Key Idea 6:  Plants and animals depend on each other and their physical environment.
6.1  Describe the flow of energy and matter through food chains and food webs.
Major Understandings	Suggested Activity
6.1a  Energy flows through ecosystems in one direction, usually from the Sun through producers to consumers and then to decomposers.  This process may be visualized with food chains or energy pyramids.
6.1b  Food webs identify feeding relationships among producers, consumers, and decomposers in an ecosystem
6.1c  Matter is transferred from one organism to another, and between organisms and their physical environment.  Water, nitrogen, carbon dioxide, and oxygen are examples of substances cycled between the living and nonliving environment.
6.2  Provide evidence that green plants make food and explain the significance of this process to other organisms.
Major Understandings	Suggested Activity
6.2a  Photosynthesis is carried on by green plants and other organisms containing chlorophyll.  In this process, the Sun's energy is converted into and stored as chemical energy in the form of a sugar.  The quantity of sugar molecules increases in green plants during photosynthesis in the presence of sunlight.
6.2b  The major source of atmospheric oxygen is photosynthesis.  Carbon dioxide is removed from the atmosphere and oxygen is released during photosynthesis.
6.2c  Green plants are the producers of food which is used directly or indirectly by consumers.