The document discusses ecosystems and energy flow through ecosystems. It explains that ecosystems consist of organisms and the abiotic environment, and that energy and nutrients cycle through the biotic and abiotic components. It then describes how energy enters ecosystems through primary producers like plants, and is transferred to higher trophic levels as it is consumed but most is lost through respiration.

2. Chapter 51

5. External energy source PRIMARY PRODUCERS CONSUMERS DECOMPOSERS ABIOTIC ENVIRONMENT Figure 51.1

6. External energy source PRIMARY PRODUCERS ABIOTIC ENVIRONMENT Figure 51.1 CONSUMERS DECOMPOSERS

9. Energy source: 1,254,000 kcal/m 2 /year 0.8% energy captured by photosynthesis. Of this... … 45% supports growth (Net primary production) … 11% enters grazing food web … 34% enters decomposer food web as dead material … 55% lost to respiration Figure 51.2

10. Energy source: 1,254,000 kcal/m 2 /year Figure 51.2 … 11% enters grazing food web … 34% enters decomposer food web as dead material 0.8% energy captured by photosynthesis. Of this... … 45% supports growth (Net primary production) … 55% lost to respiration

11. 0–100 100–200 200–400 400–600 600–800 >800 Productivity ranges (g/m 2 /yr) Figure 51.3a Terrestrial productivity

12. <35 35–55 55–90 >90 Productivity ranges (g/m 2 /yr) Figure 51.3b Marine productivity

13. 80.7% respiration 17.7% excretion 1.6% growth and reproduction Energy derived from plants Figure 51.4

14. Predators of decomposers: Spider Centipede Mushroom Earthworm Primary decomposers: Bacteria and archaea Millipede Nematodes Pillbugs Salamander Figure 51.5 Puffball Puffball 305 nm 49.4 µm

17. Trophic level 4 3 2 1 Feeding strategy Secondary carnivore Carnivore Herbivore Autotroph Grazing food chain Decomposer food chain Cricket Maple tree leaves Owl Shrew Earthworm Dead maple leaves Cooper’s hawk Robin Figure 51.6a Trophic levels

18. 4 Secondary carnivore 3 Carnivore 2 Herbivore 1 Autotroph Productivity Figure 51.6b Pyramid of productivity

20. Pisaster (a sea star) Thais (a snail) Bivalves (clams, mussels) Figure 51.7a Food chain

21. Pisaster Thais Chitons Limpets Bivalves Acorn barnacles Gooseneck barnacles Figure 51.7b Food web

23. Number of observations Number of links in food chain 10 8 6 4 2 0 Streams Lakes Terrestrial Figure 51.7c Food chains tend to have few links. Average number of links = 3.5 1 2 3 4 5 6

25. Assimilation Loss to erosion or leaching into groundwater Soil nutrient pool Decomposer food web Detritus Death Herbivore Uptake Plants Death Consumption Feces or urine Figure 51.8

26. Boreal forest Figure 51.9 upper

27. Tropical rain forest Figure 51.9 lower

29. Devegetation experiment Choose two similar watersheds. Document nutrient levels in soil organic matter, plants, and streams. Figure 51.10a upper

30. Figure 51.10a lower Clearcut Control Devegetate one watershed and leave the other intact. Monitor the amount of dissolved substances in streams.

31. Devegetated Net dissolved substance (kg/ha) Control 1000 800 600 400 200 0 Year Figure 51.10b Nutrient runoff results 1965–66 1966–67 1967–68 1968–69 1969–70

33. THE GLOBAL CARBON CYCLE All values in gigatons of carbon per year Physical and chemical processes: 92 2 Ocean: 40,000 Rivers: 1 Land, biota, soil, litter, peat: 2000 Decomposition: 50 Respiration: 50 Photosynthesis: 102 Physical and chemical processes: 90 Deforestation: 1.5 Fossil fuel use: 6.0 Atmosphere: 750 (in 1990) +3.5 per year Aquatic ecosystems Terrestrial ecosystems Human–induced changes Figure 51.11

34. THE GLOBAL NITROGEN CYCLE Nitrogen fixing cyanobacteria Mud Decomposition of detritus into ammonia Nitrogen-fixing bacteria in roots and soil Industrial fixation Protein and nucleic acid synthesis Atmospheric nitrogen (N 2 ) Bacteria in mud use N-containing molecules as energy sources, excrete (N 2 ) Run–off Lightning and rain Figure 51.13a

35. Land use Fossil fuel use Year Annual flux of carbon (10 15 g) 6 5 4 3 2 1 0 Figure 51.12a Human-induced increases in CO 2 flux over time 1860 1880 1900 1920 1940 1960 1980

36. Year CO 2 concentration (ppm) 360 350 340 330 320 310 1960 1970 1980 1990 Figure 51.12b Atmospheric CO 2

37. Natural sources Human sources Amount of nitrogen (gigatons/year) 160 140 120 100 80 60 40 20 0 Sources of nitrogen fixation Lightning Biological fixation Fossil fuels Nitrogen fertilizer Nitrogen- fixing crops Figure 51.13b