Chapter 46 Ecosystems

1. Chapter 46Ecosystems

2. 46.1 Too Much of a Good Thing • Phosphorus is an essential element for building ATP, phospholipids, nucleic acids, and other biological compounds • A lack of available phosphorus is often the main factor limiting growth of producers at the base of the food web • Phosphate-rich fertilizers spread on lawns and agricultural fields can run off and pollute rivers or lakes • The addition of nutrients to an aquatic ecosystem (eutrophication) disrupts nutrient cycles

3. Lawn Fertilizer and Water Pollution

4. Effect of Phosphate Pollution nitrogen, carbon added nitrogen, carbon, phosphorus added

5. 46.2 The Nature of Ecosystems • Ecosystem • An array of organisms and a physical environment, all interacting through a one-way flow of energy and a cycling of nutrients • Sustained by ongoing inputs of energy and nutrients (open system)

6. Overview of Participants • Primary producers(autotrophs) • Obtain energy from nonliving sources (sunlight) • Build organic compounds from CO2 and water • Consumers (heterotrophs) • Get energy and carbon from organic sources • Carnivores, herbivores, parasites, omnivores

7. Overview of Participants • Detritivores, such as earthworms and crabs, eat small particles of organic matter (detritus) • Decomposers, such as bacteria and fungi, feed on organic wastes and remains and break them down into inorganic building blocks

8. Energy and Nutrients • Energy flows one way • Producers capture light energy and convert it to bond energy in organic molecules (photosynthesis) • Metabolic reactions break bonds (aerobic respiration) and give off heat, which is not recycled • Nutrients are cycled • Producers take up inorganic compounds from the environment; decomposers return them

9. light energy Producers plants; photosynthetic protists and bacteria energy in chemical bonds materials cycling Consumers animals; fungi; heterotrophic protists, bacteria, and archaeans heat energy Stepped Art Figure 46-3 p830

10. ANIMATED FIGURE: One-way energy flow and materials cycling To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

11. Trophic Structure of Ecosystems • Trophic levels • Hierarchy of feeding relationships in which energy is transferred when one organism eats another • Each trophic level is a number of transfers away from the system’s original energy input

12. Food Chain • Food chain • A sequence of steps by which some energy captured by primary producers is transferred to organisms at successively higher trophic levels • Omnivores feed at several levels

13. Tallgrass Prairie: Food Chain and Trophic Levels

14. ANIMATED FIGURE: Food chain To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

15. Take-Home Message: What is the trophic structure of an ecosystem? • An ecosystem includes a community of organisms that interact with their physical environment by a one-way energy flow and a cycling of materials. • Autotrophs tap into an environmental energy source and make their own organic compounds from inorganic raw materials. They are the ecosystem’s primary producers. • Autotrophs are at the first trophic level of a food chain, a linear sequence of feeding relationships that proceeds through one or more levels of heterotrophs or consumers.

16. ANIMATION: The role of organisms in an ecosystem To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

17. 46.3 The Nature of Food Webs • Food webs • Multiple interconnecting food chains, including grazing and detrital food chains • Grazing food web • Energy stored in producers flows to herbivores, which tend to be large animals • Detrital food web • Energy in producers flows to decomposers and detritivores, which tend to be small

18. Land Versus Aquatic Food Chains • In land ecosystems, most of the energy stored in producers moves through detrital food chains • In aquatic ecosystems, most of the energy in producers flows to grazers rather than detritivores

19. human (Inuk) arctic wolf arctic fox Higher Trophic Levels A sampling of carnivores that feed on herbivores and one another gyrfalcon snowy owl ermine mosquito flea Second Trophic Level Parasitic consumers feed at more than one trophic level. A sampling of primary consumers (herbivores) that eat plants vole arctic hare lemming Detritivores and decomposers (nematodes, annelids, saprobic insects, protists, fungi, bacteria) First Trophic Level Examples of primary producers (plants) grasses, sedges purple saxifrage arctic willow Stepped Art Figure 46-5 p832

20. ANIMATED FIGURE: Food webs To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

21. How Many Transfers? • Cumulative energy losses from energy transfers between trophic levels limits the length of food chains to four or five trophic levels • Food chains tend to be shortest in variable habitats, longer in stable habitats • Food webs with more carnivores have fewer connections; herbivores have more connections

22. East River Valley, Colorado

23. Model for East River Valley Food Web

24. Take-Home Message: How does energy flow affect food chains and food webs? • Tissues of living plants and other producers are the basis for grazing food webs. Remains of producers are the basis for detrital food webs. • Nearly all ecosystems include both grazing food webs and detrital food webs that interconnect as the system’s food web. • The cumulative energy losses from energy transfers between trophic levels limits the length of food chains. • Even when an ecosystem has many species, trophic interactions link each species with many others.

