Final answer:
Stem cells are necessary for specialized cells that cannot divide again.
Step-by-step explanation:
Cells that renew constantly throughout life also have specialized cells that are unable to divide without stem cells. Stem cells are unspecialized cells that can divide without limit as needed and can differentiate into specialized cells. These stem cells play a crucial role in replacing terminally differentiated cells that cannot divide again, such as nerve cells, skeletal muscle fibers, and cardiac muscle cells. Stem cells ensure the continuous renewal of these specialized cells, allowing the organism to grow, develop, and maintain its health.