Community ecology


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PowerPoint to accompany Ch 54 Community Ecology of Biology [8e] by Campbell & Reece.

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  • bottom is a milk snake (not poisonous), top is coral snake (very poisonous)
  • Parasites can affect reproduction, survival, density. Mechanical parasites (cloud forests epiphytes) Coral reefs usually occur in nutrient poor waters and must be shallow enough for sunlight to reach them. Contained between the cells of the coral polyp cylinder are single-celled green algae called dinoflagellates. The coral polyp and the dinoflagellates form a complex mutualistic relationship. The coral polyp sweeps organic material from the water and metabolizes this material forming carbon dioxide and nitrogenous wastes. The dinoflagellates use the carbon dioxide and nitrogenous wastes in photosynthesis to form oxygen and sugars that are in turn used by the coral polyps as well as the dinoflagellates in their metabolism, reforming the carbon dioxide and nitrogenous wastes. This cyclical exchange of nutrients, oxygen, and carbon dioxide is beneficial to both the coral polyps and the dinoflagellates, a mutualistic relationship. (
  • Community ecology

    1. 1. Community Ecology Chapter 54 Jeff Jewett American College of Sofia Version 1.0 May 20 th , 2010
    2. 2. Community <ul><li>A group of populations (each population is one species) living close enough together to interact </li></ul>
    3. 3. Interspecific Interactions <ul><li>Occur between individuals of DIFFERENT species </li></ul><ul><li>Competition - /- </li></ul><ul><li>Predation / Herbivory +/ - </li></ul><ul><li>Symbiosis </li></ul><ul><ul><li>Parasitism +/- </li></ul></ul><ul><ul><li>Commensalism +/0 </li></ul></ul><ul><ul><li>Mutualism +/+ </li></ul></ul>
    4. 4. Interspecific Competition (- / - ) Russian Ecologist G.F. Gause 1934 (Image from: <ul><li>2 or more different species competing for same resource (food, habitat, water, protection, etc.) </li></ul><ul><li>Ecological Niche : “sum of a species use of the biotic and abiotic resources in its environment” </li></ul><ul><li>Habitat = “address,” niche = “profession” </li></ul>Competitive Exclusion Virtual Lab
    5. 5. Competitive Exclusion Principle <ul><li>2 species cannot occupy the same niche in same community at the same time </li></ul><ul><li>One will win, the other will die, migrate, or adapt </li></ul><ul><li>C.E.P. leads to Resource Partitioning </li></ul>
    6. 6. Resource Partitioning <ul><li>“Peace treaties” </li></ul>
    7. 7. Interspecific Competition, Continued <ul><li>Resource Partitioning – differentiation of niches to allow similar species to coexist in a community (space, behavior, temporal) </li></ul><ul><li>Fundamental niche – the niche a species could theoretically occupy, without competitors </li></ul><ul><li>Realized niche – the niche a species actually occupies, with competitors </li></ul>
    8. 8.
    9. 11. <ul><li>Body changes as a result of resource partitioning </li></ul>Character Displacement
    10. 12. Galapagos Finches These birds show character displacement due to resource partitioning.
    11. 13. Predation <ul><li>Includes herbivory </li></ul><ul><ul><li>plants have defense chemicals, spines, thorns </li></ul></ul><ul><li>Predators: binocular vision, prey: monocular vision </li></ul><ul><li>Camouflage </li></ul><ul><li>Mimicry </li></ul><ul><li>Warning (“aposematic”) coloration </li></ul><ul><li>Predator-Prey Animation (NortonBooks) </li></ul> DANGER!
    12. 14. Photo: Dr. Shannon Savage, 2007 Count the toads….
    13. 15. Predator? Prey? Look at the eyes! (Well, and that beak…)
    14. 16. Symbiosis <ul><li>“ living together” </li></ul><ul><li>Parasitism (+/-) </li></ul><ul><li>Commensalism (+/o) – rare </li></ul><ul><li>Mutualism (+/+) win-win! (Lichen, Coral, digestive bacteria, mycorrhizae on plant roots) </li></ul> лишей
    15. 17. Commensal Interactions (+/0) <ul><li>Epiphytes (?) </li></ul><ul><li>Whales/barnacles (?) </li></ul><ul><li>Clownfish/Anemone (?) </li></ul>
    16. 18. 54.2 Species Diversity <ul><li>What makes a healthy ecosystem? </li></ul><ul><li>Species richness (# species) </li></ul><ul><li>Relative abundance (proportion) </li></ul>
    17. 19. Food Webs
    18. 20. Species with a large impact <ul><li>Dominant Species – most abundant, or most biomass </li></ul><ul><li>Keystone Species – important niches (pollinators, top predators) </li></ul><ul><li>Ecosystem Engineers – change the environment (humans, beavers, elephants) </li></ul>
    19. 21. Keystone Species – Seastars ( Pisaster ochraceus )
    20. 22. Keystone Species – Sea Otter
    21. 23. <ul><li>Regulates snowmelt runoff </li></ul><ul><li>Reduces soil erosion </li></ul><ul><li>Facilitates other plant growth </li></ul><ul><li>FOOD! – squirrels, birds, bears </li></ul>Pinus Albicaulis : Subalpine keystone species
    22. 24. 54.3 Disturbance & Succession <ul><li>Disturbance – an event that changes a community by removing organisms or altering resource availability </li></ul><ul><li>Fire, storm, human activity, drought, overgrazing, flood </li></ul>
    23. 25. Disturbance & Succession <ul><li>Primary Succession </li></ul><ul><li>Secondary Succession (ACS Campus) </li></ul><ul><li>Climax Community </li></ul><ul><li>Non-equilibrium model (everything’s always changing!) </li></ul><ul><li>Intermediate disturbance hypothesis </li></ul>
    24. 26. Primary Succession <ul><li>Mosses and lichens create soils in this example of primary succession from Yosemite National Park, CA. </li></ul><ul><li>The valley emerged ~10,000 years ago after being scraped clean by a glacier </li></ul><ul><li>Grasses, shrubs and even trees appear where soil has slowly developed. </li></ul>
    25. 27. The steep hillsides show early stages of primary succession (little or no soil), but the low, flat places accumulate soil and support grasses/trees. (Yosemite National Park, CA.)
    26. 28. Secondary Succession Yosemite National Park, CA . After a wildfire, grasses and tree seedlings grow up to replace the burned forest.
    27. 29. Secondary Succession Yosemite National Park, CA . Later after a wildfire, shrubs and short trees grow up to replace the burned forest. A few gray snags of the old burned forest are still visible.
    28. 30. Pond Succession
    29. 31. Biogeography & Community Diversity <ul><li>Hot & wet = more species (rainforests!) </li></ul><ul><li>Equatorial regions – more than polar or temperate (older, friendlier climate) </li></ul><ul><li>Larger area – support a higher number of species </li></ul>