Biological Communities And Interaction

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Biological Communities And Interaction

  1. 1. Biological Communities and Species Interaction
  2. 2. Important Concepts: <ul><li>Critical Environmental Factors </li></ul><ul><li>Adaptation </li></ul><ul><li>Natural Selection </li></ul><ul><li>Speciation </li></ul><ul><li>Ecological Niche </li></ul><ul><li>Population Dynamics </li></ul><ul><li>Community Properties </li></ul><ul><li>Succession </li></ul><ul><li>Introduced Species </li></ul>
  3. 3. Types of Species Interactions <ul><li>Competition </li></ul><ul><li>Predation – Trophic levels </li></ul><ul><li>Mutualism </li></ul><ul><li>Community Structure </li></ul><ul><li>Succession </li></ul>
  4. 4. Critical Environmental Factors <ul><li>Single factor in shortest supply relative to demand is the critical determinant in species distribution. </li></ul><ul><li>Each environmental factor has both minimum and maximum levels, tolerance limits, beyond which a particular species cannot survive. </li></ul><ul><ul><li>No humans permanently above 5 km </li></ul></ul>
  5. 5. Tolerance Limits
  6. 6. Limits of Range <ul><li>Physical Barriers </li></ul><ul><ul><li>Oceans (humans, cattle egrets, marsupials) </li></ul></ul><ul><ul><li>Mountains (house finch) </li></ul></ul><ul><ul><li>Ice (humans in the Americas) </li></ul></ul><ul><li>Climatic </li></ul><ul><li>Altitude </li></ul><ul><li>Food </li></ul><ul><li>Water </li></ul><ul><li>Competitors </li></ul>
  7. 7. Expanding Human Range
  8. 8. Critical Environmental Factors <ul><li>For many species, the interaction of several factors, rather than a single limiting factor, determines biogeographical distribution. </li></ul><ul><ul><li>Altitude = oxygen, temperature, food </li></ul></ul><ul><ul><li>May be a specific critical factor that mostly determines abundance and distribution. </li></ul></ul><ul><li>Species requirements and tolerances can also be used as useful indicators. </li></ul><ul><ul><li>Environmental indicators </li></ul></ul>
  9. 9. Adaptation <ul><li>Adaptation is used in two ways: </li></ul><ul><li>Individual (moving from one place to another) </li></ul><ul><li>Population (evolution) </li></ul>
  10. 10. Natural Selection <ul><li>Natural Selection - Members of a population best suited for a particular set of environmental conditions survive and produce offspring more successfully than their competitors. </li></ul><ul><ul><li>Acts on pre-existing genetic diversity. </li></ul></ul><ul><ul><li>Limited resources place selective pressures on a population. </li></ul></ul>
  11. 11. Speciation <ul><li>Given enough geographical isolation or selective pressure, members of a population become so different from their ancestors that they may be considered an entirely new species. </li></ul><ul><li>Alternatively, isolation of population subsets, preventing genetic exchange, can result in branching off of new species that coexist with the parental line. </li></ul>
  12. 12. Divergent vs. Convergent Evolution <ul><li>Divergent Evolution - Mutations and different selective pressures cause populations to evolve along dissimilar paths. </li></ul><ul><li>Convergent Evolution - Unrelated organisms evolve separately to cope with environmental conditions in the same fashion. </li></ul><ul><ul><li>Look alike - Act alike </li></ul></ul><ul><ul><li>Usually means some physical basis </li></ul></ul>
  13. 13. Divergent evolution
  14. 14. Convergent evolution
  15. 15. Parallel Evolution <ul><li>two related species arise from a common ancestor. The two species then evolve in much the same way over time, probably in response to similar environmental selection pressures. </li></ul>
  16. 16. Ecological Niche <ul><li>Habitat - Place or set of environmental conditions where a particular organism lives. </li></ul><ul><li>Ecological Niche </li></ul><ul><ul><li>Role a species plays in a biological community (e.g. large grassland herbivore) </li></ul></ul><ul><ul><li>Total set of environmental factors that determines a species’ distribution. </li></ul></ul><ul><ul><li>Generalists - Broad niche </li></ul></ul><ul><ul><li>Specialists - Narrow niche </li></ul></ul><ul><li>When generalists and specialists collide, generalists usually win. </li></ul>
  17. 17. Generalist species Tree sparrows Yellow vented bulbul
  18. 18. Specialist species Philippine frogmouth
  19. 19. Philippine Eagle Silvery kingfisher
