Chapter 42 Ecosystems (Sections 42.1 - 42.6)

1. Chapter 42Ecosystems(Sections 42.1 - 42.6)

2. 42.1 Too Much of a Good Thing • Human activities can disrupt nutrient cycles that have been operating since long before humans existed • Phosphorus is often a limiting factor for aquatic producers, and sudden addition of phosphorus (eutrophication) causes algal blooms that cloud water and threaten aquatic species • eutrophication • Nutrient enrichment of an aquatic ecosystem

3. Experiment: Phosphorus Enrichment

4. Experiment: Phosphorus Enrichment nitrogen, carbon added nitrogen, carbon, phosphorus added Fig. 42.1, p. 709

5. 42.2 The Nature of Ecosystems • In ecosystems, organisms and their environment interact through a one-way flow of energy and a cycling of nutrients • Ecosytems require ongoing inputs of energy (open systems) • Nutrients taken up by producers are returned to the environment by decomposers, then taken up again

6. Energy Flows, Nutrients Cycle • Light energy that enters the system returns to the environment as heat • Nutrients are continually recycled

7. Energy Flows, Nutrients Cycle light energy Producers plants; photosynthetic protists and bacteria energy in chemical bonds materials cycling Consumers animals; fungi; heterotrophic protists, bacteria, and archaeans heat energy Fig. 42.2, p. 710

8. light energy Producers plants; photosynthetic protists and bacteria energy in chemical bonds materials cycling Consumers animals; fungi; heterotrophic protists, bacteria, and archaeans heat energy Energy Flows, Nutrients Cycle Stepped Art Fig. 42.2, p. 710

9. ANIMATION: 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

10. Primary Producers and Production • An ecosystem runs on energy captured by primary producers • primary producer (autotroph) • An organism that obtains energy and nutrients from inorganic sources to build organic compounds • primary production • Rate at which producers capture and store energy • Varies by ecosystem, season, and nutrient availability

11. The Roles of Consumers • Consumers are described by their diets: • Herbivores (plants) • Carnivores (animal flesh) • Parasites (tissues of a living host) • Omnivores (plants and animals) • Detritivores (detritus) • Decomposers (waste and remains)

12. Key Terms • consumer • Organism that obtains energy and carbon by feeding on tissues, wastes, or remains of other organisms • detritivore • Consumer that feed on small bits of organic material • decomposer • Organism that feeds on biological remains and breaks organic material down into its inorganic subunits

13. Energy Flow and Nutrient Cycling • Heat energy is not recycled: • Energy captured by producers is converted to bond energy in organic molecules, and released by metabolic reactions that give off heat • Nutrients are recycled: • Producers take up inorganic molecules (nutrients) from the environment to form organic molecules • Decomposers break down organic molecules and return nutrients to the environment

14. 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

15. ANIMATION: 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

16. 42.3 Food Chains • Food chains describe how energy and materials are transferred from one organism to another • food chain • Description of who eats whom in one path of energy in an ecosystem – transfer of energy to higher trophic levels • trophic level • Position of an organism in a food chain

17. A Food Chain • First trophic level (primary producer): • Autotroph (grass) converts light to chemical energy • Second trophic level (primary consumer): • Grasshopper eats grass • Third trophic level (second-level consumer): • Bird eats grasshopper • Fourth trophic level (third-level consumer): • Coyote eats bird

18. A Food Chain

19. A Food Chain Fourth Trophic Level Third-level consumer coyote Third Trophic Level Second-level consumer sparrow Second Trophic Level Primary consumer grasshopper First Trophic Level Primary producer big bluestem grass Fig. 42.3, p. 711

20. A Food Chain Fig. 42.3.1, p. 711

21. A Food Chain Fig. 42.3.2, p. 711

22. A Food Chain Fig. 42.3.3, p. 711

23. A Food Chain Fig. 42.3.4, p. 711

24. Food Chain Limits • Energy captured by producers usually passes through no more than four or five trophic levels • The length of food chains is restricted by the inefficiency of energy transfers • Only 5-30% of energy in an organism at one trophic level ends up in tissues of an organism at the next trophic level

25. 42.4 Food Webs • Food chains of an ecosystem cross-connect as a food web • Food web structure reflects environmental constraints and the inefficiency of energy transfers among trophic levels • food web • Set of cross-connecting food chains

26. Types of Food Chains • Food webs include two types of interconnecting food chains: • grazing food chain • Energy transferred from producers to herbivores (grazers) • detrital food chain • Energy transferred directly from producers to detritivores (worms or insects) • Major food chain in land ecosystems

27. Arctic Food Web

28. Arctic Food Web 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. Major parts of the buffet of primary consumers (herbivores) vole arctic hare lemming Detritivores and decomposers (nematodes, annelids, saprobic insects, protists, fungi, bacteria) First Trophic Level This is just part of the buffet of primary producers. grasses, sedges purple saxifrage arctic willow Fig. 42.4, p. 712

29. Arctic Food Web Fig. 42.4.1, p. 712

30. Arctic Food Web Fig. 42.4.2, p. 712

31. Arctic Food Web Fig. 42.4.3, p. 712

32. Arctic Food Web Fig. 42.4.4, p. 712

33. Arctic Food Web Fig. 42.4.5, p. 712

34. Arctic Food Web Fig. 42.4.6, p. 712

35. Arctic Food Web Fig. 42.4.7, p. 712

36. Arctic Food Web Fig. 42.4.8, p. 712

37. Arctic Food Web Fig. 42.4.9, p. 712

38. Arctic Food Web Fig. 42.4.10, p. 712

39. Arctic Food Web Fig. 42.4.11, p. 712

40. Arctic Food Web Fig. 42.4.12, p. 712

41. Arctic Food Web Fig. 42.4.13, p. 712

42. Arctic Food Web Fig. 42.4.14, p. 712

43. 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. Major parts of the buffet of primary consumers (herbivores) vole arctic hare lemming Detritivores and decomposers (nematodes, annelids, saprobic insects, protists, fungi, bacteria) First Trophic Level This is just part of the buffet of primary producers. grasses, sedges purple saxifrage arctic willow Arctic Food Web Stepped Art Fig. 42.4, p. 712

44. ANIMATION: 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

45. Trophic Interactions in Ecosystems • Understanding links in food webs helps ecologists predict how ecosystems respond to change • Computer models show that all species in an ecosystem are closely linked by trophic interaction • Even in large communities with many species, 95% of species are within three links of one another

46. A Land Food Web

47. ANIMATION: Rainforest food web 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

48. BBC Video: Seed Banks Helping to Save Our Fragile Ecosystem

49. BBC Video: The Vanishing Honeybee’s Impact on Our Food Supply

50. BBC Video: What is the Environmental Cost for Your Food?