12-3-09 - Biology 330 Class Notes 12/3/09 TROPHIC DIAGRMS:...

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Biology 330 – Class Notes – 12/3/09 TROPHIC DIAGRMS: IDEA : It’s hard to locate an organism on the trophic pyramid because they sort of belong in both categories, or in the category of omnivore based on the contents of their stomachs Peters suggests that the trophic concept of pigeonholing organisms into trophic pyramids and categories is LIMITING Graph: Trophic guilds - what do the fish eat, what's in their diet – QUESTION: is this correct? Bulk of the column – the fish are eating BOTH plant and animal material Less than 20% of the species in this food web are strict carnivores, but the other 80% are omnivorous – they eat both plant and meat material This is a problem! Where to place the fish? In the mineral resource flow chart , we knew exactly where the minerals were at each point in the diagram – tracking is more precise Could we come up with a similar diagram by coming up with a diagram that shows exactly what an organism eats and who eats that organism? Figure 3. Food web. Feeding relationships are shown by linkages between organisms. We know that the group of flies in the sense that the fly eats dead detritus material and diatoms This is a schematic diagram that shows you that the energy is woodland shedding trees – energy given off and/or We can see every organism’s position It shows you exactly what is being eaten It doesn’t matter if you classify an organism as herbivore, carnivore, or omnivore because we know exactly who is eating who Any pathway that links on organism at the bottom to the top there ARE MANY COMBINATIONS/POSSIBILITIES – every combination that links the organisms together is a food chain We’re moving from bottom to top flow of who eats who Figure 4. Diagram summarizing open-water trophic interrelationships in Lake George, Uganda
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Pelagic Food Web of Lake Okeechobee This is a very complete food web The numbers represent the number of species 12 Y – 12 species of Young fish SAV – submerged aquatic vegetation DETR – detritus The loop represents the fact that some fish eat each other – cannibalism IDEA : If we had a bunch of food chains and looked for patterns, what could we tell about energy flow? Resource use in Lake Okeechobee, Florida. Number of consumers exploiting different resources in pelagic and littoral food webs. 1. Use of resources a. Resource use – pelagic (open water) i. Detritus – 30 or so vertebrates eating detritus and 150 invertebrates eating detritus b. Resource use – littoral (near-shore area that includes substrate and sediments) i. Detritus – used by more taxa than any other food source Table 1. Results from recent studies, regarding the relative importance of detritiovres and omnivores in aquatic terrestrial food webs.
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12-3-09 - Biology 330 Class Notes 12/3/09 TROPHIC DIAGRMS:...

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