystem Composition Producers Consumers Decomposers
    • Producers Make their own food Photosynthesis Examples? Lii L gh gh tt e enne errg gyy 6CO2 + 6H2O + ------> C6H12O6 + 6O2
    • Consumers Feed on other things Herbivores Carnivores Omnivores Detrivores
    • Decomposers Break down dead organisms and waste products Examples?
    • Energy Flow Energy passes from one organism to the next Trophic level: each step in this flow of energy Food chain: straight path Food web  Interconnected food chains  More realistic than food chain; why?
    • Food Chain
    • FoodWeb
    • Biogeochemical Cycles Matter cycles through ecosystems Five cycles  Carbon  Hydrologic (water)  Nitrogen  Sulfur  Phosphorus
    • Carbon Cycle Essential component for life Gas (CO2) in atmosphere Several forms in ocean Can take a long time—think fossil fuels Photosynthesis Cellular respirationCO2 Sugar CO2
    • Carbon Cycle
    • Hydrologic CycleOcean Atmosphere Land Ocean
    • Nitrogen Cycle Proteins, DNA Atmosphere is 78% N2 Five steps  Nitrogen fixation  Nitrification  Assimilation  Ammonification  Denitrification
    • Nitrogen Fixation Specialized bacteria Split atmospheric nitrogen and combine it with hydrogen
    • Nitrogen Cycle
    • Sulfur Cycle Underground sedimentary rocks and minerals Erosion releases compounds to ocean Volcanoes Essential component of proteins
    • Sulfur Cycle
    • Phosphorus Cycle No atmospheric component Phosphates used in DNA and ATP (chemical energy) Phosphates move through the food chainLand Organism Organism Land
    • Phosphorus Cycle
    • Ecological Niche Everything about an organism  Adaptations  Use of resources  Lifestyle  Habitat
    • Ecological Niche Two species cannot occupy the same niche: why? Resource partitioning  Reduces niche overlap  Reduces competition
    • Resource Partitioning At Work!
    • Species Interactions No species lives in complete isolation Symbiosis  Intimate relationship between members of at least 2 species  Mutualism, commensalism, parasitism  Result of coevolution Other interactions  Predation, competition
    • Mutualism Both species benefit
    • Commensalism One species benefits, other not affected
    • Parasitism Parasite benefits, host is “harmed” Ectoparasites & endoparasites
    • Species Interactions Predation: consumption of one species by another Coevolution: “arms race”
    • Avoiding Predators Mechanical defenses Social groups Camouflage Protective chemicals
    • Species Interactions Competition: two or more organisms attempting to use the same resource Intraspecific vs. interspecific
    • Keystone Species Crucial to maintenance of an ecosystem Loss affects many other species Examples? This idea is being challenged; why?
    • Case Study: Global Climate Change Atmospheric CO2 increased dramatically. Why? 10 warmest years have occurred since 1990  2005 warmest  1998 second warmest  2002 third warmest Earth’s temperatures may rise 1.8o – 4.0o C (3.2o – 7.2o F) by end of 21st century What could occur?
    • Case Study: Global Climate Change Kyoto Protocol – International climate change conference – Kyoto, Japan 1997  Highly developed countries to cut CO2 emissions ~ 5.2% by 2012 US Department of Energy  Automotive vehicles designed for better gas mileage  High efficiency wind turbines