Geoffrey West is a professor and past president of the Santa Fe Institute. He is a high energy physicist turned quantitative biologist who works on complex networks. In this very interesting conversation (see link below), which is a part of Cambridge Nights Series, he talks about amazingly simple scaling behavior seen in all species, including trees, which gives predictive power to the biological systems. For example, for a given mass of the species one can predict how long it is going to live, based on scaling behavior of metabolic rates with mass. I was always interested in learning more about the quantitative nature of the biological mechanisms, because there is a generic underlying physical phenomena at work for any biological system, and there must be a way to understand and predict the evolution of these systems based on these phenomena.