Benchmark 6C
The Human Organism: Basic Functions
Grades 6-8, page 137

Organs and organ systems are composed of cells and help to provide all cells with basic needs.

NSES Content Standard C 
Life Science: Structure and function in living systems
Grades 5-8, page 156
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. Each type of cell, tissue, and organ has a distinct structure and set of functions that serve the organism as a whole.