This book is the study of all codes of life with the standard methods of science. The genetic code and the codes of culture have been known for a long time and represent the historical foundation of this book. What is really new in this field is the study of all codes that came after the genetic code and before the codes of culture. The existence of these organic codes, however, is not only a major experimental fact. It is one of those facts that have extraordinary theoretical implications. The first is that most events of macroevolution were associated with the origin of new organic codes, and this gives us a completely new reconstruction of the history of life. The second implication is that codes involve meaning and we need therefore to introduce in biology not only the concept of information but also the concept of biological meaning. The third theoretical implication comes from the fact that the organic codes have been highly conserved in evolution, which means that they are the greatest invariants of life. The study of the organic codes, in short, is bringing to light new mechanisms that have operated in the history of life and new fundamental concepts in biology.

The genetic code appeared on Earth with the first cells. The codes of cultural evolution arrived almost four billion years later. These are the only codes that are recognized by modern biology. In this book, however, Marcello Barbieri explains that there are many more organic codes in nature, and their appearance not only took place throughout the history of life but marked the major steps of that history. A code establishes a correspondence between two independent 'worlds', and the codemaker is a third party between those 'worlds'. Therefore the cell can be thought of as a trinity of genotype, phenotype and ribotype. The ancestral ribotypes were the agents which gave rise to the first cells. The book goes on to explain how organic codes and organic memories can be used to shed new light on the problems encountered in cell signalling, epigenesis, embryonic development, and the evolution of language.

Early Thoughts on RNA and the Origin of Life The full impact of the essential role of the nucleic acids in biological systems was forcefully demonstrated by the research community in the 1950s. Although Avery and his collaborators had identified DNA as the genetic material responsible for the transformation of bacteria in 1944, it was not until the early 1950s that the Hershey-Chase experiments provided a more direct demonstration of this role. Finally, the structural DNA double helix proposed by Watson and Crick in 1953 clearly created a structural frame work for the role of DNA as both information carrier and as a molecule that could undergo the necessary replication needed for daughter cells. Research continued by Kornberg and his colleagues in the mid-1950s emphasized the biochemistry and enzymology of DNA replication. At the same time, there was a growing interest in the role of RNA. The 1956 dis covery by David Davies and myself showed that polyadenylic acid and polyuridylic acid could form a double-helical RNA molecule but that it differed somewhat from DN A A large number of experiments were subsequendy carried out with synthetic polyribonucleotides which illustrated that RNA could form even more complicated helical structures in which the specificity of hydrogen bonding was the key element in determining the molecular conformation. Finally, in I960,1 could show that it was possible to make a hybrid helix.

"Yet another cell and molecular biology book? At the very least, you would think that if I was going to write a textbook, I should write one in an area that really needs one instead of a subject that already has multiple excellent and definitive books. So, why write this book, then? First, it's a course that I have enjoyed teaching for many years, so I am very familiar with what a student really needs to take away from this class within the time constraints of a semester. Second, because it is a course that many students take, there is a greater opportunity to make an impact on more students' pocketbooks than if I were to start off writing a book for a highly specialized upper- level course. And finally, it was fun to research and write, and can be revised easily for inclusion as part of our next textbook, High School Biology."--Open Textbook Library.

Biology for AP® courses covers the scope and sequence requirements of a typical two-semester Advanced Placement® biology course. The text provides comprehensive coverage of foundational research and core biology concepts through an evolutionary lens. Biology for AP® Courses was designed to meet and exceed the requirements of the College Board’s AP® Biology framework while allowing significant flexibility for instructors. Each section of the book includes an introduction based on the AP® curriculum and includes rich features that engage students in scientific practice and AP® test preparation; it also highlights careers and research opportunities in biological sciences.