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Community ecology


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Community ecology

  1. 1. Community Ecology
  2. 2. Communities <ul><li>A community is a group of organisms of different species that live in a particular area </li></ul>
  3. 3. Individualistic Hypothesis vs. Interactive Hypothesis <ul><li>Individualistic Hypothesis: </li></ul><ul><ul><li>A community is a chance group of species found in the same area because they have similar abiotic requirements </li></ul></ul><ul><li>Interactive Hypothesis: </li></ul><ul><ul><li>A community is a group of closely linked species locked together in mandatory biotic interactions that cause the community to function as an integrated unit </li></ul></ul>
  4. 4. Interspecific Interactions <ul><li>Inter specific interactions are interactions that occur between populations of different species living together in a community </li></ul><ul><li>There are 4 major interspecific interactions: </li></ul><ul><ul><li>Predation (and parasitism) </li></ul></ul><ul><ul><li>Competition </li></ul></ul><ul><ul><li>Commensalism </li></ul></ul><ul><ul><li>Mutualism </li></ul></ul>
  5. 5. Predation (and Parasitism) <ul><li>(+ -) </li></ul><ul><ul><li>The interaction is beneficial to one species and detrimental to the other </li></ul></ul><ul><li>Predation: </li></ul><ul><ul><li>When a predator eats its prey </li></ul></ul><ul><ul><li>Example in picture: </li></ul></ul>
  6. 6. Predation (and Parasitism) <ul><li>Parasitism: </li></ul><ul><ul><li>Predators that live on or in their hosts, usually feeding off their body tissues or fluids </li></ul></ul><ul><ul><ul><li>Usually do not kill their hosts </li></ul></ul></ul><ul><ul><li>Examples: </li></ul></ul>
  7. 7. Plant Defenses Against Herbivores <ul><li>“ Plants Fight Back!” </li></ul><ul><li>Plants have 2 major mechanisms by which they defend themselves against being eaten </li></ul><ul><ul><li>Mechanical Defenses </li></ul></ul><ul><ul><ul><li>Thorns, hooks, etc. </li></ul></ul></ul>
  8. 8. Plant Defenses Against Herbivores <ul><li>Chemical Defenses </li></ul><ul><ul><li>Produce chemicals that are distasteful or harmful to an herbivore </li></ul></ul><ul><ul><li>Morphine (opium poppy) </li></ul></ul><ul><ul><li>Nicotine (tobacco) </li></ul></ul>
  9. 9. Animal Defenses Against Predators <ul><li>Animals defend themselves against predators passively (hiding) or actively (fleeing) </li></ul><ul><li>Cryptic coloration (camouflage) makes prey difficult to spot </li></ul>
  10. 10. Animal Defenses Against Predation <ul><li>Mimicry </li></ul><ul><ul><li>When one species “imitates” or “mimics” another </li></ul></ul><ul><ul><li>Batesian mimicry </li></ul></ul><ul><ul><ul><li>When one edible or harmless species mimics an bad-tasting (unpalatable) or harmful species </li></ul></ul></ul><ul><ul><ul><li>Example: hawkmoth mimics a snake </li></ul></ul></ul>
  11. 11. Animal Defenses Against Predation <ul><li>Mimicry </li></ul><ul><ul><li>Mullerian mimicry </li></ul></ul><ul><ul><ul><li>Two species, both of which are unpalatable (taste bad) or harmful, resemble each other </li></ul></ul></ul><ul><ul><ul><li>Example: monarch butterfly (unpalatable) and queen butterfly (unpalatable) resemble each other </li></ul></ul></ul>
  12. 12. Parasitism <ul><li>One organism (the parasite) gets its nourishment from another organism (the host), which is harmed in the process </li></ul><ul><li>Endoparasites: </li></ul><ul><ul><li>Live within host tissues (tapeworms) </li></ul></ul><ul><li>Ectoparasites: </li></ul><ul><ul><li>Feed on external surfaces (mosquitoes) </li></ul></ul>
