18_FoodWebs_2 - 1 Marine Food Webs II Outline Friday 1....

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Unformatted text preview: 1 Marine Food Webs II Outline Friday 1. Some definitions 2. Zooplankton Groups 3. Simplifying Food Web Conceptualizations 4. Blue Planet DVD Wednesday 1. Size-Structured Food Webs 2. Trophic Pyramid 3. Trophic Transfer Efficiency a) exploitation efficiency b) gross production efficiency 4. Consequences of food chain length on harvestable fish production Trophic Structure of Marine Food Webs 2 Autotrophs : Group of organisms whose carbon for growth comes from non-organic sources . For example, phytoplankton are autotrophs because they use CO 2 for their carbon needs. Heterotrophs : Group of organisms whose carbon for growth comes from pre-formed organic carbon material . For example, herbivorous zooplankton are heterotrophs because they consume phytoplankton for their carbon needs. Carnivores would also be heterotrophs Classifying Organisms into Broad Categories Based on Feeding Mode Trophic Level- nutritional level within a food chain or food web e.g., primary producer (i.e., autotroph), primary consumer (herbivore), secondary consumer (first carnivore), tertiary consumer (second carnivore), etc A more refined grouping Broadest possible grouping Food Chains and Food Webs Food Chain- depiction of material and/or energy flow in an ecosystem using a simple linear sequence of connections between trophic levels Food Web- depiction of material and/or energy flow in an ecosystem using a web of connections between trophic levels 3 1. how is a particular species population assigned to a given trophic level? 2. What determines the efficiency of transfer of carbon or energy from one trophic level to the next? 3. What are the consequences of trophic transfer efficiency on setting the upper limit of harvestable fish production? 4. What regions of the ocean are responsible for the greatest levels of harvestable fish and why? Questions to be Addressed About Marine Food Chains How do we assign an organism to particular trophic level? The first question to ask: Is the Organism Autotrophic or Heterotrophic ? The answer to this question is pretty straightforward because it amounts to asking Does the organism contain chlorophyll? yes , then it is an autotroph no , then it is a heterotroph 4 If the Organism is Heterotrophic, Then Ask: Is The Heterotrophic Organism a Primary Consumer or a Secondary Consumer or a Tertiary Consumer etc? This question has the potential of being difficult to answer because all heterotrophic organisms share the same trait of not having chlorophyll. To get to the answer, the following logic is used 1. Life in fluid suspension does not allow animals the opportunity to sit around and nibble on their prey over an extended period of time....
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This note was uploaded on 09/28/2008 for the course EAS 1540 taught by Professor Monger during the Fall '07 term at Cornell University (Engineering School).

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18_FoodWebs_2 - 1 Marine Food Webs II Outline Friday 1....

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