Introduction / Rationale
If plants could not produce their own food, then there would be little life on this planet of ours. Plants are not only the basis of the food chain, but they also produce the oxygen we need to live and breathe. This unique ability comes from the miracle of photosynthesis and their capacity to store energy in chemical bonds that consumers eat to get the energy they need to survive. Energy is defined as the capacity to do work and all organisms need it to survive. The first law of thermodynamics states that energy can neither be created nor destroyed, only transformed from one form to another. Plants start this process by transforming the radiant energy of the sun into sugar. Consumers take advantage of this as their primary food source. After the consumer's life cycle is complete and the consumer is no longer alive decomposers come along and break the organisms down. This relationship returns the organism's remains back to the soil for the plants to start anew. Food chains are nature's way of transferring energy, allowing life to continue to grow, repeat, and the basis for this unit.
I teach in an urban, Title I elementary school where several of the children's parents are working more than one job and don't get to spend the time with their children that they would like. When they reach fifth grade, they are below grade level in multiple subjects and it takes a lot to get them to where they need to be. Our school uses departmentalized block periods, so 80 minutes per block allows me time to cover certain ideas in much detail. After getting to know my students, I find what their interests are and ways to better motivate them. An excellent hook is relating material to animals and the world around them.
With curriculum pacing in mind, I am always looking for ways to better integrate ideas within application. Science is a subject where boundless cause and effect relationships occur, and when observed and documented, lead to repetition and cycles. Because of this, there are many connections between interrelated ideas. This unit allows the concept of energy transfer to be modeled from its beginning to end. Life continues this planet because of the relationship between plants and animals. Plants need animals for carbon dioxide and animals need plants for food and oxygen. The driving force for this relationship is the energy of the sun, but the real miracle is that plants can make (or produce) their own food. Tremendous amounts of energy come from the sun, but only a small portion of it is used by plants for this process. Producers store energy in chemical bonds creating organic compounds that can last for a long, long time. Animals consume plants to get the energy they need to live. All of these organisms live, breed, and die. Then it's up to the decomposers to come along and recycle it all, putting the nutrients back in the ground and starting the process anew. It is this circle of life that sustains everything else and what we will investigate in this unit.
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