Chapter 5 How Ecosystems Work

1. Chapter 5How Ecosystems Work

2. Lake Victoria • Freshwater lake in Africa • Formerly home to ≈ 400 species of cichlids • 1960: Nile perch introduced • 1990: water hyacinth invaded • Today, ecological imbalance; why?

3. What Is Ecology? • Literally study of one’s “house” • Interactions • Two components • Biotic • Abiotic • Broadest biological field of study

4. Ecological Organization • Organism • Population • Community • Ecosystem • Landscape • Biosphere

5. Positive and Negative Feedback Loops • Feedback Loop • circular process • Positive Feedback Loop • change becomes more pronounced • Negative Feedback Loop • change is reduced or inhibited

6. Landscape Ecology • Studies the connections among ecosystems • Ecosystem engineers • Organisms that create or modify habitat • How are grizzly bears ecosystem engineers?

7. Goals Of Ecologists • Understand how ecosystems function • Make connections: landscape ecology • Connections among ecosystems • Grizzly Bears

8. Energy • Capacity or ability to do work • Flows through ecosystems • Why do organisms need energy? • Different kinds Potential energy Kinetic energy

9. First Law of Thermodynamics • Energy cannot be created or destroyed • Energy can be changed from one form to another

10. Second Law of Thermodynamics • When energy is changed from one form to another, some is degraded into heat • Heat is a less usable form of energy • Increases entropy in the universe

11. Ecosystem Composition • Producers • Consumers • Decomposers

12. Light energy Producers • Make their own food • Photosynthesis • Examples? 6CO2 + 6H2O + ------> C6H12O6 + 6O2

13. Consumers • Feed on other things • Herbivores • Carnivores • Omnivores • Detrivores

14. Decomposers • Break down dead organisms and waste products • Examples?

15. Energy Flow • Energy passes from one organism to the next • Trophic level: each step in this flow of energy • Food chain: straight path • Food web • Interconnected food chains • More realistic than food chain; why?

16. Food Chain

17. Biological Production • Net Primary Production: amount of plant mass generated by photosynthesis and that remains after cellular respiration • Biomass: total amount of organic matter • NPP is measured by tracking the changes in biomass over time (NPP = B2 –B1)

18. Food Web

19. Biogeochemical Cycles • Matter cycles through ecosystems • Five cycles • Carbon • Hydrologic (water) • Nitrogen • Sulfur • Phosphorus

20. Photosynthesis Cellular respiration CO2 Sugar CO2 Carbon Cycle • Essential component for life • Gas (CO2) in atmosphere • Several forms in ocean • Can take a long time—think fossil fuels

21. Carbon Cycle

22. Ocean Atmosphere Land Ocean Hydrologic Cycle

23. Nitrogen Cycle • Proteins, DNA • Atmosphere is 78% N2 • Five steps • Nitrogen fixation • Nitrification • Assimilation • Ammonification • Denitrification

24. Nitrogen Fixation • Specialized bacteria • Split atmospheric nitrogen and combine it with hydrogen

25. Nitrogen Cycle

26. Land Organism Organism Land Phosphorus Cycle • No atmospheric component • Phosphates used in DNA and ATP (chemical energy) • Phosphates move through the food chain

27. Phosphorus Cycle

28. Ecological Niche • Everything about an organism • Adaptations • Use of resources • Lifestyle • Habitat

29. Ecological Niche • Two species cannot occupy the same niche: why? • Resource partitioning • Reduces niche overlap • Reduces competition

30. Resource Partitioning At Work!

31. Species Interactions • No species lives in complete isolation • Symbiosis • Intimate relationship between members of at least 2 species • Mutualism, commensalism, parasitism • Result of coevolution • Other interactions • Predation, competition

32. Mutualism • Both species benefit

33. Commensalism • One species benefits, other not affected

34. Parasitism • Parasite benefits, host is “harmed” • Ectoparasites & endoparasites

35. Species Interactions • Predation: consumption of one species by another • Coevolution: “arms race”

36. Avoiding Predators • Mechanical defenses • Social groups • Camouflage • Protective chemicals

37. Species Interactions • Competition: two or more organisms attempting to use the same resource • Intraspecific vs. interspecific

38. Keystone Species • Crucial to maintenance of an ecosystem • Loss affects many other species • Examples? • What are the differences between a keystone, umbrella or flagship species?

39. Adaptive EcosystemManagement • Ecosystem Management: meeting the goals or objectives of the biotic community and their associated abiotic components • Adaptive Ecosystem Management: • developed by C.S. Holling and Carl J. Walters, University of B.C., 1970 • acknowledges the uncertainty and the need for managers to learn while they manage • passive and active

40. Eco Canada Career Focus • Consider a career as an ecologist • Ecologists study the relationships between living things and their environments

41. Case Study: Human Appropriation of Net Primary Productivity (HANPP) • HANPP : indicator of are of land an the amount of biomass consumed by humans • Valuable indicator of “human domination of ecosystems” on a global scale • Many countries are consuming an excess of 100% of locally available NPP

42. Case Study: Human Appropriation of Net Primary Productivity (HANPP)