Apoptosis involves multiple pathways coming together to say that a cell is no longer needed during development. Any one of the individual pathways is not enough to induce apoptosis: only together can they induce cellular suicide. This shows that apoptosis is emergent-- it only appears when many parts come together to create another, higher level of organization.
Work Step by Step
Review Ch. 1 for information about emergent properties, which is one of the main themes of this book. You will notice that many of the Synthesis/Evaluation level questions in this textbook involve such emergent properties.