final_handout

final_handout - MIT Department of Biology 7.014...

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MIT Department of Biology 7.014 Introductory Biology, Spring 2005 The 7.014 Final Exam *YOU MUST BRING YOUR ID. This will be a cumulative, closed book exam. Please bring a non- programmable calculator.
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Question 1 Your ongoing interest in bioluminescent organisms has lead you to study the Hawaiian squid, Euprymna scolopes . Most nocturnal creatures cast shadows under the bright Hawaiian moonlight, and are easy prey to predatory fish. This type of squid can shine light downwards to match the moonlight and avoid casting a shadow thereby decreasing predation. To provide squid for your studies, you maintain a large, self-supporting squid tank. The food web of the tank is shown below. phytoplankton small fish squid detritivores When your tank is at steady state, you can harvest 10 kg of squid carbon/week and all the other biomasses (phytoplankton, fish, squid, and detritivores) remain constant. Given the following values: • NPP of phytoplankton = 2.0 kilograms of organic carbon per gram of phytoplankton per day • plant production efficiency = 60% • fish exploitation efficiency = 50% • fish assimilation efficiency = 20% • fish net production efficiency = 5% • squid exploitation efficiency = 50% • squid assimilation efficiency = 80% • squid net production efficiency = 40% a) What NPP (in kilograms of carbon) is required to support a harvest of 10 kg of squid carbon per week at steady state? Show your work. 2
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Question 1, continued b) Month after month, your squid harvest is 10 kg/week and all the biomasses remain constant. One month, you find that you can only harvest 5 kg of squid carbon/week and maintain steady state. You suspect that something has contaminated your tank and reduced your yield. You propose two models to account for the reduction in yield. To test these models, you measure the respiration rate of the detritivores in the tank. You find that detritivore respiration has increased by 5 kg of carbon per week. Model 1: Phytoplankton photosynthesis is inhibited so that they now only produce 1.0 kilogram of organic carbon per gram of phytoplankton per day, but at this new steady state, all other efficiencies remain constant. i) Is this model consistent with your measurement? Explain. Model 2: 5 kg of fish per week are dying with all other efficiencies remaining constant. ii) Is this model consistent with your measurement? Explain. c) In their native ocean environment, the squid feed on a wide variety of small fish and invertebrates. You suspect that the squid is the keystone species in this ecosystem. What experiment could you do to test this theory? What result do you predict? Question 2 a) You want to build a larger squid facility. To make better use of your resources, you plan to construct a life table to determine the mortality rate, fecundity, and the net replacement value of your population. You follow 1000 squid eggs and collect the data below.
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This note was uploaded on 11/11/2011 for the course BIO 7.012 taught by Professor Lander during the Fall '10 term at MIT.

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final_handout - MIT Department of Biology 7.014...

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