1. Chapter 55 Ecosystems

2. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Overview: Ecosystems An ecosystem consists of all the organisms living in a community, as well as 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 while matter cycles within them.

3. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings I. Conservation of Mass Matter cannot be created or destroyed. Chemical elements are recycled Ecosystems are open systems, absorbing energy and mass and releasing heat and waste products.

4. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Autotrophs build organic molecules (photosynthesis or chemosynthesis) Heterotrophs depend on other organisms. Energy and nutrients pass from producers (autotrophs) to primary consumers (herbivores) to secondary consumers (carnivores) to tertiary consumers (carnivores that feed on other carnivores).

5. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Detritivores (decomposers) are consumers that derive their energy from detritus, nonliving organic matter. – Prokaryotes and fungi Decomposition connects all trophic levels.

6. Fungi decomposing a dead tree

7. Energy and Nutrient Dynamics in an Ecosystem Microorganisms and other detritivores Tertiary consumers Secondary consumers Primary consumers Primary producers Detritus Heat Sun Chemical cycling Key Energy flow

8. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings II. Energy controls production Primary production = amount of light energy converted to chemical energy by autotrophs. Amount of photosynthetic production sets the spending limit for an ecosystem’s energy budget. (amount of sunlight = amount of output)

9. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings A. Gross and Net Primary Production Total primary production is known as the ecosystem’s gross primary production = GPP Net primary production = NPP GPP - energy used by producers for respiration. NPP = GPP - Respiration Only NPP is available to consumers. Standing crop = total biomass of photosynthetic autotrophs at a given time.

10. Net primary production (kg carbon/m 2 ·yr) 0 1 2 3 · Global net primary production in 2002

11. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings III. Production in Aquatic Ecosystems Both light and nutrients control primary production. Depth of light penetration affects primary production in the photic zone of an ocean or lake.

12. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings A. Nutrient Limitation More than light, nutrients limit primary production in geographic regions of the ocean and in lakes. Limiting nutrient = element that must be added for production to increase in an area. Nitrogen and phosphorous are typically the nutrients that most often limit marine production.

13. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Upwelling of nutrient-rich waters in oceans contributes to regions of high primary production. In some areas, sewage runoff has caused eutrophication (high levels of algae, decay, low oxygen) of lakes, which can lead to loss of most fish species.

14. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings IV. Production in Terrestrial Ecosystems Temperature and moisture affect primary production on a large scale. Actual evapotranspiration is the water annually transpired by plants and evaporated from a landscape. Locally, soil nutrient is often the limiting factor in primary production.

15. Net primary production (g/m 2 ·yr) Relationship between net primary production and actual evapotranspiration in six terrestrial ecosystems Tropical forest Actual evapotranspiration (mm H 2 O/yr) Temperate forest Mountain coniferous forest Temperate grassland Arctic tundra Desert shrubland 1,500 1,000 5000 0 1,000 2,000 3,000 ·

16. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings V. Energy transfer is 10% efficient Secondary production = the amount of chemical energy in food converted to new biomass during a given period of time. – Ex. When a caterpillar feeds on a leaf, only about one-sixth of the leaf’s energy is used for secondary production. Production efficiency = fraction of energy stored in food that is not used for respiration. Approximately 0.1% of chemical energy fixed by photosynthesis reaches a tertiary consumer.

17. Energy partitioning within a link of the food chain Cellular respiration 100 J Growth (new biomass) Feces 200 J 33 J 67 J Plant material eaten by caterpillar

18. Primary producers 100 J 1,000,000 J of sunlight 10 J 1,000 J 10,000 J Primary consumers Secondary consumers Tertiary consumers

19. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Biomass pyramid – amount of living matter in an area – Sharp decrease at successively higher levels Some aquatic ecosystems have inverted biomass pyramids (producers are consumed so quickly that they are outweighed by primary consumers)

20. Pyramids of biomass = standing crop: (a) Most ecosystems (data from a Florida bog) Primary producers (phytoplankton) (b) Some aquatic ecosystems (data from the English Channel) Trophic level Tertiary consumers Secondary consumers Primary consumers Primary producers Trophic level Primary consumers (zooplankton) Dry mass (g/m 2 ) Dry mass (g/m 2 ) 1.5 11 37 809 21 4

21. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Ecosystems – Andersen – 14 minEcosystems – Andersen

22. Nutrient Cycling Reservoir A Reservoir B Organic materials available as nutrients Fossilization Organic materials unavailable as nutrients Reservoir DReservoir C Coal, oil, peat Living organisms, detritus Burning of fossil fuels Respiration, decomposition, excretion Assimilation, photosynthesis Inorganic materials available as nutrients Inorganic materials unavailable as nutrients Atmosphere, soil, water Minerals in rocks Weathering, erosion Formation of sedimentary rock

23. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings VI. Water Cycle 97% oceans, 2% ice, and 1% is in lakes, rivers, and groundwater. evaporation, transpiration, condensation, precipitation, and surfacewater and groundwater.

24. Nutrient Cycles: Water Cycle Precipitation over land Transport over land Solar energy Net movement of water vapor by wind Evaporation from ocean Percolation through soil Evapotranspiration from land Runoff and groundwater Precipitation over ocean

25. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings VII. Carbon Cycle C stored in fossil fuels, soils and sediments, solutes in oceans, plant and animal biomass, and the atmosphere. CO 2 is taken up and released through photosynthesis and respiration; volcanoes and burning of fossil fuels add CO 2 to the atmosphere.

