Chapter 55 Ecosystems Power Point Lectures for Biology

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 • Regardless of an ecosystem’s size – Its dynamics involve two main processes: energy flow and chemical cycling • Energy flows through ecosystems IN ONE DIRECTION ONLY while matter CYCLES within them Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Visual Overview: Energy Flow Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Ecosystems and Physical Laws • Ecosystem ecology emphasizes energy flow and chemical cycling • Ecosystem ecologists view ecosystems As transformers of energy and processors of matter • 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 and nutrients pass from primary producers (autotrophs) – To primary consumers (herbivores) and then to secondary consumers (carnivores) • Energy flows IN ONE DIRE CTION ONLY through an ecosystem entering as light and exiting as heat – decomposition connects all trophic levels • Nutrients CYCLE within ecosystems Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Energy Flow & Nutrient Cycles Tertiary consumers Microorganisms and other detritivores Detritus Secondary consumers Primary producers Heat Key Chemical cycling Energy flow Figure 54. 2 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sun

Recycling Nutrients • 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

Primary Production in Ecosystems • Photosynthesis – Involves the use of light energy in the conversion of inorganic carbon into organic carbon. – Photosynthetic organisms include: • terrestrial plants, • seaweeds, • phytoplankton, • blue-green algae, • and zooxanthellae. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Primary Productivity in Ecosystems • 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 • The extent of photosynthetic production sets the spending limit for the energy budget of the entire ecosystem • The amount of solar radiation reaching the surface of the Earth limits the photosynthetic output of ecosystems • Only a small fraction of solar energy actually strikes photosynthetic organisms Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Fate of Solar Energy Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Primary Productivity • Gross Primary Productivity (GP) – The rate of production of organic matter from inorganic materials by autotrophic organisms • Respiration (R) – The rate of consumption of organic matter (conversion to inorganic matter) by organisms. • Net Primary Productivity (NP) – The net rate of organic matter produced as a consequence of both GP and R. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Primary Productivity: Formula 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 • 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

NPP of Varying Ecosystems • Different ecosystems vary considerably in their net primary production and in their contribution to the total NPP on Earth Open ocean Continental shelf Estuary 5. 2 0. 3 0. 1 Algal beds and reefs Upwelling zones Extreme desert, rock, sand, ice 4. 7 Desert and semidesert scrub Tropical rain forest 3. 5 3. 3 2. 9 2. 7 Savanna Cultivated land Boreal forest (taiga) Tropical seasonal forest Temperate deciduous forest Marine Terrestrial Freshwater (on continents) 3. 0 90 0. 04 0. 9 2, 200 10 22 900 7. 9 9. 1 600 9. 6 800 600 700 5. 4 3. 5 0. 6 140 1, 600 7. 1 1, 200 1, 300 4. 9 3. 8 2. 3 0. 3 2, 000 0. 4 0 0. 9 0. 1 500 1. 5 1. 3 1. 0 0. 4 Temperate evergreen forest Swamp and marsh Lake and stream 1. 2 2, 500 1. 7 1. 6 Tundra 24. 4 5. 6 1, 500 2. 4 1. 8 Temperate grassland Woodland shrubland Key 125 360 65. 0 250 20 30 40 50 60 0 500 1, 000 1, 500 2, 000 2, 500 (b) Average net primary production (g/m 2/yr) (a) Percentage of Earth’s surface area Figure 54. 4 a–c Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 0 5 10 15 20 (c) Percentage of Earth’s net primary production 25

Terrestrial Ecosystems • Overall, terrestrial ecosystems contribute about two-thirds of global NPP and marine ecosystems about one-third North Pole 60 N 30 N Equator 30 S 60 S South Pole 180 120 W 60 W Figure 54. 5 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 0 60 E 120 E 180

