LabManual_EcoFlask - Manual for eco flask lab

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Foundations of Biological Sciences I Interactions within Ecosystems - 1 Interactions within Ecosystems Ecology is the branch of biology that describes relationships among organisms and interactions with their environment. Ecological studies often include both describing and counting the organisms in a given environment (of one specific population or of communities present in a given environment) as well as measuring rates of exchange of materials between organisms and their environment ( ecosystem interactions ). Living organisms are composed of selected groups of chemical elements, all of which are also found in the abiotic environment. These elements usually are combined in the form of more complex organic compounds within the body tissue of living organisms. For example, the protoplasm that comprises plant and animal cells is composed principally of large organic molecules, including carbohydrates, fats, proteins, and nucleic acids, which are composed of elements (carbon, hydrogen, nitrogen, oxygen,…). All of the elements and organic compounds needed for life are termed nutrients . Living organisms have a never- ending need for nutrients, but at the same time the earth’s supply of them is limited and constant. Nutrient cycles provide means whereby elements can move from the nonliving ( abiotic ) world through the living ( biotic ) world and back. Nutrient cycles are “driven” in large part by nutrient uptake (e.g., feeding) and nutrient release (e.g. urine and feces production, decomposition) by organisms in the ecosystem. Geological and chemical factors are also important. For this reason, they are called biochemical cycles . There are many such cycles, including the carbon cycle , the nitrogen cycle , the phosphorus cycle , and the oxygen cycle . In the oxygen cycle, plants first use CO 2 and H 2 O to produce sugar during photosynthesis . Oxygen is released to the environment as a by-product. Light provides the energy for this process. The oxygen in our atmosphere is ultimately the product of photosynthesis (past and present). Oxygen is then used by practically all organisms (including plants) for respiration , in which oxygen and sugars are used to produce energy (and the by-products CO 2 and H 2 O). Without oxygen, only a few organisms (e.g. yeast, some bacteria) would be able to survive. According to the primary mechanism they use to obtain essential nutrient, living organisms can be classified into two major categories: autotrophs and heterotrophs. Autotrophs can synthesize complex organic molecules from simple chemical elements obtained directly from the abiotic components of the environment. Most autotrophic organisms are photoautotroph. They have chlorophyll (or some other photosynthetic pigment) that allows them to capture the energy of the sun. All green plants , most algae , and some bacteria (including cyanobacteria , sometimes called “blue-green-algae”) are autotroph. Heterotrophs
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LabManual_EcoFlask - Manual for eco flask lab

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