2. Copyright © 2009 Pearson Education, Inc. COMMUNITY STRUCTURE AND DYNAMICS

3. Copyright © 2009 Pearson Education, Inc. ◦ Biological community –An assemblage of populations living close enough together for potential interaction –Described by its species composition ◦ Boundaries of the community vary with research questions –What kind of communities exist at Miramar College?

4. Copyright © 2009 Pearson Education, Inc. ◦ Interspecific interactions –Relationships with other species in the community –Can have positive (+) or negative (-) effects on each species

5. Copyright © 2009 Pearson Education, Inc. 1. Interspecific competition (usually -/- ) –Two different species compete for the same limited resource –Squirrels and black bears Bear and Squirrel by ~magooey on deviantART

6. Copyright © 2009 Pearson Education, Inc. ◦ Competition occurs when ecological niche of species overlap –Ecological niche: Sum of an organism’s use of biotic and abiotic resources

7. Copyright © 2009 Pearson Education, Inc. 2. Mutualism: both populations benefit (+/+) ◦ Example: Reef-building corals –Photosynthetic dinoflagellates and heterotrophic cnidarian

8. Copyright © 2009 Pearson Education, Inc. 3. Predation: benefits the predator but kills prey (+/-)  However, can lead to evolutionary adaptation

9. Copyright © 2009 Pearson Education, Inc. 4. Herbivory is not usually fatal and leads to adaptation in plants (+/-) –Plants must expend energy to replace the loss  Plants have numerous defenses against herbivores –Spines and thorns –Chemical toxins

10. Copyright © 2009 Pearson Education, Inc. 5. A parasite lives on or in a host from which it obtains nourishment (+/-) –Internal parasites include nematodes and tapeworms –External parasites include aphids and mosquitos

11. Copyright © 2009 Pearson Education, Inc.  Pathogens are disease-causing parasites (+/-) –Pathogens can be bacteria, viruses, fungi, or protists

12. Copyright © 2009 Pearson Education, Inc.  Non-native pathogens can have rapid and dramatic impacts  Non-native pathogens can cause a decline of the ecosystem  Example: Snakehead fish

13. Copyright © 2009 Pearson Education, Inc.  Trophic structure –A pattern of feeding relationships consisting of several different levels  Food chain –Sequence of food transfer up the trophic levels

14. Copyright © 2009 Pearson Education, Inc.  Producers –Support all other trophic levels –Examples??

15. Copyright © 2009 Pearson Education, Inc.  Producers –Support all other trophic levels –Examples: –Phytoplankton and plants  Consumers –Heterotrophs –Primary consumers –Secondary consumers –Tertiary consumers –Quaternary consumers

16. Copyright © 2009 Pearson Education, Inc.  Producers –Support all other trophic levels  Consumers –Heterotrophs –Primary consumers –Secondary consumers –Tertiary consumers –Quaternary consumers  Detritivores and decomposers –Derive energy from dead matter and wastes

17. Plant A terrestrial food chain Producers Phytoplankton An aquatic food chain

18. Plant A terrestrial food chain Producers Phytoplankton An aquatic food chain Primary consumers Grasshopper Zooplankton

19. Plant A terrestrial food chain Producers Phytoplankton An aquatic food chain Primary consumers Grasshopper Zooplankton Secondary consumers Mouse Herring

20. Plant A terrestrial food chain Producers Phytoplankton An aquatic food chain Primary consumers Grasshopper Zooplankton Secondary consumers Mouse Herring Snake Tuna Tertiary consumers

21. Plant A terrestrial food chain Producers Phytoplankton An aquatic food chain Primary consumers Grasshopper Zooplankton Secondary consumers Mouse Herring Snake Tuna Tertiary consumers Hawk Killer whale Quaternary consumers Trophic level

23. Copyright © 2009 Pearson Education, Inc.  Food web –A network of interconnecting food chains Example: Mercury poisoning Producers (plants) Primary consumers Secondary and primary consumers Tertiary and secondary consumers Quaternary, tertiary, and secondary consumers

25. Copyright © 2009 Pearson Education, Inc.  Species diversity defined by two components 1. Species richness 2. Relative abundance A B

