What is the functional center of a cell that governs activity and heredity called?

The functional center of a cell that governs activity and heredity is known as the nucleus. The nucleus serves as the control center, housing the cell's genetic material (DNA) and coordinating activities such as growth, metabolism, and reproduction. It plays a critical role in gene expression and regulation, influencing both the physiological functions of the cell and the transmission of hereditary information to subsequent generations.

In contrast, the other options have distinct functions within the cell. The cytoplasm is the gel-like substance that fills the cell and houses organelles, but it does not govern genetic information or cellular activities. Mitochondria are responsible for producing energy through cellular respiration, playing a key role in energy metabolism but lacking authority over cellular operations or genetic material. Ribosomes are the sites of protein synthesis, crucial for taking instructions from the mRNA, but they do not contain or manage the cell's genetic information or activities directly. Thus, the nucleus is uniquely positioned to encompass these essential governing functions for the cell.