This process gets rid of unneeded cells and is particularly important for
“sculpting” tissue and organ structure during development of the embryo (or
larval metamorphosis in insects), but may occur at any time even in adult cells
when a tissue needs to be remodeled.
Signals to trigger apoptosis may come from within the cell or from outside, by
stimulating suicide receptors in the cell’s external membrane. Internal signals
producing apoptosis depend on interactions of several proteins and may serve to
protect the organism from cancer by killing cells that have pre-cancerous