Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Quantifying Communities Community structure is measured in different ways. Species Richness: The number of _______ species in the community Species Diversity: The number and _________of species in thecommunity

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Are All Ecosystems Equal? Different ecosystems have different amounts of biodiversity (and produce different amounts of _________)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Diversity = Stability There is a direct relationship between biodiversity in an ecosystem and the stability of the ecosystem. Genetic Diversity Species Diversity Biome Diversity

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ch 55: Ecosystems Ecosystems, Energy, and Matter An ecosystem consists of all the organisms living in a community (___________ factors) and all the abiotic factors with which they rely on

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The only constant is change Ecosystems are constantly changing. Disturbance: Anything that disrupts the homeostatic balance of an ecosystem.

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How does Energy and Chemical movement different through ecosystems? 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 Trophic Efficiency -Only __% of Sun’s energy reaches the earth -Most energy does ____ move up the food chain

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings We measure Productivity with Pyramids! -Pyramid of Energy -Shows that within a food chain, only ~___% of energy at any trophic level will be passed on to the next trophic level. 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 Biomass also measures Productivity Energy is added in to a community by _______. Pyramids of Biomass show that ________ usually occupy the greatest biomass in the ecosystem. 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 Pyramids of Numbers A pyramid of numbers represents the number of __________ 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 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 Primary Productivity is the amount of light energy converted to chemical energy by autotrophs during a given time period Does all of the energy absorbed the sun go into the bodies (biomass) of producers?

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Productivity How is Gross primary productivity (GPP) different from net primary productivity (NPP)? NPP = GPP – (metabolism + lost energy)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Are all ecosystems equally productive? Does productivity fluctuates seasonally, and with climate?

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Different ecosystems vary in their net primary production – And in their contribution to the total NPP on Earth Percentage of Earth’s surface area (a) Average net primary production (g/m 2 /yr) (b) (c)

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 00 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 Matter Cycles Matter cycles between abiotic and ________ reservoirs in an ecosystem

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Producers & Decomposers Producers move matter from ______ sources (sun, soil) to biotic sources. Decomposers move matter from biotic sources to abiotic sources.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Nutrients cycle through ecosystems Decomposers or detritivores (mainly bacteria and fungi) recycle essential elements b y decomposing organic material and returning elements to inorganic reservoirs Figure 54.3

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings What are the Limiting Factors in Marine Ecosystems? Figure 54.6 (a) Phytoplankton biomass and phosphorus concentration (b) Phytoplankton response to nutrient enrichment Great South Bay Moriches Bay Shinnecock Bay Starting algal density Unenriched control Ammonium enriched Phosphate enriched Station number Phytoplankton (millions of cells per mL) Inorganic phosphorus (  g atoms/L) Phytoplankton (millions of cells/mL) Station number CONCLUSION Since adding phosphorus, which was already in rich supply, had no effect on Nannochloris growth, whereas adding nitrogen increased algal density dramatically, researchers concluded that nitrogen was the nutrient limiting phytoplankton growth in this ecosystem. Phytoplankton Inorganic phosphorus RESULTS Phytoplankton abundance parallels the abundance of phosphorus in the water (a). Nitrogen, however, is immediately taken up by algae, and no free nitrogen is measured in the coastal waters. The addition of ammonium (NH 4  ) caused heavy phytoplankton growth in bay water, but the addition of phosphate (PO 4 3  ) did not induce algal growth (b).

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Experiments in another ocean region – Showed that iron limited primary production Table 54.1

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings What happens when you have too many nutrients? Eutrophication of lakes (algae on top prevent light from reaching bottom, dead algae add to biomass and all decrease Oxygen which kills fish, etc Figure 54.7

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 ________ Figure Trophic level Secondary consumers Primary consumers Primary producers

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 What drives the water cycle versus 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 How does Nitrogen enter and leave ecosystems?

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 Why is Phosphorus considered more of a Local nutrient?

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings How does human activity 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 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 Contamination of Aquatic Ecosystems The critical load for a nutrient – Is the amount of that nutrient that can be absorbed by plants in an ecosystem without damaging it

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings When excess nutrients are added to an ecosystem, the critical load is exceeded – And the remaining nutrients can contaminate groundwater and freshwater and marine ecosystems

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