  20. 20. Competition
  21. 21. Law of Competitive Exclusion <ul><li>No two species will occupy the same niche and compete for exactly the same resources for an extended period of time. </li></ul><ul><li>One will either migrate, become extinct, or partition the resource and utilize a sub-set of the same resource. </li></ul><ul><li>Given resource can only be partitioned a finite number of times. </li></ul>
  22. 22. Resource Partitioning
  23. 23. Predation <ul><li>Feeds directly upon another living organism, whether or not it kills the prey in doing so. </li></ul><ul><ul><li>Mosquitoes prey on humans </li></ul></ul><ul><li>Prey most successfully on slowest, weakest, least fit members of target population. </li></ul><ul><ul><li>Reduce competition, population overgrowth, and stimulate natural selection. </li></ul></ul><ul><ul><li>Co-evolution (arms race) </li></ul></ul>
  24. 24. Co-Evolution and Disease <ul><li>If a disease kills too quickly, it can’t spread </li></ul><ul><li>Disease can moderate while host becomes more resistant (measles) </li></ul><ul><li>Disease can be lethal but messy (cholera, ebola) </li></ul><ul><li>Disease can be lethal but slow-acting (AIDS) </li></ul>
  25. 25. Keystone Species <ul><li>Keystone Species - A species or group of species whose impact on its community or ecosystem is much larger and more influential than would be expected from mere abundance. </li></ul><ul><ul><li>Large predators ( tigers, Phil. Eagle) </li></ul></ul><ul><ul><li>Critical food organisms (bamboo and pandas) </li></ul></ul><ul><ul><li>( eucalyptus & koala) </li></ul></ul><ul><ul><li>Often, many species are intricately interconnected so that it is difficult to tell which is the essential component. </li></ul></ul>
  26. 26. Competition <ul><li>Interspecific - Competition between members of different species. </li></ul><ul><li>Intraspecific - Competition among members of the same species. </li></ul><ul><ul><li>Often intense due to same space and nutritional requirements. </li></ul></ul><ul><ul><ul><li>Territoriality - Organisms defend specific area containing resources, primarily against members of own species. </li></ul></ul></ul><ul><ul><ul><li>Resource Allocation and Spacing </li></ul></ul></ul>
  27. 27. Mutualism <ul><li>Intimate living together of members of two or more species. </li></ul><ul><li>Commensalism - One member benefits while other is neither benefited nor harmed. </li></ul><ul><ul><li>Cattle and Cattle Egrets </li></ul></ul><ul><li>Symbiosis - Both members benefit. </li></ul><ul><ul><li>Lichens (Fungus and cyanobacterium) </li></ul></ul><ul><li>Parasitism - One member benefits at the expense of other. </li></ul><ul><ul><li>Humans and Tapeworms </li></ul></ul>
  28. 28. Commensalism: Epiphytes:
  29. 29. Symbiosis - Lichens
  30. 30. Defensive Mechanisms <ul><li>Batesian Mimicry - Harmless species evolve characteristics that mimic unpalatable, dangerous or poisonous species </li></ul><ul><ul><li>Viceroy and Monarch butterfly </li></ul></ul><ul><li>Mullerian Mimicry - Two unpalatable species evolve to look alike </li></ul><ul><ul><li>Bees and Wasps </li></ul></ul><ul><li>Camouflage </li></ul><ul><li>Advertising and warning (coral snake) </li></ul><ul><li>Attracting prey, pollinators, mates, etc. </li></ul>
  31. 31. Abundance and Diversity <ul><li>Abundance -Total number of organisms in a community. </li></ul><ul><li>Diversity - Number of different species, ecological niches, or genetic variation. </li></ul><ul><ul><li>Abundance of a particular species often inversely related to community diversity. </li></ul></ul><ul><ul><li>As general rule, diversity decreases and abundance within species increases when moving from the equator to the poles. </li></ul></ul>
  32. 32. Productivity <ul><li>Primary Productivity - Rate of biomass production. Rate of solar energy conversion to chemical energy. </li></ul><ul><ul><li>Net Primary Productivity - Energy left after metabolism </li></ul></ul><ul><ul><li>Highest in rain forest, estuaries, reefs </li></ul></ul><ul><ul><li>Decreases toward poles </li></ul></ul><ul><ul><li>Open oceans very low </li></ul></ul>
  33. 33. Trophic Level (Food Chain) <ul><li>A pond </li></ul><ul><ul><li>Phytoplankton </li></ul></ul><ul><ul><li>Zooplankton </li></ul></ul><ul><ul><li>Small Fish </li></ul></ul><ul><ul><li>Larger Fish </li></ul></ul><ul><ul><li>Higher predators (birds, mammals) </li></ul></ul><ul><li>Organisms are at same trophic level if they get their food from similar sources </li></ul>
