organelle- a human cell typically consists of flexible membranes that enclose cytoplasm, a water-based cellular fluid together with a variety of tiny functioning units cells- the smallest independently functioning unit of a living organism tissues- a group of many similar cells that work together to perform a specific function organs- distinct structure of the body composed of two or more tissue types organ system- a group of organs that work together to perform major functions or meet physiological needs of the body organisms-level is the highest level of organization.a living being that has a cellular structure