34_communityecology2_forupload

34_communityecology2_forupload - Community Ecology Trophic...

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Unformatted text preview: Community Ecology Trophic Structure Trophic structure is the feeding relationships between organisms in a community It is a key factor in community dynamics Food chains link trophic levels from producers to top carnivores Quaternary consumers Tertiary consumers Carnivore Carnivore Carnivore Carnivore Secondary consumers Carnivore Carnivore Primary consumers Zooplankton Herbivore Primary producers Phytoplankton Plant A terrestrial food chain A marine food chain Food Webs A food web is a branching food chain with complex trophic interactions Fig. 54-12 Humans Smaller toothed whales Baleen whales Sperm whales Elephant seals Leopard seals Crab-eater seals Birds Fishes Squids Carnivorous plankton Copepods Euphausids (krill) Phyto- plankton Species may play a role at more than one trophic level Food webs can be simplified by isolating a portion of a community that interacts very little with the rest of the community Food Webs Fig. 54-13 Sea nettle Fish larvae Juvenile striped bass Fish eggs Zooplankton Why are food webs typically fairly short? Why not 100,000 links? no. of species no. of trophic links no. of species productivity high medium low Data from tree holes with food webs containing microbes, mosquito larvae that eat microbes, and predators that eat the mosquito larvae Food Webs Limits on Food Chain Length Each food chain in a food web is usually only a few links long Two hypotheses attempt to explain food chain length: the energetic hypothesis and the dynamic stability hypothesis The energetic hypothesis suggests that length is limited by inefficient energy transfer The dynamic stability hypothesis proposes that long food chains are less stable than short ones Most data support the energetic hypothesis Limits on Food Chain Length Fig. 54-14Fig....
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34_communityecology2_forupload - Community Ecology Trophic...

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