  34. 34. Trophic Level (Food Chain) <ul><li>A forest </li></ul><ul><ul><li>Decaying organic matter </li></ul></ul><ul><ul><li>Insects </li></ul></ul><ul><ul><li>Small mammals and birds </li></ul></ul><ul><ul><li>Higher predators (owls, foxes, bears) </li></ul></ul><ul><li>A Pasture or Grassland </li></ul><ul><ul><li>Grass </li></ul></ul><ul><ul><li>Herbivore </li></ul></ul><ul><ul><li>Higher predators </li></ul></ul>
  35. 35. Trophic Level (Food Chain) <ul><li>At each level, some matter goes into biomass </li></ul><ul><li>Most goes into energy and metabolism </li></ul><ul><li>Hence each level needs about 10x as much energy, has fewer individuals </li></ul><ul><li>Bio-Accumulated chemicals get more abundant higher up the food chain </li></ul>
  36. 36. Food Requirements <ul><li>Warm-blooded organisms require more food than cold-blooded </li></ul><ul><ul><li>Predator/prey ratio higher for cold-blooded </li></ul></ul><ul><ul><li>Indication that some dinosaurs may have been warm-blooded </li></ul></ul><ul><li>Large organisms eat less in proportion to their mass than small ones </li></ul><ul><ul><li>Shrew: 100%+ per day </li></ul></ul><ul><ul><li>Human: 1% per day </li></ul></ul>
  37. 37. Improbable Movie Biology <ul><li>Things that eat people (Morlocks, The Time Machine ) </li></ul><ul><li>Really huge carnivores ( The Phantom Menace ) </li></ul><ul><li>Huge carnivores in empty environments ( Empire Strikes Back , Return of the Jedi ) </li></ul><ul><li>Ultra-voracious carnivores ( Jaws, Alien, Anaconda, Jurassic Park ) </li></ul>
  38. 38. Complexity and Connectedness <ul><li>Complexity - Number of species at each trophic level, and the number of trophic levels, in a community. </li></ul><ul><ul><li>Diverse community may not be complex if all species are clustered in a few trophic levels. </li></ul></ul><ul><ul><li>Highly interconnected community may have many trophic levels, some of which can be compartmentalized. </li></ul></ul>
  39. 39. Resilience and Stability <ul><li>Constancy (Lack of fluctuation) </li></ul><ul><li>Inertia (Resistance to pertubation) </li></ul><ul><li>Renewal (Ability to repair damage) </li></ul><ul><ul><li>MacArthur proposed complex, interconnected communities would be more stable and resilient in the face of disturbance. </li></ul></ul><ul><ul><ul><li>Controversial </li></ul></ul></ul>
  40. 40. Edges and Boundaries <ul><li>Edge Effects - Important aspect of community structure is the boundary between one habitat and others. </li></ul><ul><li>Ecotones - Boundaries between adjacent communities. </li></ul><ul><ul><li>Sharp boundaries - Closed communities </li></ul></ul><ul><ul><li>Indistinct boundaries - Open communities </li></ul></ul>
  41. 41. COMMUNITIES IN TRANSITION <ul><li>Ecological Succession </li></ul><ul><ul><li>Primary Succession - A community begins to develop on a site previously unoccupied by living organisms. </li></ul></ul><ul><ul><ul><li>Pioneer Species </li></ul></ul></ul><ul><ul><li>Secondary Succession - An existing community is disrupted and a new one subsequently develops at the site. </li></ul></ul>
  42. 42. Terrestrial Primary Succession
  43. 43. Ecological Succession <ul><li>Ecological Development - Process of environmental modification (facilitation) by organisms. </li></ul><ul><li>Climax Community - Community that develops and seemingly resists further change. </li></ul><ul><ul><li>Equilibrium Communities (Disclimax Communities) - Never reach stable climax because they are adapted to periodic disruption. </li></ul></ul>
  44. 44. Introduced Species <ul><li>If introduced species prey upon or compete more successfully than native populations, the nature of the community may be altered. </li></ul><ul><ul><li>Human history littered with examples of introducing exotic species to solve problems caused by previous introductions. </li></ul></ul><ul><ul><ul><li>Mongoose and Rats in Caribbean </li></ul></ul></ul>
  45. 45. Summary: <ul><li>Critical Environmental Factors </li></ul><ul><li>Adaptation </li></ul><ul><li>Natural Selection </li></ul><ul><li>Speciation </li></ul><ul><li>Ecological Niche </li></ul><ul><li>Population Dynamics </li></ul><ul><li>Community Properties </li></ul><ul><li>Succession </li></ul><ul><li>Introduced Species </li></ul>

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