What are three reasons otherwise healthy cells die via apoptosis

→ not fully developed cells are killed – in the embryonic brain cells that are not incorporated into the brain network are killed via apoptosis → there are more than needed – it takes energy to keep extra cells alive so excess cells die via apoptosis → they have outlived their usefulness – foetuses have webbed toes and fingers and when this feature is no longer needed the cells connecting these extremities die via apoptosis – also when you recover from an illness any leftover immune cells that are not needed anymore die via apoptosis