lab3 - Laboratory 3 Energy Flow: Photosynthesis and...

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Laboratory 3 Energy Flow: Photosynthesis and Respiration Objectives 1) To examine two components of energy flow and material cycling: photosynthesis and respiration. 2) To understand the factors that affect energy transformations in living organisms. 3) To improve skills in summarizing and graphically displaying data. A. Background 1) Energy Flow and material cycling All ecosystems, terrestrial or aquatic, large or small, exhibit certain fundamental properties, including: 1) Materials (such as water, gases, and nutrients) are cycled among trophic levels of the ecosystem. 2) Energy flows through the trophic levels of the ecosystem, driving the cycling of materials. Materials and energy behave very differently in an ecosystem, as well as in an individual organism. Unlike materials, energy can never be recycled, but it can be transformed from one type of energy to another (i.e. light energy can be converted to chemical energy). Energy transformation is never 100% efficient; some energy is always lost. In living systems, this "lost" energy is usually dissipated as heat . Due to the inefficiency of energy transfer between trophic levels, a continuous input of energy is required by the ecosystem. The ultimate source of that energy is, of course, the sun. The movements of energy and materials at the ecosystem level are the cumulative result of all of the individual transfers among the biotic components (i.e., the living organisms) and abiotic (non-living) components of that system. In this lab, rather than study the actual amounts of energy and material transferred at each step through an entire ecosystem, we will focus on the two fundamental biological processes that are central to exchanges among the living and non- living components. These two biological processes are photosynthesis and cellular respiration . Each of these is essential for both energy flow and material cycling, and each of them represent processes that occur at the level of the individual organism. During photosynthesis, green plants harvest light energy to synthesize complex organic materials (such as sugars) from simple inorganic molecules (such as CO 2 and H 2 O). The light energy from the sun is thus converted into the stored chemical energy represented by a sugar molecule. Living organisms can subsequently release this stored energy by the process of 18
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Sugars are broken down to yield energy, CO 2 , and H 2 O. Some of the energy obtained in this way is utilized for the maintenance, growth, and reproduction of all living things; some is lost as heat. Photosynthesis and respiration are the essential components of energy flow in an ecosystem, and they drive part of the cycling of carbon, oxygen and hydrogen. The products of photosynthesis fuel the reactions of respiration and the material by-products of respiration are the raw materials for photosynthesis; thus materials are recycled between the organisms within the ecosystem (Fig. 1). Figure 1.
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This note was uploaded on 04/21/2008 for the course BIO 110 taught by Professor Sikkel during the Fall '07 term at Centre College.

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lab3 - Laboratory 3 Energy Flow: Photosynthesis and...

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