Describe how an organism is made up of interacting body systems.

In multicellular organisms, the body is a system of multiple, interacting subsystems. Subsystems are groups of cells that work together to form tissues. Organs are groups of tissues that work together to perform a particular body function. Tissues and organs are specialized for particular body functions.

goog may have it for you

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.