One can think of death as just another fate that a cell can take on during development. In fact, lineally homologous cells often undergo cell deaths together, just as lineally homologous cells often have similar differentiation patterns. In C. elegans , cell death is not crucial for the survival of the organism, but it is in more complex animals. It also occurs in plants. These are all examples of apoptotic cell death, or cell suicide.
Apoptotic death is different from necrotic death in several ways.
Necrotic death of a cell is a response to damage or toxins in the environment. Cells dying a necrotic death due to lack of oxygen, for example, swell and burst, often causing further damage to surrounding cells. Apoptotic cells, on the other hand, do not burst, but rather exhibit shrinking, chromatin condensation, and blebbing. Apoptotic cells are also rapidly disposed of, engulfed and broken down by neighboring cells. Because of these characteristic features, it was proposed that there might be an actual program of cell death that is activated within a cell.