Environmental Factors Effect Production Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Primary Production in Marine and Freshwater Ecosystems • In marine and freshwater ecosystems – Both light and nutrients are important in controlling primary production • The depth of light penetration – Affects primary production throughout the photic zone of an ocean or lake • More than light, nutrients limit primary production – Both in different geographic regions of the ocean and in lakes Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Limits to Marine & Freshwater Ecosystems • A limiting nutrient is the element that must be added – In order for production to increase in a particular area • Nitrogen and phosphorous – Are typically the nutrients that most often limit marine production • The addition of large amounts of nutrients to lakes has a wide range of ecological impacts Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Algal Blooms • When an aquatic ecosystem receives a large input of a limiting nutrient, the result is often an immediate increase in the amount of algae & other producers – Leads to algal blooms – Algal blooms occur because there are suddenly more nutrients available…so producers can grow and reproduce more quickly…and if there aren’t enough consumers to eat the producers, then algal blooms can cover the surface of the water. • Runoff from heavy fertilizers can lead to algal blooms 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

Primary Production in Terrestrial and Wetland Ecosystems • In terrestrial and wetland ecosystems climatic factors – Such as temperature and moisture, affect primary production on a large geographic scale • On a more local scale – A soil nutrient is often the limiting factor in primary production Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Efficiency of Energy Transfer in Ecosystems • 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 Plant material eaten by caterpillar 200 J 67 J Feces Figure 54. 10 100 J 33 J Growth (new biomass) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cellular respiration

Production & Trophic Efficiency • The production efficiency of an organism – Is the fraction of energy stored in food that is not used for respiration • Trophic efficiency – Is the percentage of production transferred from one trophic level to the next – Usually ranges from 5% to 20% – Decreases moving between trophic levels because much energy is used for metabolism and life processes, and much is lost as entropy (heat waste) 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 Tertiary consumers Secondary consumers Primary producers Figure 54. 11 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 10 J 100 J 1, 000 J 10, 000 J 1, 000 J of sunlight

Pyramids of Biomass • One important ecological consequence of low trophic efficiencies can be represented in a biomass pyramid • Most biomass pyramids show a sharp decrease at successively higher trophic levels Dry weight (g/m 2) Tertiary consumers 1. 5 Secondary consumers 11 37 Primary consumers Primary producers 809 (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 Figure 54. 12 a Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Pyramids of Biomass • Certain aquatic ecosystems have inverted biomass pyramids Trophic level Dry weight (g/m 2) Primary consumers (zooplankton) 21 Primary producers (phytoplankton) 4 (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). Figire 54. 12 b 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 Tertiary consumers Number of individual organisms 3 Secondary consumers 354, 904 Primary consumers 708, 624 Primary producers Figure 54. 13 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 5, 842, 424

Biogeochemical Cycles • Biological and geochemical processes move nutrients between organic and inorganic parts of the ecosystem • Life on Earth – Depends on the recycling of essential chemical elements • Nutrient circuits that cycle matter through an ecosystem – Involve both biotic and abiotic components and are often called biogeochemical cycles 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

Biogeochemical Cycles • A general model of nutrient cycling – Includes the main reservoirs of elements and the processes that transfer elements between reservoirs Reservoir a Organic materials available as nutrients Living organisms, detritus Assimilation, photosynthesis Figure 54. 16 Reservoir b Organic materials unavailable as nutrients Fossilization Coal, oil, peat Respiration, decomposition, excretion Burning of fossil fuels Reservoir c Reservoir d Inorganic materials available as nutrients Inorganic materials unavailable as nutrients Atmosphere, soil, water Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Weathering, erosion Formation of sedimentary rock Minerals in rocks

Biogeochemical Cycles • The water cycle and the carbon cycle THE CARBON CYCLE THE WATER CYCLE CO 2 in atmosphere Transport over land Photosynthesis Solar energy Cellular respiration Net movement of water vapor by wind Precipitation over ocean Evaporation from ocean Precipitation over land Burning of fossil fuels and wood Evapotranspiration from land Percolation through soil Runoff and groundwater Figure 54. 17 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Carbon compounds in water Higher-level Primary consumers Detritus Decomposition

Biogeochemical Cycles • 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

Biogeochemical Cycles • The nitrogen cycle and the phosphorous cycle THE PHOSPHORUS CYCLE THE NITROGEN CYCLE N 2 in atmosphere Rain Geologic uplift Runoff Assimilation NO 3 Nitrogen-fixing bacteria in root nodules of legumes Decomposers Ammonification NH 3 Nitrogen-fixing soil bacteria Denitrifying bacteria Nitrification Plants Weathering of rocks Consumption Sedimentation Soil Plant uptake of PO 43 Leaching NO 2 NH 4+ Nitrifying bacteria Figure 54. 17 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Decomposition

