Understanding Ecosystems: Importance and Ecological Interactions

1. Ecology Chapters 57 - 58 Why knowing about ecosystems is important? Scientific knowledge as ‘models’ Basic ecological concepts Biotic interactions in an ecosystem Ecosystem structure Ecosystem dynamics Ecology

2. Why understanding ecosystems is important DDT (dichloro-diphenyl-trichloroethane) 1874: discovery 1934: Paul Müller, Swiss chemist “polychlorinated hydrocarbon” DDT is a potent insecticide ... Low toxicity for humans (mammals) Many Agricultural uses e.g., corn earworm, cotton bollworm tobacco budworms Control of diseases malaria, typhus WWII Dutch elm disease Cotton bollworm Ecology

3. By the 1950s other people were seeing other, unintended effects . . . Fish -- trout, sunfish, suckers, etc -- higher toxicity than to mammals Birds of prey -- eagles, osprey, hawks, etc -- Reproductive effects Songbirds What was impact of Rachel Carson’s “Silent Spring”? -- 1962 Tranforms U.S. environmental consciousness Nat. Envr. Prot. Act (NEPA) CAA & CWA DDT banned in 1973 Ecology

4. Why did we misjudge effects of DDT? An incomplete understanding of ecosystems . . . • How do organisms interact with their surroundings? • How do organisms interact with each other? • How do nutrients (and pollutants) move & change in an ecosystem? • How do ecosystems change over time? Our answers to these form a ‘model’ of ecosystem function What is a scientific ‘model’? How does it differ from traditional ‘fact-based’ knowledge? 1) Recognized to be incomplete 2) simplified version of reality 3) explain all current information 4) are modified over time Ecology

5. A ‘food chain’ and ‘food web’ illustrate two models with different levels of detail Ecology

6. What is an Ecosystem? “a community of organisms and the environment with which they interact” An ecosystem includes: Biotic components Abiotic components Organisms interact, and interact with the abiotic components Ecology

7. How big is an ecosystem? Depends on model being studied . . biomes forests bodies of water organisms -- human microbiota microecosystems Why are ecosystems said to be “open systems”? Ecology

8. Characteristics of the Abiotic components What are some examples of abiotic factors? What is meant by: Environment? Climate? Range? Habitat? Coral Reef Ecology

9. Characteristics of the Biotic components What is a : Species? Population? Community? Ecology

10. The population of each species has a particular age structure that reflects the species survivorship curve Type I Type II Type III Ecology

11. The size of populations change and cycle over time Why? e.g., central European larch bud moth -- periodic outbreaks every 8-10 years Ecology

12. Unstable human populations have a pyramidal age structure = rapid population growth Human population has been growing exponentially What will be the consequence of continued human population growth? Ecology

13. Communities can be simple or very complex What is “Biodiversity”? What factors influence diversity? -- productivity -- climate -- habitat heterogeneity -- # of other species Diversity ‘hot spots’ Ecology

14. Species within an ecosystem interact with each other Competition Predator-prey Symbiosis Competition What are two forms of competition? Intraspecific competition Interspecific competition Ecology

15. Each species exists within a particular ecological niche -- encompasses both biotic and abiotic factors Ecological niche = “All the abiotic and biotic resources a species can use. ” What is a ‘fundamental’ niche? -- theoretical ‘realized’ niche? -- actual -- due to competition Ecology

16. Can two species exist in the same ecological niche? The “Competitive Exclusion Principle” says No. Classic Paramecium experiment Evolution causes species to avoid competitive exclusion “Resource Partitioning” e.g. Caribbean anoles Ecology

17. Predator-Prey relationships An ongoing evolutionary “one upmanship” game Many animal defense mechanisms Vigilance, e.g., Flocking ostriches Concealment, e.g., Chuckwalla lizard Camouflage (cryptic coloration) Warning Coloration, e.g., Skunk Ecology

18. Animal defense mechanisms, con’t Mimicry Batesian mimicry Müllerian mimicry How are mimicry and cryptic coloration different? Ecology

19. Some other really neat defense mechanisms. . . Ecology

20. Predators evolve strategies also Predators and prey “co-evolve’ Angler fish Snake Common stargazer fish Ecology

21. What are the types of symbiosis? Mutualism Commensalism Parasitism vs Parasitoidism external internal These relationships are not always what they seem… Ecology