  13. 13. Interspecific Competition <ul><li>Competition between organisms of different species </li></ul><ul><li>The Competitive Exclusion Principle: </li></ul><ul><ul><li>Two species with similar needs for the same limiting resources cannot coexist in the same place </li></ul></ul>
  14. 15. Ecological Niches <ul><li>An organism’s niche is the specific role it plays in its environment </li></ul><ul><ul><li>All of its uses of biotic and abiotic resources in its environment </li></ul></ul><ul><ul><li>Example: oak tree in a deciduous forest </li></ul></ul><ul><ul><ul><li>Provides oxygen to plants, animals, etc. </li></ul></ul></ul><ul><ul><ul><li>Home for squirrels </li></ul></ul></ul><ul><ul><ul><li>Nesting ground for blue jays </li></ul></ul></ul><ul><ul><ul><li>Takes water out of the soil </li></ul></ul></ul><ul><ul><ul><li>Etc., etc. </li></ul></ul></ul>
  15. 16. Commensalism <ul><li>(+0) relationship </li></ul><ul><li>One partner benefits, the other is not affected </li></ul><ul><li>Examples: </li></ul><ul><ul><li>Cattle and cattle egret (birds) </li></ul></ul><ul><ul><li>Sea anemone and clownfish </li></ul></ul><ul><ul><ul><li>Clownfish gets a place to live, sea anemone is not affected </li></ul></ul></ul>
  16. 17. Mutualism <ul><li>(++) relationship </li></ul><ul><li>Both partners benefit from the relationship </li></ul><ul><li>“ You scratch my back, I’ll scratch yours” </li></ul><ul><li>Examples: </li></ul><ul><ul><li>Mycorrhizae </li></ul></ul><ul><ul><ul><li>Plant gets increased water/nutrition, fungi gets food </li></ul></ul></ul><ul><ul><li>Hummingbirds & flowers </li></ul></ul><ul><ul><ul><li>Hummingbirds get food, flowers can reproduce </li></ul></ul></ul>
  17. 18. Dominant & Keystone Species <ul><li>Dominant Species: </li></ul><ul><ul><li>Species in a community that have the highest abundance or highest biomass </li></ul></ul><ul><ul><li>Sugar maple in eastern North America </li></ul></ul><ul><li>Keystone Species: </li></ul><ul><ul><li>Important to a community because of their ecological roles (niches), not by numbers </li></ul></ul><ul><ul><li>Sea otters control sea urchin population, which controls kelp population </li></ul></ul>
  18. 19. Ecological Succession <ul><li>Ecological succession is a change in the species that live in a given area over a period of time </li></ul><ul><ul><li>One community replaces another </li></ul></ul><ul><li>Primary succession = occurs in places where soil is not yet formed </li></ul><ul><li>Secondary succession = occurs in places where there is soil, but where some disturbance has eliminated the previous community </li></ul>
  19. 20. Ecological Succession
  20. 21. Ecological Succession <ul><li>The first organisms to inhabit an area undergoing succession are known as pioneer organisms </li></ul><ul><ul><li>These are usually small organisms (bacteria, lichens, algae, etc.) </li></ul></ul><ul><li>The ecosystem goes through a number of stages, with each new stage usually consisting of larger organisms than the last one </li></ul><ul><li>Once a community has become stable and is not changing much, it is known as a climax community </li></ul>
  21. 22. Causes of Ecological Succession <ul><li>There are 3 major causes of ecological succession: </li></ul><ul><ul><li>Human Activities </li></ul></ul><ul><ul><li>- logging, mining, development, etc. </li></ul></ul><ul><ul><li>Natural Disasters/Disturbances </li></ul></ul><ul><ul><li>- fires, volcanic eruptions, etc. </li></ul></ul><ul><ul><li>3 . Natural Competition Among Species </li></ul></ul><ul><ul><li>- Fictitious example: </li></ul></ul><ul><ul><li>- turtles and frogs both eat crickets </li></ul></ul><ul><ul><li>- frogs are faster, turtles are slower </li></ul></ul><ul><ul><li>- frogs eat more crickets, turtles starve </li></ul></ul><ul><ul><li>- turtle population dies out, frog population </li></ul></ul><ul><ul><li> gets bigger </li></ul></ul>