Ecosystems: What are they and how do they work? Ecosystems: What are they and how do they work? Chapter 3 Miller’s Living in the Environment 16th Edition.

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  • Ecosystems: What are they and how do they work?Chapter 3Millers Living in the Environment16th Edition

  • Ecology and LifeEcology- study of relationships between organisms and their environmentEcology examines how organisms interact with their nonliving (abiotic) environment such as sunlight, temperature, moisture, and vital nutrientsBiotic interaction among organisms, populations, communities, ecosystems, and the ecosphere

  • Connections with naturePopulationGroup of interacting individuals of the same species that occupy a specific area at the same timeGenetic DiversityPopulations that are dynamic groups that change in size, age distribution, density, and genetic composition as a result of changes in environmental conditions

  • Habitat Place where a population or individual organism naturally livesCommunity Complex interacting network of plants, animals, and microorganismsEcosystem Community of different species interacting with one another and with their nonliving environment of matter and energyEcosphere or Biosphere All earth's ecosystems


  • AtmosphereThin envelope of air around the planetTroposphereextends about 17 kilometers above sea level, contains nitrogen (78%), oxygen(21%), and is where weather occursStratosphere17-48 kilometers above sea level, lower portions contains enough ozone (O3) to filter out most of the suns ultraviolet radiation

  • SunFireball of hydrogen (72%) and helium (28%)Nuclear fusionSun has existed for 6 billion yearsSun will stay for another 6.5 billion yearsVisible light that reaches troposphere is the ultraviolet ray which is not absorbed in ozone

  • Solar Energy

    72% of solar energy warms the lands0.023% of solar energy is captured by green plants and bacteriaPowers the cycling of matter and weather systemDistributes heat and fresh water

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  • Geosphere

  • Geosphere

  • Hydrosphere

    Consists of the earths liquid water, ice, and water vapor in the atmosphere

  • What is Life?All life shares a set of basic characteristics Made of cells that have highly organized internal structure and functionsCharacteristic types of deoxyribonucleic acid (DNA) molecules in each cell

  • Biomes Large regions characterized by distinct climate, and specific life-formsClimate Long-term weather; main factor determining what type of life will be in a certain area.

  • Type of NutrientsNutrient Any atom, ion, or molecule an organism needs to live grow or reproduceEx: carbon, oxygen, hydrogen, nitrogen etcMacronutrient nutrient that organisms need in large amountEx: phosphorus, sulfur, calcium, iron etcMicronutrient nutrient that organism need in small amountEx: zinc, sodium, copper etc

  • Ecosphere SeparationThe Ecosphere and its ecosystem can be separated into two partsAbiotic- nonliving, componentsEx: air, water, solar energyPhysical and chemical factors that influence living organismsBiotic- living, components Ex: plants and animals

  • Range of ToleranceVariations in its physical and chemical environmentDifferences in genetic makeup, health, and age.Ex: trout has to live in colder water than bass

  • Limiting FactorMore important than others in regulating population growthEx: water light, and soilLacking water in the desert can limit the growth of plants

  • Limiting Factor Principletoo much or too little of any abiotic factor can limit growth of population, even if all the other factors are at optimum (favorable) range of tolerance.Ex: If a farmer plants corn in phosphorus-poor soil, even if water, nitrogen are in a optimum levels, corn will stop growing, after it uses up available phosphorus.

  • Dissolved Oxygen ContentAmount of oxygen gas dissolved in a given volume of water at a particular temperature and pressure.Limiting factor of aquatic ecosystem

  • Salinityamount of salt dissolved in given volume of water

  • Living Organisms in EcosystemProducers or autotrophs- makes their own food from compound obtained from environment.Ex: plant gets energy or food from sun

  • PhotosynthesisProducer transmit 1-5% of absorbed energy into chemical energy, which is stored in complex carbohydrates, lipids, proteins and nucleic acid in plant tissue

  • Chemosynthesis-Bacteria can convert simple compounds from their environment into more complex nutrient compound without sunlightEx: becomes consumed by tubeworms, clams, crabsBacteria can survive in great amount of heat

  • Consumers or HeterotrophsObtain energy and nutrients by feeding on other organisms or their remains

  • ConsumersHerbivores (plant-eaters) or primary consumersFeed directly on producersDeer, goats, rabbits

  • ConsumersCarnivores (meat eater) or secondary consumersFeed only on primary consumerLion, Tiger

  • ConsumersTertiary (higher-level) consumer Feed only on other carnivoresWolf

  • ConsumersOmnivores- consumers that eat both plants and animalsEx: pigs, humans, bears

  • ConsumersScavengers- feed on dead organismsVultures, flies, crows, shark

  • ConsumersDetritivores- live off detritusDetritus parts of dead organisms and wastes of living organisms.Detritus feeders- extract nutrients from partly decomposed organic matter plant debris, and animal dung.

  • ConsumersDecomposers - Fungi and bacteria break down and recycle organic materials from organisms wastes and from dead organisms Food sources for worms and insectsBiodegradable - can be broken down by decomposers

  • RespirationAerobic Respiration Uses oxygen to convert organic nutrients back into carbon dioxide and waterGlucose + oxygen Carbon dioxide + water + energyAnaerobic Respiration or FermentationBreakdown of glucose in absence of oxygen

  • Food ChainFood Chain-Series of organisms in which each eats or decomposes the preceding oneDecomposers complete the cycle of matter by breaking down organic waste, dead animal. Plant litter and garbage. Whether dead or alive organisms are potential (standard) sources of food for other organisms.

