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Elementary Science Education

Nature’s Great Cycles

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      Bernard Nebel

      Seeing plants, animals, fungi and bacteria as an interacting network of organisms, we can discern nature’s great cycles. All the chemical elements required by living organisms are continually recycled from the environment through plants, animals, fungi or bacteria, back to the environment to be recycled again. A paramount  example is the  carbon cycle. Type carbon cycle images into your browser, and trace the pathway of carbon atoms around the cycle with your kids. Key points are:

      1. In the process of photosynthesis, plants take carbon atoms from carbon dioxide in the air and use them in building their roots, stems, leaves, flowers and fruits.
      2. Down the food chain from the plant itself to the bacteria feeding on the last remnant, carbon-containing molecules will be broken down for energy by the feeding organism (respiration).
      3. In the process of respiration, the carbon atoms are released back to the air as carbon dioxide to repeat the cycle again.

      A profound thought to ponder is that every carbon atom in our bodies, through the course of history,  has necessarily been recycled countless times and through every kind of organism on earth and will continue to be recycled into the future. In this manner, we do share life with every other living creature. Please share your thoughts or questions.

      Examine and contrast other nutrient cycles as you may wish. Carbon, which has a portion of its cycle in the air, is recycled by nature without problem. Mineral elements such as phosphorus, which come from the soil present more of a problem. In natural ecosystems, where plants, animals, fungi and bacteria are all living together in the same system, wastes carrying phosphorus are deposited within the system and recycled without problem. In our human system, wastes containing the phosphorus end up being deposited far from where the plants drew phosphorus from the soil. This requires both renurishing soils with phosphorus (fertilizer) and leads to over enrichment of locations where wastes are finally discharged. Again: questions, thoughts?




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