CELL REPLACEMENT:In some parts of body example skin and digestive tract, cells are constantly sloughed off and replaced by new ones. New cells are formed by mitosis and so are exact copies of the cells being replaced. Similarly, red blood cells have short life span (about 4 months)and new red blood cells are formed by mitosis.
Regeneration:Some organism can regenerate parts of their bodies. The production of new cells is achieved by mitosis. For example; sea star regenerates its lost arm through mitosis.
Regeneration in sea star
Source of Photo
All data collected from my book of Science.