Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 54 Ecosystems
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings. Overview: Ecosystems, Energy, and Matter An ecosystem consists of all the organisms living in a community – As well as all the abiotic factors with which they interact
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings. Ecosystems can range from a microcosm, such as an aquarium – To a large area such as a lake or forest Figure 54.1
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings. Regardless of an ecosystem’s size – Its dynamics involve two main processes: energy flow and chemical cycling Energy flows through ecosystems – While matter cycles within them
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ecosystems and Physical Laws The laws of physics and chemistry apply to ecosystems – Particularly in regard to the flow of energy Energy is conserved – But degraded to heat during ecosystem processes
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Trophic Relationships Energy flows through an ecosystem – Entering as light and exiting as heat Figure 54.2 Microorganisms and other detritivores Detritus Primary producers Primary consumers Secondary consumers Tertiary consumers Heat Sun Key Chemical cycling Energy flow
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings. Detritivores, mainly bacteria and fungi, recycle essential chemical elements – By decomposing organic material and returning elements to inorganic reservoirs Figure 54.3
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings. Concept 54.2: Physical and chemical factors limit primary production in ecosystems Primary production in an ecosystem – Is the amount of light energy converted to chemical energy by autotrophs during a given time period
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ecosystem Energy Budgets The extent of photosynthetic production – Sets the spending limit for the energy budget of the entire ecosystem
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Gross and Net Primary Production Total primary production in an ecosystem – Is known as that ecosystem’s gross primary production (GPP) Not all of this production – Is stored as organic material in the growing plants
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings. Net primary production (NPP) – Is equal to GPP minus the energy used by the primary producers for respiration Only NPP – Is available to consumers
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings. Overall, terrestrial ecosystems – Contribute about two-thirds of global NPP and marine ecosystems about one-third Figure 120 W 60 W 00 60 E120 E 180 North Pole 60 N 30 N Equator 30 S 60 S South Pole
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Eutrophication In some areas, sewage runoff – Has caused eutrophication of lakes, which can lead to the eventual loss of most fish species from the lakes Figure 54.7
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings. Concept 54.3: Energy transfer between trophic levels is usually less than 20% efficient The secondary production of an ecosystem – Is the amount of chemical energy in consumers’ food that is converted to their own new biomass during a given period of time
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Production Efficiency When a caterpillar feeds on a plant leaf – Only about one-sixth of the energy in the leaf is used for secondary production Figure Plant material eaten by caterpillar Cellular respiration Growth (new biomass) Feces 100 J 33 J 200 J 67 J
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Pyramids of Production This loss of energy with each transfer in a food chain – Can be represented by a pyramid of net production Figure Tertiary consumers Secondary consumers Primary consumers Primary producers 1,000,000 J of sunlight 10 J 100 J 1,000 J 10,000 J
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings. Most biomass pyramids – Show a sharp decrease at successively higher trophic levels Figure 54.12a (a) Most biomass pyramids show a sharp decrease in biomass at successively higher trophic levels, as illustrated by data from a bog at Silver Springs, Florida. Trophic level Dry weight (g/m 2 ) Primary producers Tertiary consumers Secondary consumers Primary consumers
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings. Certain aquatic ecosystems – Have inverted biomass pyramids Figire 54.12b Trophic level Primary producers (phytoplankton) Primary consumers (zooplankton) (b) In some aquatic ecosystems, such as the English Channel, a small standing crop of primary producers (phytoplankton) supports a larger standing crop of primary consumers (zooplankton). Dry weight (g/m 2 ) 21 4
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Pyramids of Numbers A pyramid of numbers – Represents the number of individual organisms in each trophic level Figure Trophic level Number of individual organisms Primary producers Tertiary consumers Secondary consumers Primary consumers 3 354, ,624 5,842,424
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings. The dynamics of energy flow through ecosystems – Have important implications for the human population Eating meat – Is a relatively inefficient way of tapping photosynthetic production
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings. Worldwide agriculture could successfully feed many more people – If humans all fed more efficiently, eating only plant material Figure Trophic level Secondary consumers Primary consumers Primary producers
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A General Model of Chemical Cycling Gaseous forms of carbon, oxygen, sulfur, and nitrogen – Occur in the atmosphere and cycle globally Less mobile elements, including phosphorous, potassium, and calcium – Cycle on a more local level
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings. A general model of nutrient cycling – Includes the main reservoirs of elements and the processes that transfer elements between reservoirs Figure Organic materials available as nutrients Living organisms, detritus Organic materials unavailable as nutrients Coal, oil, peat Inorganic materials available as nutrients Inorganic materials unavailable as nutrients Atmosphere, soil, water Minerals in rocks Formation of sedimentary rock Weathering, erosion Respiration, decomposition, excretion Burning of fossil fuels Fossilization Reservoir aReservoir b Reservoir c Reservoir d Assimilation, photosynthesis
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Biogeochemical Cycles The water cycle and the carbon cycle Figure Transport over land Solar energy Net movement of water vapor by wind Precipitation over ocean Evaporation from ocean Evapotranspiration from land Precipitation over land Percolation through soil Runoff and groundwater CO 2 in atmosphere Photosynthesis Cellular respiration Burning of fossil fuels and wood Higher-level consumers Primary consumers Detritus Carbon compounds in water Decomposition THE WATER CYCLE THE CARBON CYCLE
