Developmental Biology 12th Edition
With biology going into smaller and smaller realms, it is sometimes good to contemplate the grand scheme of things rather than the details, to “seat thyself sultanically among the moons of Saturn” (in Herman Melville’s phrase). It is good, for instance, to get a perspective of developmental biology from outside the discipline rather than from inside it.
Remembering the Field’s Interdisciplinary Foundations
Developmental biology, history tells us, is an interdisciplinary field that is at the foundations of biology. Indeed, before the word biology came to be used, the living world was characterized as that part of the world that was developing. The organizers of the first meeting (in 1939) of the Growth Society, which was the precursor of the Society for Developmental Biology, claimed that development must be studied by combining the insights of
numerous disciplines, including genetics, endocrinology, biochemistry, physiology, embryology, cytology, biophysics, mathematics, and even philosophy. Developmental biology was to be more than embryology. It also included stem cells, which were known to generate the adult blood, and regeneration, which was seen to be
the re-activation of developmental processes and which was critical for healing in vertebrates and for reproduction of hydra, flatworms, and numerous other invertebrates. The first articles published in the journal
Developmental Biology showcased embryology, regeneration, and stem cells, and the different ways of studying them.
Throughout this new 12th edition you will see a return to some of these founding ideas of interdisciplinary
developmental biology, namely regeneration, morphomechanics, plants, and the genetic control of development.
Indeed, regeneration has historically been a major part of developmental biology, for it is a developmental phenomenon that can be readily studied. Experimental biology was born in the efforts of eighteenth-century naturalists to document regeneration and to examine how it was possible. The regeneration experiments of Tremblay (hydras), Réaumur (crustaceans), and Spallanzani (salamanders) set the standard for experimental biology and for the intelligent discussion of one’s data.
More than two centuries later, we are beginning to find answers to the great problems of both embryology and regeneration. Indeed, the conclusions of one support the research of the other. We may soon be able to alter the human body so as to permit our own limbs, nerves, and organs to regenerate. Severed limbs could be restored, diseased organs could be removed and regrown, and nerve cells altered by age, disease, or trauma could once again function normally. The ethical issues this would exacerbate are only beginning to be appreciated. But if we are to have such abilities, we first have to understand how regeneration occurs in those species that have this ability. Our new knowledge of the roles that paracrine factors and physical factors play in embryonic organ formation, plus recent studies of stem cells and their niches, has propelled what Susan Bryant has called “a regeneration renaissance.” Since “renaissance” literally means “rebirth,” and since regeneration can be seen as a return to the embryonic state, the term is apt in many ways.
Notice that biophysics was also an early part of the mix of developmental biology. This area, too, is having a renaissance. The physical connections between cells, the strength of their bonding, and the tensile strength of the material substrates of the cells are all seen to be critical for normal development. Physical forces are necessary for sperm-egg binding, gastrulation, heart development, gut development, the branching of the kidney and lung epithelia, and even the development of tumors. Physical forces can direct the development of stem cells toward particular fates, and they can determine which part of the body is left and which is right. The patella of our kneecap doesn’t form until we put pressure on it by walking. In many cases, physical forces can direct gene expression. Lev Beloussov, a pioneer in this area, has called this the “morphomechanics of development.”
Another area that was prominently represented in the early programs of developmental biology was plant development. Plant development had much in common with regeneration, as “adult” plants could redevelop entire parts of their bodies. Whereas in animal biology the study of development diverged from the study of physiology, that separation was not evident in plant biology. Moreover, while many animals quickly set aside a germline that was to become the sperm or eggs, this was not the case in plants. Such comparisons between plants and animals are now present throughout this text, and they serve to highlight the fundamental developmental processes that are present across phyla and even kingdoms of life.
But the genes remain the center of focus in developmental biology. And the more we learn about them, the more interesting and complex these genes become. New advances in “single cell transcriptomics” have given us an amazing privilege—the ability to look at the gene expression patterns of individual cells as they develop. An individual’s cells may all have the same genes, but their different positions in the embryo cause different genes to be active in each cell. It’s a symphony of relationships, each cell providing the context for another. If development is the performance, then the genome is the script or score. As anyone who has gone to concerts knows, different bands perform the same score differently, and the same band will play the same song differently on two successive nights. Environment is also critical—hence, the new interest in plasticity and symbiosis in development.
