Bio II Slide Set XVI

Bio II Slide Set XVI - III. Community ecology (contd.) E....

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Unformatted text preview: III. Community ecology (contd.) E. Complex community interactions 1. Trophic structure: food chains and webs 2. Effects of species interactions on species diversity a. dominant species and the rivet vs. redundant model of community structure b. Example: American chestnut c. Example: keystone predators i. Paines rocky intertidal experiment ii. PaciFc kelp bed community . Effects of disturbance on species diversity 1. Ecological succession (primary, secondary) Monday, June 13, 2011 Fig. 53.12 Community trophic structure : = hierarchial feeding relationships within a community food chain = the linear transfer of food energy through a community trophic level = the position of a species in a food chain based on its nutritional source autotroph- captures sun energy and transfers Monday, June 13, 2011 Fig. 53.13 An Antarctic marine food web: more than one food chain linked together Omnivore: a species that can feed at more than 1 trophic level (us!) ***Note direction of arrows! (= E Fow)*** Monday, June 13, 2011 These consume non-living/dead organic matter and help recycle organic & inorganic compounds back into the environment. bacteria, too fungi earthworms vultures are scavengers Food webs also include decomposers, scavengers & detrivores that feed at all levels of a food chain. Monday, June 13, 2011 Fig. 53.12 At the base of the food chain: Monday, June 13, 2011 Fig. 53.12 primary producers or autotrophs (self-feeders) who make their own organic food molecules (glucose) using solar energy, CO 2 + H 2 O (i.e., photosynthetic autotrophs ) At the base of the food chain: Monday, June 13, 2011 or by using energy obtained by oxidizing inorganic substances (i.e., chemo autotrophs) deep-sea hydrothermal vent community with chemosynthetic bacteria as primary producers in the local food web (they oxidize hydrogen sulFde from the vents) Monday, June 13, 2011 Bacteria grow into a thick mat which attracts other organisms such as amphipods and copepods which graze upon the bacteria directly. Larger organisims such as snails, shrimp, crabs, tube worms, fsh and octopi Form a Food chain oF predator and prey relationships. Monday, June 13, 2011 Not all primary production gets converted into plant biomass (plants use some E to live) & not all primary production gets transferred up a food chain (some E lost as heat) NOTE: so only ~10% of energy passed along each step of chain Why are there limits to food-chain length ? One explanation: The energetic hypothesis Monday, June 13, 2011 Energy is Lost at Each Trophic Level Fig. 54. 10 We can assess the trophic efFciency of a community by analyzing the percentage of production transferred from one trophic level to the next (e.g., ~10%) Trophic efFciency varies due to metabolic rate and diet ....
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Bio II Slide Set XVI - III. Community ecology (contd.) E....

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