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Water moves in a global cycle – Driven by solar energy The carbon cycle – Reflects the reciprocal processes of photosynthesis and cellular respiration
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The nitrogen cycle and the phosphorous cycle Figure N 2 in atmosphere Denitrifying bacteria Nitrifying bacteria Nitrifying bacteria Nitrification Nitrogen-fixing soil bacteria Nitrogen-fixing bacteria in root nodules of legumes Decomposers Ammonification Assimilation NH 3 NH 4 + NO 3 NO 2 Rain Plants Consumption Decomposition Geologic uplift Weathering of rocks Runoff Sedimentation Plant uptake of PO 4 3 Soil Leaching THE NITROGEN CYCLE THE PHOSPHORUS CYCLE
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Most of the nitrogen cycling in natural ecosystems – Involves local cycles between organisms and soil or water The phosphorus cycle – Is relatively localized
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Decomposition and Nutrient Cycling Rates Decomposers (detritivores) play a key role – In the general pattern of chemical cycling Figure Consumers Producers Nutrients available to producers Abiotic reservoir Geologic processes Decomposers
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings. Net losses of water and minerals were studied – And found to be greater than in an undisturbed area These results showed how human activity – Can affect ecosystems Figure 54.19c (c) The concentration of nitrate in runoff from the deforested watershed was 60 times greater than in a control (unlogged) watershed. Nitrate concentration in runoff (mg/L) Deforested Control Completion of tree cutting
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 54.5: The human population is disrupting chemical cycles throughout the biosphere As the human population has grown in size – Our activities have disrupted the trophic structure, energy flow, and chemical cycling of ecosystems in most parts of the world
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Nutrient Enrichment In addition to transporting nutrients from one location to another – Humans have added entirely new materials, some of them toxins, to ecosystems
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Agriculture and Nitrogen Cycling Agriculture constantly removes nutrients from ecosystems – That would ordinarily be cycled back into the soil Figure 54.20
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings. Nitrogen is the main nutrient lost through agriculture – Thus, agriculture has a great impact on the nitrogen cycle Industrially produced fertilizer is typically used to replace lost nitrogen – But the effects on an ecosystem can be harmful
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sewage runoff contaminates freshwater ecosystems – Causing cultural eutrophication, excessive algal growth, which can cause significant harm to these ecosystems
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Acid Precipitation Combustion of fossil fuels – Is the main cause of acid precipitation
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings. North American and European ecosystems downwind from industrial regions – Have been damaged by rain and snow containing nitric and sulfuric acid Figure Europe North America
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings By the year 2000 – The entire contiguous United States was affected by acid precipitation Figure Field pH – – – – – – – – – –4.4 4.3
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings. Environmental regulations and new industrial technologies – Have allowed many developed countries to reduce sulfur dioxide emissions in the past 30 years
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Toxins in the Environment Humans release an immense variety of toxic chemicals – Including thousands of synthetics previously unknown to nature One of the reasons such toxins are so harmful – Is that they become more concentrated in successive trophic levels of a food web
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings. In biological magnification – Toxins concentrate at higher trophic levels because at these levels biomass tends to be lower Figure Concentration of PCBs Herring gull eggs 124 ppm Zooplankton ppm Phytoplankton ppm Lake trout 4.83 ppm Smelt 1.04 ppm
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings. In some cases, harmful substances – Persist for long periods of time in an ecosystem and continue to cause harm
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Atmospheric Carbon Dioxide One pressing problem caused by human activities – Is the rising level of atmospheric carbon dioxide
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Rising Atmospheric CO 2 Due to the increased burning of fossil fuels and other human activities – The concentration of atmospheric CO 2 has been steadily increasing Figure CO 2 concentration (ppm) 0.15 0.30 0.45 Temperature variation ( C) Temperature CO 2 Year
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings How Elevated CO 2 Affects Forest Ecology: The FACTS-I Experiment The FACTS-I experiment is testing how elevated CO 2 – Influences tree growth, carbon concentration in soils, and other factors over a ten-year period Figure 54.25
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Greenhouse Effect and Global Warming The greenhouse effect is caused by atmospheric CO 2 – But is necessary to keep the surface of the Earth at a habitable temperature
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings. Increased levels of atmospheric CO 2 are magnifying the greenhouse effect – Which could cause global warming and significant climatic change
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Depletion of Atmospheric Ozone Life on Earth is protected from the damaging effects of UV radiation – By a protective layer or ozone molecules present in the atmosphere
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Satellite studies of the atmosphere – Suggest that the ozone layer has been gradually thinning since 1975 Figure Ozone layer thickness (Dobson units) Year (Average for the month of October)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The destruction of atmospheric ozone – Probably results from chlorine-releasing pollutants produced by human activity Figure Chlorine from CFCs interacts with ozone (O 3 ), forming chlorine monoxide (ClO) and oxygen (O 2 ). Two ClO molecules react, forming chlorine peroxide (Cl 2 O 2 ). Sunlight causes Cl 2 O 2 to break down into O 2 and free chlorine atoms. The chlorine atoms can begin the cycle again. Sunlight ChlorineO3O3 O2O2 ClO Cl 2 O 2 O2O2 Chlorine atoms
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Scientists first described an “ozone hole” – Over Antarctica in 1985; it has increased in size as ozone depletion has increased Figure 54.28a, b (a) October 1979 (b) October 2000