Organization Levels

"Unicellular organisms can function independently, but the cells of multicellular organisms are dependent upon each other and are organized into five different levels in order to coordinate their specific functions and carry out all of life’s biological processes. Cells are the basic structural and functional unit of all life, and examples include red blood cells and nerve cells. Tissues are groups of cells that share a common structure and function and work together. The four basic types of human tissues are connective, epithelial, muscle, and nerve tissue. Organs are groups of tissues arranged in a specific manner to support a common physiological function, such as the brain, liver, and heart. Organ systems are two or more organs that support a specific physiological function, such as the digestive system and central nervous system. An organism is the complete living system capable of conducting all of life’s biological processes."