1. Copyright © 2009 Pearson Education, Inc. 37.9 Food chains interconnect, forming food webs  Food web –A network of interconnecting food chains

2. Producers (plants) Primary consumers Secondary and primary consumers Tertiary and secondary consumers Quaternary, tertiary, and secondary consumers

3. Copyright © 2009 Pearson Education, Inc. 37.10 Species diversity includes relative abundance and species richness  Species diversity defined by two components –Species richness –Relative abundance  Plant species diversity in a community affects the animals  Species diversity has consequences for pathogens

7. Copyright © 2009 Pearson Education, Inc. 37.11 Keystone species have a disproportionate impact on diversity  Keystone species –A species whose impact on its community is larger than its biomass or abundance indicates –Occupies a niche that holds the rest of its community in place

8. Keystone absent

12. Copyright © 2009 Pearson Education, Inc. 37.12 Disturbance is a prominent feature of most communities  Disturbances –Events that damage biological communities –Storms, fire, floods, droughts, overgrazing, or human activity –The types, frequency, and severity of disturbances vary from community to community

13. Copyright © 2009 Pearson Education, Inc.  Communities change drastically following a severe disturbance  Ecological succession –Colonization by a variety of species –A success of change gradually replaces other species 37.12 Disturbance is a prominent feature of most communities

14. Copyright © 2009 Pearson Education, Inc.  Primary succession –Begins in a virtually lifeless area with no soil  Secondary succession –When a disturbance destroyed an existing community but left the soil intact 37.12 Disturbance is a prominent feature of most communities

15. Time Shrubs Annual plants Perennial plants and grasses Softwood trees such as pines Hardwood trees

16. Copyright © 2009 Pearson Education, Inc. 37.13 CONNECTION: Invasive species can devastate communities  Introduction of rabbits in Australia

17. Key Frontier of rabbit spread Origin: 1860 600 Km Australia 1910 1980 1910 1920 1890 1880 1870 1900

19. Copyright © 2009 Pearson Education, Inc. ECOSYSTEM STRUCTURE AND DYNAMICS

20. Copyright © 2009 Pearson Education, Inc. 37.14 Ecosystem ecology emphasizes energy flow and chemical cycling  Ecosystem –All the organisms in a community as well as the abiotic environment  Components of ecosystems –Energy flow –Passage of energy through the ecosystem –Chemical cycling –Transfer of materials within the ecosystem

21. Copyright © 2009 Pearson Education, Inc.  A terrarium has the components of an ecosystem 37.14 Ecosystem ecology emphasizes energy flow and chemical cycling

22. Energy flow Light energy Chemical energy Chemical elements Heat energy Bacteria and fungi Chemical cycling

23. Copyright © 2009 Pearson Education, Inc. 37.15 Primary production sets the energy budget for ecosystems  Primary production –The amount of solar energy converted to chemical energy –Carried out by producers –Produces biomass –Amount of living organic material in an ecosystem

24. Copyright © 2009 Pearson Education, Inc.  Primary production of different ecosystems 37.15 Primary production sets the energy budget for ecosystems

25. Open ocean Estuary Algal beds and coral reefs Desert and semidesert scrub Tundra Temperate grassland Cultivated land Boreal forest (taiga) Savanna Temperate deciduous forest Tropical rain forest 0 500 Average net primary productivity (g/m 2 /yr) 1,000 1,500 2,5002,000

26. Copyright © 2009 Pearson Education, Inc. 37.16 Energy supply limits the length of food chains  A pyramid of production –Illustrates the cumulative loss of energy transfer in a food chain

27. 1,000,000 kcal of sunlight 10 kcal 100 kcal 1,000 kcal 10,000 kcal Producers Primary consumers Secondary consumers Tertiary consumers

28. Copyright © 2009 Pearson Education, Inc. 37.17 CONNECTION: A production pyramid explains why meat is a luxury for humans  The dynamics of energy flow apply to the human population

29. Producers Primary consumers Secondary consumers Human meat-eaters Cattle Corn Human vegetarians Trophic level