25. 46.4 Energy Flow • Primary producers capture energy and take up nutrients, which move to other trophic levels • Primary production • Rate at which producers capture and store energy • Gross primary production – amount captured • Net primary production – amount used in growth

26. Net Primary Productivity

27. Winter Productivity North America Atlantic Ocean in Winter Africa

28. Spring Productivity North America Atlantic Ocean in Spring Africa

29. Ecological Pyramids • A biomass pyramiddepicts dry weight of organisms at each trophic level in an ecosystem • Largest tier is usually producers • For some aquatic systems, pyramid is inverted • An energy pyramiddepicts the energy that enters each trophic level in an ecosystem • Largest tier is always producers

30. top carnivores (gar and bass) 1.5 carnivores (smaller fishes, invertebrates) 11 37 herbivores (plant-eating fishes, invertebrates, turtles) 5 detritivores (crayfish) and decomposers (bacteria) producers (algae and aquatic plants) 809 Biomass (in grams per square meter) Biomass Pyramid: Silver Springs Stepped Art

31. top carnivores detritivores + decomposers = 5,060 21 carnivores 383 herbivores 3,368 producers 20,810 Energy Pyramid: Silver Springs Stepped Art

32. Annual Energy Flow: Silver Springs

33. ANIMATED FIGURE: Energy flow at Silver Springs To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

34. Ecological Efficiency • 5 to 30% of energy in tissues of organisms at one trophic level ends up in tissues of those at the next trophic level • Some energy is lost as heat • Some biomass is not digested • Efficiency of transfers tends to be greatest in aquatic systems (less lignin, more ectotherms)

35. Take-Home Message:How does energy flow through ecosystems? • Primary producers capture energy and convert it into biomass. We measure this process as primary production. • A biomass pyramid depicts dry weight of organisms at each trophic level. Its largest tier is usually producers, but the pyramid for some aquatic systems is inverted. • An energy pyramid depicts the amount of energy that enters each level. Its largest tier is always at the bottom (producers). • The efficiency of energy transfers tends to be greatest in aquatic systems, where primary producers usually lack lignin and consumers tend to be ectotherms.

36. 46.5 Biogeochemical Cycles • In a biogeochemical cycle, an essential element moves from nonliving environmental reservoirs, into living organisms, then back to the reservoirs • Elements essential to life (nutrients) include oxygen, hydrogen, carbon, nitrogen, phosphorus

37. Biogeochemical Cycles • Chemical and geologic processes move elements to, from, and among environmental reservoirs • Nutrients move from inorganic reservoirs (rocks, sediments, water, atmosphere) to living systems through primary producers • Photosynthetic organisms take up dissolved ions and carbon dioxide; bacteria fix nitrogen gas

38. Biogeochemical Cycles Atmosphere Rocks and sediments Seawater and fresh water Living organisms Nonliving environmental reservoirs

39. Take-Home Message:What is a biogeochemical cycle? • A biogeochemical cycle is the slow movement of a nutrient among environmental reservoirs and into, through, and out of food webs.

40. 46.6 The Water Cycle • The water cyclemoves water moves from the world ocean (main reservoir) through the atmosphere (by evaporation and transpiration), onto land (by condensation and precipitation), then back to the ocean • Oceans cover about 70% of Earth’s surface, so most rainfall returns water directly to the oceans

41. Table 46-1 p837

42. Where Water Moves • A watershedis an area from which all precipitation drains into a specific waterway • Groundwater includes soil water and water in aquifers (permeable rock layers that hold water) • Runoff is water that flows over saturated ground into streams • Flowing water carries nutrients from place to place

43. Windborne water vapor Precipitation onto the land Evaporation from land plants (transporation) Precipitation into ocean Surface and groundwater flow Atmosphere Evaporation from ocean Land Ocean Stepped Art Figure 46-11 p837

44. Limited Fresh Water • Most of Earth’s water is too salty to drink or irrigate crops • Overdrafts from aquifers are common; water is drawn from aquifers faster than natural processes replenish it • When too much fresh water is withdrawn from a coastal aquifer, saltwater moves in and replaces it • In the US, about 80% of the water used by humans is for irrigating agricultural fields

45. Groundwater Troubles

46. Take-Home Message: What is the water cycle and how do human activities affect it? • Water moves slowly from the world ocean—the main reservoir—through the atmosphere, onto land, then back to the ocean. • Fresh water makes up only a tiny portion of the global water supply. Excessive water withdrawals threaten many sources of drinking water.

47. 46.7 Carbon Cycle • In thecarbon cycle, carbon moves among Earth’s atmosphere, oceans, rocks, and soils, and into and out of food webs • It is an atmospheric cycle – the atmosphere holds about 760 gigatons (billion tons) of carbon, mainly in the form of carbon dioxide (CO2)

48. Terrestrial Carbon Cycle • Land plants incorporate CO2 from the atmosphere into their tissues through photosynthesis • Plants and other organisms release CO2 into the atmosphere through aerobic respiration • Soil contains more than twice as much carbon as the atmosphere – consisting of humus and living soil organisms

49. Carbon Stored in Plants and Soils

50. Marine Carbon Cycle • Most of the annual cycling of carbon occurs between the ocean and the atmosphere • Bicarbonate (HCO3–) is the main inorganic carbon in seawater • Photosynthesis, aerobic respiration, decomposition, and sediments contribute to the marine carbon cycle • Marine sediments and sedimentary rocks formed from calcium carbonate–rich shells are Earth’s largest carbon reservoir, with more than 65 gigatons