The sun is a major source of energy for changes on the Earth's surface. The sun's energy arrives as light with a range of wavelengths, consisting mainly of visible light with significant amounts of infrared and ultraviolet radiation. NSES Content Standard Life Science 6-8 NSES Content Topic Living Systems Living systems at all levels of organization demonstrate complementarity of structure and function. Important levels of organization for structure and function include cells, organs, organ systems, whole organisms, and ecosystems. All organisms are composed of cells, the fundamental unit of life.
Cells carry on the many functions needed to sustain life.
They grow and divide, thereby producing more cells. This requires that they take in nutrients, which they use to power the work that cells do and to make the materials that a cell or an organism needs. Specialized cells perform specialized functions in multicellular organisms. Groups of specialized cells cooperate to form a tissue, such as a muscle. Different tissues are in turn grouped together to form larger functional units, called organs.