What is Life? The question has been asked before, famously by Nobel Prize-winning physicist Erwin Schrödinger in 1944. Now biologist Paul Nurse has addressed the question in his book, What is Life? He describes the wonder of the cell, where thousands of chemical reactions take place at a microscopic scale, all coordinated by the instructions contained in DNA. So what are essential qualities of life? It is an ability to change. A living thing is an entity that is subject to natural selection and can evolve. It needs a gene or a genome of genes and changes and adapts to the environment. The purpose is to survive and reproduce.