1717 snakehead fish eats everything and has no known

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Unformatted text preview: akehead fish eats everything and has no known predators Can grow 1 ½ meters long, introduced in Maryland and working its way south Introduced by foreigners, released open 11/30/07 Food Webs – movement of energy from one area of community to another area of community Figure 17.4 Summarize feeding relationships in ecosystem or community Naturally occurring food webs are highly complex Trophic dynamics- transfer of energy from one part of the ecosystem to another o Top trophic level= apex predator (ex: owl) Eastern Deciduous Forest (where we are now)—community portrait MANY COMPLEX AND INTERACTING FACTORS within food webs Energy made available by plants/producers Bottom is what makes everything possible! (plants!) Plants, trees, organic matter, acorns fruits Bees, mosquitos, flys, squirrels, beetles, butterflies Spiders, salamander, mouse Apex predator=owl (carnivore) When all these die, they become organic matter which is food for microbes Food Chain Trophic levels – position in food web determined by the number of transfers of energy in that level Producers (trees, herbs, etc.) - Autotrophs Primary Consumers (mice, moths, etc.) – Herbivores, Heterotrophs Secondary Consumers (birds, spiders, etc.) – Carnivores, Heterotrophs Tertiary Consumers (owl) – Carnivores, Heterotrophs Decomposers - Heterotrophs Eastern Deciduous Forest Fig. 18.17 Forest Energy Budget Energy enters into ecosystem via primary producers and make it available to everything else Water shed #6, measured photosynthetic photon flux density beaming down on forest and converted sunlight to calories was 480,000kcal/m2 (100% solar radiation) 1st law of thermodynamics- energy cannot be created or destroyed 2nd law of thermodynamics - No transformation of energy is 100% efficient; and the amount of usable energy decreases ******SOME IS ALWAYS LOST TO THE SURROUNDINGS AS HEAT 15% reflected, 41% heat, 42% evapotranspiration—so only 2.2% goes into plant production (fixed) Primary producers take in inefficient energy from photosynthetic photon flux active radiation, only 1% at net primary production available to heterotrophs Most energy stored as DEAD organic matter (upper portion of soil surface and where you have leaf litter)—largest single pool of energy 1 kilocalorie per meter square Energy flow through ecosystems The majority of organic matter is found in the top 36cm of soil 2nd major in the biomass Energy losses limit number of trophic levels in ecosystems (rarely more than 3 levels above autotriphs) Assumptions: 50% of energy used for a heat tax for respiration 10% of energy passed on to next trophic level - THE TEN PERCENT RULE 40% incorporated as biomass which eventually goes to decomposers More on the ten percent rule: Because of this inefficiency there are seldom more than three trophic levels above autotrophs An ecosystem will always try to maximize its energy storage Energy loss always limits the number of trophic levels in an ecosystem Energy loss can be reduced or delayed due to storage The more complex the ecosystem is, the longer energy is stored Assimilation Efficiency = Energy assimilated / Energy ingested X 100% Assimilation - incorporation of any materials into tissues, cells, and fluids of an organism Ray Lindeman: Lake Mendota Ingestion Assimilation Assimilation Efficiency PP 1,188,720 4,800 0.4% PC 520 420 81% SC...
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