9-12

B1: Illustrate the cycles of matter in the environment and explain their interrelationships.

Curriculum Organizing Questions	What are some of the possible paths that molecules might take through the biosphere? How might it be possible to breathe in an atom that was once part of a dinosaur? If the earth suddenly had no living organisms on it, how would you expect it to change? In what ways do plants and animals affect the atmosphere? Why don't we run out of materials for life here on earth?
Elaboration	This LR involves an understanding of the processes that shape the earth, as well as the flow of matter through the global food webs. It is not necessary for students to have all of the details of how elements cycle (e.g., nitrogen fixation), but must understand the idea of conservation of matter on a global scale and the basic details of the water, carbon, nitrogen, and oxygen cycles in the biosphere.
Specific Ideas	Atoms and molecules on the earth cycle among the living and nonliving components of the biosphere. NSES C4a Chemical elements that make up the molecules of all living things pass through food webs and are combined and recombined in different ways.Benchmarks 5E3 Living organisms play roles in the cycling of carbon, oxygen, nitrogen, and water on the earth. NSES C4d Matter is transformed but is conserved. NSES C5f At times, environmental conditions are such that plants and marine organisms grow faster than decomposers can recycle them back to the environment. Layers of energy-rich orgainic material have been gradually turned into great coal beds and oil pools by the pressure of the overlying earth.Benchmarks 5E1
Developmental & Instructional Implications	There seems to be an intuitive disbelief of increase in mass from incorporation of gaseous matter. Many students will state that carbon dioxide is absorbed, but do not understand that it is provides much of the mass of a tree, for example. Students seem not to realize that the body materials of organisms is the food of the next tropic level. The lack of the concept of conservation of matter underlies many of the conceptual problems in this area.Benchmarks Research p. 337 Students generally seem unaware of the importance of microbes as recyclers of carbon, nitrogen, water and minerals. Many students may also have trouble believing that producers exist in aquatic ecosystems. Some pupils see no connection between the oxygen / carbon dioxide cycle and other processes involving the production, consumption and use of food. Even at age sixteen few pupils have a view of matter that involves conservation in a variety of contexts such as photosynthesis, assimilation of food, decay and respiration. Driver p. 57
Examples

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