Bits

We open the final chapter with an illustration of the growth seen in several types of biological data over the past decades. This rapid growth in datasets prompts the need for the approaches of this book. We next play a game that invites us to encode DNA bases as yes or no questions. These yes or no questions form a natural measure of the information content of a message, as noted by Shannon. We explore the close link between Shannon entropy and traditional thermodynamic entropy. We then apply Shannon entropy (or diversity) to the problem of describing the species diversity of a microbial ecosystem. Next we remind ourselves that the information carried in the genome of every living thing is energetically costly to maintain, and yet we find that life has learned to store information far more efficiently than we do as humans. We close with a look at the central unsolved problem in biology: developing the models to explain how the information in each genome drives phenotypes, ecosystems, and eventually even the evolutionary paths taken by species.