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 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 Two Important Laws First law of thermodynamics Energy cannot be created or destroyed Energy can be changed from one form to another Two Important Laws 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 Food Web Biogeochemical Cycles Matter cycles through ecosystems Four cycles Hydrologic (water) Carbon Nitrogen Phosphorus Hydrologic Cycle Ocean Atmosphere Land Ocean 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 Nitrogen Cycle Proteins, DNA Atmosphere is 78% N2 Five steps 1) Nitrogen fixation 2) Nitrification 3) Assimilation 4) Ammonification 5) Denitrification Nitrogen Fixation Specialized bacteria Split atmospheric nitrogen and combine it with hydrogen Roots of a pea plant Nostoc Nitrogen Cycle Nitrification: ammonia converted to nitrate Assimilation: plants or animals taking in nitrates Ammonification: organisms produce nitrogen-containing wastes Denitrification: nitrate converted back to nitrogen gas Different bacteria perform these steps 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? This idea is being challenged; why? Case Study: Global Warming Greenhouse effect Natural effect Occurs when greenhouse gases trap heat in the atmosphere Without the greenhouse effect, earth would be much colder CO2 is a major greenhouse gas Where is it coming from? Case Study: Global Warming What should be done? Kyoto Protocol Developed countries must cut greenhouse gas emissions What did the U.S. do? Other solutions?