Developmental biology has also taken on a new role in science. More than any other biological science, it demonstrates the critical importance of processes as opposed to entities. In many organisms, the same process can be done by different molecules. “It’s the song, not the singer,” say Doolittle and Booth, and we can be thankful that there are redundant pathways in development—if one pathway fails, another is often able to take over its function. The entity/process split in developmental biology mirrors the particle/wave dichotomy in physics. It is a “both, and” situation, rather than an “either/or” situation. In 1908, the Scottish physiologist J. S. Haldane said, “That a meeting point between biology and physical science may at some time be found, there is no doubting. But we may confidently predict that if that meeting-point is found, and one of the two sciences is swallowed up, that one will not be biology.” Developmental biology may well solve the longstanding mysteries of physics.
New to the Twelfth Edition
In this current volume, we have attempted to track this amazing fulfillment of the early promises of developmental biology. To this end, the book has undergone its own morphogenesis.
Plant development covered throughout
We have now incorporated plant material into the relevant chapters. Instead of segregating plant developmental
biology into a single (and often unassigned) chapter, we have integrated essential plant biology into the chapters on cell specification, gene regulation, cell communication, gamete production, fertilization, axis determination, organ formation, and regeneration.
Upgraded and expanded chapter on regeneration
We have also expanded the chapter on regeneration, which we are proud to say offers a unique summary of the field. It both captures the fascinating problems of post-embryonic development that regeneration seems to solve and provides a logical framework for the known mechanisms of regeneration, based on an organism’s degree of regenerative capacity. We feel that this chapter will be an excellent place for anyone interested in this area to start.
Updates throughout all chapters
All of the chapters have received important updates, from the introductory chapter’s broader evolutionary perspective to new material on the morphomechanics of development during Drosophila gastrulation and the formation of mammalian lungs. Special consideration was also given to the increasing use of whole-genome, transcriptomic approaches, which are dramatically shaping our understanding of cell differentiation.
A new, student-centered approach
From a pedagogical standpoint, it is also good to get an outside perspective of how students are learning developmental biology—the perspective of the student experience. For decades, it has been the responsibility of textbooks like ours to be the most comprehensive sources for the field’s foundational content. Although this responsibility still remains, the reality is that students are inundated with an overwhelming myriad of sources vying for their attention. If there was ever a time a student of developmental biology needed a guidebook to navigate through this dense and diverse ecosystem of texts, online resources, and infinitely expanding scientific literature, the time is now and the guidebook this new volume of Developmental Biology.
• Focused and streamlined coverage. Over the years, as new knowledge has grown, so has our own textbook, which was reaching a size that might itself trigger student overload and defeat the purposes of engagement and deep learning. The information bombarding students is not going away; therefore, they need not only access to the information but also a clear guide that fosters movement from the essential ideas to the complex mechanisms and finally to inclusive invitations that welcome their research in this field. We have both reduced and reorganized the content in each chapter to achieve a clear and supportive lattice so that both the professor and the student can more easily navigate the increasing volume and complexity of developmental biology.
• Innovative pedagogy: Empowering students to craft their own learning. The first material students will encounter in each section of a chapter represents the most essential content. We have introduced a new element called “Further Development,” which highlights content we feel represents some of the more complex ideas in the field. In addition, students will also come across invitations to view some Further Developments online. These online topics represent fantastic opportunities for students to further develop their understanding of developmental biology along paths of their own interest—paths of investigation that professors can have confidence match the standards of quality seen throughout the textbook (unlike some other online sources). The special in-text features of previous editions—Dev Tutorials, Developing Questions, Next Step Investigations, and citations throughout—are still in place to play important roles in empowering students to take that final leap to engage with the developmental biology literature. To better support students’ use of the research literature, we now include a new Appendix focused on how to find and analyze research articles in developmental biology.
Thanks to this new organization of content, professors and students will now be in complete control of what level of material may be most appropriate. We are proud to introduce Developmental Biology 12e, as it still provides direct access to all levels of the content but without diluting its quality and the overall learning experience.
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|March 19, 2022|