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Chapter 5 How 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 Positive and Negative Feedback Loops Feedback Loop circular process Positive Feedback Loop change becomes more pronounced Negative Feedback Loop change is reduced or inhibited Landscape Ecology Studies the connections among ecosystems Ecosystem engineers Organisms that create or modify habitat How are grizzly bears ecosystem engineers? Goals Of Ecologists Understand how ecosystems function Make connections: landscape ecology Connections among ecosystems Grizzly Bears 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? 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 Biological Production Net Primary Production: amount of plant mass generated by photosynthesis and that remains after cellular respiration Biomass: total amount of organic matter NPP is measured by tracking the changes in biomass over time (NPP = B2 –B1) Food Web 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 CO2 Cellular respiration Sugar CO2 Carbon Cycle Hydrologic Cycle Ocean 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 Phosphorus Cycle No atmospheric component Phosphates used in DNA and ATP (chemical energy) Phosphates move through the food chain Land 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? What are the differences between a keystone, umbrella or flagship species? Adaptive Ecosystem Management Ecosystem Management: meeting the goals or objectives of the biotic community and their associated abiotic components Adaptive Ecosystem Management: developed by C.S. Holling and Carl J. Walters, University of B.C., 1970 acknowledges the uncertainty and the need for managers to learn while they manage passive and active Eco Canada Career Focus Consider a career as an ecologist Ecologists study the relationships between living things and their environments Case Study: Human Appropriation of Net Primary Productivity (HANPP) HANPP : indicator of are of land an the amount of biomass consumed by humans Valuable indicator of “human domination of ecosystems” on a global scale Many countries are consuming an excess of 100% of locally available NPP Case Study: Human Appropriation of Net Primary Productivity (HANPP)