22. What type of symbiosis does each of these relationships represent? How is each organism benefited or harmed? Rhino and tick bird Mistletoe on pine Ecology

23. Let’s test our knowledge… Symbiosis Question Defense mechanisms Question 1 Question 2 Types of Mimicry Question Ecology

24. “Clumped” Ecological interactions determine how species are distributed -- within the Range vs within a Population (from chapter 55.2) There are three types of dispersal? What factors determine how individuals are distributed? -- interactions within species and between species -- resource distribution You are not responsible for: -- logistic growth curve equation -- r & k selected species Ecology

25. Ecosystems change over geographic space Community changes over a gradient of habitat Create an “Ecotone” Ecology

26. Ecosystems change over time -- called ‘Succession” Primary vs secondary succession pioneer species climax community Why does succession occur? Ecology

27. Secondary Succession Disturbances -- Fire in Yellowstone Ecology

28. Old Field Succession Ecology

29. All organisms require Energy and Nutrients Energy and Nutrients “flow” through ecosystems along food chains What is the source of all energy? What are the sources of nutrients? Carbon: Other nutrients (K, P, Mg, Ca, S, Fe, etc) The different steps of a food chain are called Trophic Levels Ecology

30. Organisms are classified as Autotrophs or Heterotrophs based upon their sources of Energy and Nutrients Autotrophs: E: N: Heterotrophs E: N: Ecology

31. There are three types of “ecological pyramids” What does each show? Energy Numbers Biomass (weight of organisms) ----> amount of nutrients Inverted pyramids? Ecology

32. What happens to the energy as it passes through an ecosystem? All energy is lost as heat Byproduct of metabolism -- particularly for endothermic animals Ecology

33. How much energy passes from trophic level to trophic level? This is why food chains are usually relatively short Ecology

34. What happens to nutrients? Ecology

35. How do nutrients flow through ecosystems? -- Biogeochemical Cycles Carbon cycle Nitrogen cycle Ecology

36. Do all essential nutrients flow through biogeochemcal cycles? Limiting nutrients Key steps of The N cycle Roles of Microorganisms Plants Animals Environmental issues Note: you are not responsible for the individual steps of the phosphorus cycle, but should have a general understanding of the role of P-related issues. Ecology

37. DDT Bioaccumulates in food chains Which types of pollutants will tend to bioaccumulate? See page 1227 Question Ecology

38. How well can ecosystems withstand disruptions? Very well …. But only for certain changes changes Food chains are simplified models -- Food webs are more complete representation Food webs are resilient -- redundancy Ecology

39. Disruptions at one trophic level affect organisms in adjoining levels Consider Kangaroo rate experiment in book Rats excluded from plots of desert Had effects on harvester ants -- rats and ants do not directly interact -- but they share food sources How and why did ant populations change? Ecology

40. Disruptions can reverberate up or down trophic levels? Top down effects Elimination of wolves caused loss of aspen (restored) Bottom-up effects Disruption of producers Human impacts Adadpted from Ripple WJ and Bescht RL (2007) Restoring Yellowstone’s aspen with wolves. Biological Conseravation 138: 514-519 http://www.cof.orst.edu/leopold/papers/Restoring%20Yellowstone%20aspen%20with%20wolves.pdf Ecology

41. Introduction of invasive species can disrupt an ecosystems Why? Examples: Zebra mussels Japanese knotweed Purple loosestife Emerald Ash Borer Ecology

42. Short term changes in weather can disrupt ecosystems In 1997, ~500,000 short-tailed shearwater birds were found dead in the Bering Sea off Alaska. What happened? Change in weather pattern favored Ehux Ecology

43. Anthropogenic Climate Change is of great concern What’s the evidence? Lots . . . What’s the effect? Disruption of “phenology” & ecological interactions Habitat loss and change Ecology

44. Declinse in “keystone “ species can have most devastating effects What is a “Keystone species”? e.g., Octopus e.g., CA sea otter Importance to Kelp Forests Conflicts with shellfish industry -- crabs, abalone Surge of sea urchins Ecology