26. Nutrient Cycles: Carbon Cycle Higher-level consumers Primary consumers Detritus Burning of fossil fuels and wood Phyto- plankton Cellular respiration Photo- synthesis Photosynthesis Carbon compounds in water Decomposition CO 2 in atmosphere

27. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings VIII. Nitrogen Cycle The main reservoir of nitrogen is the atmosphere (N 2 ), though this nitrogen must be converted to NH 4 + or NO 3 – for uptake by plants, via nitrogen fixation by bacteria.

28. Nutrient Cycles: Nitrogen Cycle Decomposers N 2 in atmosphere Nitrification Nitrifying bacteria Nitrifying bacteria Denitrifying bacteria Assimilation NH 3 NH 4 NO 2 NO 3 + – – Ammonification Nitrogen-fixing soil bacteria Nitrogen-fixing bacteria

29. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings IX. Phosphorus Cycle Phosphate (PO 4 3– ) is the most important inorganic form of phosphorus. Stored in sedimentary rocks of marine origin, oceans, and organisms. Phosphate binds with soil particles, and movement is often localized.

30. Nutrient Cycles: Phosphorous Cycle Leaching Consumption Precipitation Plant uptake of PO 4 3– Soil Sedimentation Uptake Plankton Decomposition Dissolved PO 4 3– Runoff Geologic uplift Weathering of rocks

31. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings X. Decomposition and Nutrient Cycling Rates Decomposers = play a key role in chemical cycling. The rate of decomposition is controlled by temperature, moisture, and nutrient availability. Rapid decomposition = low levels of nutrients in the soil.

32. How does temperature affect litter decomposition in an ecosystem? Ecosystem type EXPERIMENT RESULTS Arctic Subarctic Boreal Temperate Grassland Mountain P O D J R Q K B,C E,F H,I L N U S T M G A A 80 70 60 50 40 30 20 10 0 –15 –10 –50510 15 Mean annual temperature (ºC) Percent of mass lost B C D E F G H I J K L M N O P Q R S T U

33. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings A. Agriculture and Nitrogen Cycling Agriculture removes nutrients from the soil. Nitrogen is the main nutrient lost through agriculture Fertilizer is typically used to replace lost nitrogen, but effects on an ecosystem can be harmful.

34. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings B. Contamination of Aquatic Ecosystems Critical load for a nutrient is the amount that plants can absorb without damaging the ecosystem. When have excess nutrients, critical load is exceeded. Remaining nutrients can contaminate groundwater and ecosystems. – Sewage runoff causes eutrophication

35. The dead zone arising from nitrogen pollution in the Mississippi basin WinterSummer

36. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings XI. Acid Precipitation Combustion of fossil fuels is the main cause Acid precipitation changes soil pH and causes leaching of calcium and other nutrients. Effects areas downwind from industry

37. Changes in the pH of precipitation at Hubbard Brook Year 20001995 1990 19851980 19751970 19651960 4.0 4.1 4.2 4.3 4.4 4.5 pH

38. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings XII. Toxins Humans release many toxic chemicals Toxins are harmful because they become more concentrated in successive trophic levels. Biological magnification concentrates toxins at higher trophic levels. – Ex PCBs and many pesticides such as DDT

39. Biological Magnification of PCBs in a Great Lakes food web Lake trout 4.83 ppm Concentration of PCBs Herring gull eggs 124 ppm Smelt 1.04 ppm Phytoplankton 0.025 ppm Zooplankton 0.123 ppm

40. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings XIII. Greenhouse Gases and Global Warming Burning of fossil fuels and other human activities, the [CO 2 ] has been steadily increasing.

41. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Greenhouse effect = CO 2, water vapor, and other greenhouse gases reflect infrared radiation back toward Earth Increased levels of CO 2 are magnifying the greenhouse effect, which could cause global warming and climatic change. A warming trend would also affect the geographic distribution of precipitation.

42. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings XIV. Depletion of Ozone Ozone protects life on Earth from damaging effects of UV radiation Destruction of ozone probably results from chlorine-releasing pollutants such as CFCs (chloroflorocarbons) produced by human activity. Causes DNA damage, hole is getting smaller bc of an international agreement in 1987

43. How free chlorine in the atmosphere destroys ozone O2O2 Sunlight Cl 2 O 2 Chlorine Chlorine atom O3O3 O2O2 ClO

44. Erosion of Earth’s ozone shield (a) September 1979(b) September 2006

45. Ecosystem Changes – Andersen Biodiversity - Andersen

46. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings You should now be able to: 1.Explain how the first and second laws of thermodynamics apply to ecosystems. 2.Define and compare gross primary production, net primary production, and standing crop. 3.Explain why energy flows but nutrients cycle within an ecosystem. 4.Explain what factors may limit primary production in aquatic ecosystems.

47. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 5.Distinguish between the following pairs of terms: primary and secondary production, production efficiency and trophic efficiency. 6.Explain why worldwide agriculture could feed more people if all humans consumed only plant material. 7.Describe the four nutrient reservoirs and the processes that transfer the elements between reservoirs.

48. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 8.Explain why toxic compounds usually have the greatest effect on top-level carnivores. 9.Describe the causes and consequences of ozone depletion.