  • Food WebComplex network of interconnected food chainsFood web and chains One-way flow of energyCycling of nutrients through ecosystem

  • Food WebsGrazing Food WebsEnergy and nutrients move from plants to herbivoresThen through an array of carnivoresEventually to decomposers(100,000 Units of Energy)

  • Food WebsGrazing Food WebsEnergy and nutrients move from plants to herbivoresThen through an array of carnivoresEventually to decomposers(1,000 Units of Energy)

  • Second Law of EnergyOrganisms need high quality chemical energy to move, grow and reproduce, and this energy is converted into low-quality heat that flows into environmentTrophic levels or feeding levels- Producer is a first trophic level, primary consumer is second trophic level, secondary consumer is third.Decomposers process detritus from all trophic levels.

  • Food WebsGrazing Food WebsEnergy and nutrients move from plants to herbivoresThen through an array of carnivoresEventually to decomposers(100 Units of Energy)

  • Food WebsGrazing Food WebsEnergy and nutrients move from plants to herbivoresThen through an array of carnivoresEventually to decomposers(1 Units of Energy)

  • Food WebsGrazing Food WebsEnergy and nutrients move from plants to herbivoresThen through an array of carnivoresEventually to decomposers(10 Units of Energy)

  • Food WebsDetrital Food WebsOrganic waste material or detritus is the major food sourceEnergy flows mainly from producers (plants) to decomposers and detritivores.

  • Pyramid of Energy FlowMore steps or trophic levels in food chain or web, greater loss of usable energy as energy flows through trophic levelsMore trophic levels the Chains or Webs have more energy is consumed after each one. Thats why food chains and webs rarely have more than 4 steps

  • Distinction between SpeciesWild species- one that exists as a population of individuals in a natural habitat, ideally similar to the one in which its ancestors evolved

    Domesticated species- animals such as cows, sheep, food crops, animals in zoos

  • Living OrganismsCapture and transform matter and energy from their environment to supply their needs for survival, growth, and reproductionMaintain favorable internal conditions, despite changes in their external environment through homeostasis, if not overstressed

  • BiomassDry weight of all organic matter contained in organisms.Biomass is measured in dry weight Water is not source of energy or nutrient Biomass of first trophic levels is dry mass of all producersUseable energy transferred as biomass varies from 5%-20% (10% standard)

  • Pyramid of BiomassStorage of biomass at various trophic levels of ecosystem

  • Pyramid of Energy FlowLoss of usable energy as energy flows through trophic levels of food chains and webs Rarely have more than 4 steps

  • Pyramid of NumbersNumber of organisms at each trophic level


  • Gross Primary Productivity (GPP)Rate in which producers convert solar energy into chemical energy (biomass) in a given amount of time

  • Net Primary Productivity (NPP)Rate in which energy for use by consumers is stored in new biomass of plantsMeasured in kilocalories per square meter per year or grams in biomassNPP is the limit determining the planets carrying capacity for all species.59% of NPP occurs in land / 41% occurs in ocean

  • Nutrient Cycles and Soils

  • Matter Cycling in EcosystemsNutrient or Biogeochemical CyclesNatural processes that recycle nutrients in various chemical forms in a cyclic manner from the nonliving environment to living organisms and back again

  • Nutrient Cycling & Ecosystem Sustainability Natural ecosystems tend to balanceNutrients are recycled with reasonable efficiencyHumans are accelerating rates of flow of materNutrient loss from soilsDoubling of normal flow of nitrogen in the nitrogen cycle is a contributes to global warming, ozone depletion, air pollution, and loss of biodiversityIsolated ecosystems are being influenced by human activities

  • Nutrient Cycles (Closed System) Energy Flow (Open System)WaterCarbonNitrogenPhosphorus

    SulfurRockSoilEnergy Flow

  • Biogeochemical Cycle LocationsHydrosphereWater in the form of ice, liquid, and vaporOperates local, regional, and global levelsAtmosphericLarge portion of a given element (i.e. Nitrogen gas) exists in gaseous form in the atmosphereOperates local, regional, and global levelsSedimentaryThe element does not have a gaseous phase or its gaseous compounds dont make up a significant portion of its supplyOperates local and regional basis

  • Ecological EfficiencyPercentage of energy transferred from one trophic level to another.10% ecological efficiency 1,000,000 units of energy from sun10,000 units available for green plants (photosynthesis)1000 units for herbivores100 units for primary carnivores10 units for secondary carnivores

  • Ecosystem ImportanceEcosystem services are the natural services or earth capital that support life on the earth Essential to the quality of human life and to the functioning of the worlds economies

  • Ecosystem ImportanceEcosystem services include: Controlling and moderating climateProviding and renewing air, water, soilRecycling vital nutrients through chemical cyclingProviding renewable and nonrenewable energy sources and nonrenewable mineralsFurnishing people with food, fiber, medicines, timber, and paper

  • Ecosystem ImportanceEcosystem services includePollinating crops and other plant speciesAbsorbing, diluting, and detoxifying many pollutants and toxic chemicalsHelping control populations of pests and disease organismsSlowing erosion and preventing floodingProviding biodiversity of genes and species

  • Two Principles of Ecosystem SustainabilityUse renewable solar energy as energy sourceEfficiently recycle nutrients organisms need for survival, growth, and reproduction

  • Studying EcosystemsFIELD RESEARCHGoing into nature and observing/measuring the structure of ecosystemsMajority of what we know now comes from this typeDisadvantage is that it is expensive, time-consuming, and difficult to carry out experiments due to many variablesLABORATORY RESEARCHSet up, observation, and measurement of model ecosystems under laboratory conditions Conditions can easily be controlled and are quick and cheapDisadvantage is that it is never certain whether or not result in a laboratory will be the same as a result in a complex, natural ecosystemSYSTEMS ANALYSISSimulation of ecosystem rather than study real ecosystemHelps understand large and very complicated systems



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