* Tissue: A group of similar cells that work together to perform a specific function. Examples include muscle tissue, nervous tissue, and epithelial tissue.
* Organ: A structure made up of different tissues that work together to perform a complex function. Examples include the heart, lungs, and stomach.
* Organ System: A group of organs that work together to carry out major bodily functions. Examples include the digestive system, the respiratory system, and the circulatory system.
* Organism: A complete living being made up of multiple organ systems that work together to maintain life. Examples include a human, a dog, or a tree.
You can think of these levels as building blocks, with each level adding complexity and functionality to the next.