Biogeochemical Cycles • 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 Consumers Producers Decomposers Nutrients available to producers Abiotic reservoir Figure 54. 18 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Geologic processes

The Human Population • 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 • Agriculture constantly removes nutrients from ecosystems – That would ordinarily be cycled back into the soil Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Nitrogen • 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 • 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

Contamination of Ecosystems • Sewage runoff contaminates freshwater ecosystems – Causing cultural eutrophication, excessive algal growth, which can cause significant harm to these ecosystems • Combustion of fossil fuels – Is the main cause of acid precipitation Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Contamination of Ecosystems • By the year 2000, the entire contiguous United States was affected by acid precipitation Figure 54. 22 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Field p. H 5. 3 5. 2– 5. 3 5. 1– 5. 2 5. 0– 5. 1 4. 9– 5. 0 4. 8– 4. 9 4. 7– 4. 8 4. 6– 4. 7 4. 5– 4. 6 4. 4– 4. 5 4. 3– 4. 4 4. 3

Contamination of Ecosystems • 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

Biological Magnification • In biological magnification toxins concentrate at higher trophic levels because at these levels biomass tends to be lower • In some cases, harmful substances persist for long periods of time in an ecosystem and continue to cause harm Concentration of PCBs Herring gull eggs 124 ppm Figure 54. 23 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Lake trout 4. 83 ppm Smelt 1. 04 ppm Zooplankton 0. 123 ppm Phytoplankton 0. 025 ppm

Toxins can become concentrated in successive trophic levels of food webs! Halogenated hydrocarbons or organochlorines: • Include DDT and PCBs, which are slow to biodegrade Dichloro-diphenyl-trichloro-ethane (DDT): • used as a pesticide from 1939 -late 1960 s • fat soluble compound • the world’s production has substantially decreased since it was banned in the West • detected in mud of deep sea and snow & ice of Antarctica Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Toxins can become concentrated in successive trophic levels of food webs! Effect of PCBs & DDT Polychloronated biphenyls (PCBs) • • • produced since 1944 banned in U. S. by 1979 used in production of electrical equipment, paints, plastics, adhesives, and coating compounds… found everywhere in the ocean released in env. by unregulated incineration of discarded products DDT & PCBs affects: • copepod and oyster development • death of shrimp and a variety of fish Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Biomagnification In biomagnification, there is a tendency for pollutants to concentration as they move from one link in a food chain to another…top level carnivores suffer the most harmful effects of biomagnification. 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 • Due to the increased burning of fossil fuels and other human activities – The concentration of atmospheric CO 2 has been steadily increasing Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Rising Atmospheric CO 2 1. 05 390 0. 90 380 0. 75 370 0. 60 360 0. 45 350 0. 30 340 CO 2 0. 15 330 Temperature variation ( C) CO 2 concentration (ppm) Temperature 0 320 0. 15 310 0. 30 300 0. 45 1960 1965 1970 1975 1980 1985 Year Figure 54. 24 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 1990 1995 2000 2005

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 • 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 • Satellite studies of the atmosphere – Suggest that the ozone layer has been gradually thinning since 1975 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Depletion of Atmospheric Ozone 350 Ozone layer thickness (Dobson units) 300 250 200 150 100 50 0 1955 1960 1965 Figure 54. 26 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 1970 1975 1980 1985 1990 1995 Year (Average for the month of October) 2000 2005

Depletion of Atmospheric Ozone • The destruction of atmospheric ozone probably results from chlorine-releasing pollutants produced by human activity 1 Chlorine from CFCs interacts with ozone (O 3), forming chlorine monoxide (Cl. O) and oxygen (O 2). Chlorine atoms O 2 Chlorine O 3 Cl. O O 2 Figure 54. 27 3 Sunlight causes Cl 2 O 2 to break down into O 2 and free chlorine atoms. The chlorine atoms can begin the cycle again. Cl. O Cl 2 O 2 Sunlight Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 2 Two Cl. O molecules react, forming chlorine peroxide (Cl 2 O 2).

Depletion of Atmospheric Ozone • Scientists first described an “ozone hole” over Antarctica in 1985; it has increased in size as ozone depletion has increased (a) October 1979 Figure 54. 28 a, b Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings (b) October 2000