26. Copyright © 2009 Pearson Education, Inc.  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 Keystone absent

29. Copyright © 2009 Pearson Education, Inc.  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

30. Copyright © 2009 Pearson Education, Inc.  Invasive species: non-native species spreading beyond their point of introduction and causing environmental or economic damage  Example: Snakehead fish Invasive species can devastate communities

31. 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

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

33. Copyright © 2009 Pearson Education, Inc.  Introduction of rabbits in Australia Key Frontier of rabbit spread Origin: 1860 600 Km Australia 1910 1980 1910 1920 1890 1880 1870 1900

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

35. Copyright © 2009 Pearson Education, Inc.  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

36. Copyright © 2009 Pearson Education, Inc.  A terrarium has the components of an ecosystem Energy flow Light energy Chemical energy Chemical elements Heat energy Bacteria and fungi Chemical cycling

37. Copyright © 2009 Pearson Education, Inc.  Primary production –The amount of solar energy converted to chemical energy –Carried out by ________________ –Produces biomass –Amount of living organic material in an ecosystem

38. Copyright © 2009 Pearson Education, Inc.  Primary production of different ecosystems 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

39. Copyright © 2009 Pearson Education, Inc.  A pyramid of production –Illustrates the cumulative loss of energy transfer in a food chain 1,000,000 kcal of sunlight 10 kcal 100 kcal 1,000 kcal 10,000 kcal Producers Primary consumers Secondary consumers Tertiary consumers

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

41. Copyright © 2009 Pearson Education, Inc.  Biogeochemical cycles –Cycle chemicals between organisms (biotic) and the Earth (abiotic)  Decomposers play a central role in biogeochemical cycles Consumers Geologic processes Producers Decomposers Nutrients available to producers Abiotic reservoir 4 1 2 3

42. Copyright © 2009 Pearson Education, Inc.  Biotic: Carbon is basis of organic molecules  Abiotic: Carbon is found ___________  The return of CO 2 to the atmosphere by respiration closely balances its removal by photosynthesis

43. Photosynthesis Decomposers (soil microbes) Cellular respiration Detritus 4 1 2 3 5 Plants, algae, cyanobacteria Primary consumers Higher-level consumers Burning CO 2 in atmosphere Plant litter; death Wastes; death Decomposition Wood and fossil fuels

45. Copyright © 2009 Pearson Education, Inc.  Biotic: organisms require phosphorus for ___________.  Abiotic: No atmospheric component; abiotic resevoir found in rocks, soil

46. Animals 1 Plants Detritus Decomposers in soil Decomposition Phosphates in rock Weathering of rock Runoff Assimilation Phosphates in solution Phosphates in soil (inorganic) Precipitated (solid) phosphates Rock Uplifting of rock 6 3 2 4 5

47. Copyright © 2009 Pearson Education, Inc.  Biotic: Nitrogen is essential for ________.  Abiotic: Nitrogen found in air and soil  Nitrogen fixation converts N 2 to nitrogen used by plants –Carried out by some bacteria and cyanobacteria

48. Rhizobium in symbiosis Azotobacter Klebsiella some Clostridium Leguminous root nodules TEM of rhizobia in root nodule cell Nitrogen fixation

49. Nitrogen (N 2 ) in atmosphere 8 Plant Animal Assimilation by plants Organic compounds Organic compounds Death; wastes Denitrifiers Nitrates in soil (NO 3 – ) Detritus Decomposers Decomposition Nitrifying bacteria Ammonium (NH 4 + ) in soil Nitrogen fixation Nitrogen fixation Nitrogen-fixing bacteria in root nodules Free-living nitrogen-fixing bacteria and cyanobacteria 6 1 2 7 4 3 5

50. Copyright © 2009 Pearson Education, Inc.  Chemical cycling in an ecosystem depends on –The web of feeding –Relationships between plants, animals, and detritivores –Geologic processes  Altering an environment can cause severe losses in chemical cycling –Erosion –Acid rain

51. Decomposers Producer Energy flow Chemical cycling Herbivore (primary consumer) Carnivore (secondary consumer)