A cell is the smallest unit to be alive a tissue is a group of similar cells together. An organ is a group of two or more tissue. An organ system is a group of organs.
Most complex organisms consist of various organ systems that are dependent on other organ systems. These organ systems are made up of multiple organs that work together to perform a specific function, organs are made up of tissues, and tissues are made up of cells that work collectively.
Several body systems work together to accomplish a task. For example, the respiratory and circulatory systems work together to bring oxygen to the body and remove carbon dioxide from the body. The lungs provide a place where oxygen enters the blood and carbon dioxide is removed from the blood. The body contains organs and organ systems that interact to perform all the functions necessary for the survival and growth of an organism.
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