Reviewers of THE NInth edition It is no longer possible(if it ever was) for one person to comprehend this entire field. As Bob Seger so aptly sings, " I've got so much more to think about., what to leave in, what to leave out. "The people who help me leave in and take out the right things are the reviewers. Their expertise in particular areas has become increasingly valuable to me. Their comments were made on early versions of each chapter, and they should not be held accountable for any errors that may appear Arkhat Abzhanov, Harvard university Kelly McLaughlin, Tufts University Radwan Abu-lssa, University of Michigan, Dearborn Sarah Millar, LIniversity of Pennsyloan William Anderson, Harvard university Kathleen Molyneaux, Case Western Reserve University Blanche Capel, Duke university Mary Mullins, University of pennsylvania Bradley Davidson, University of Arizona Barry Shur, Emory universiti Carol Erickson, University of California, Davis Ana Soto, Tufts University Susan Ernst, Tufts University Claudio Stern, University College London Mindy George-Weinstein, Lankenau Institute for David Stocum, Indiana University- Purdue University Medical research Stuart A. Kauffman santa fe institute Kathleen Sulik, University of North Carolina Daniel Kessler, University of pennsylvania Nicole Theodosiou Napier, Union College Laura Lee, Vanderbilt University ien Van Speybroeck, Ghent University Karen Liu, King's College London Steven Vokes, University of Texas Thomas Maynard, University of North Carolina Gary Wessel, Brown University David McClay, Duke University
Reviewers OF THE NINTH EDITION It is no longer possible (if it ever was) for one person to comprehend this entire field. As Bob Seger so aptly sings, "I've got so much more to think about... what to leave in, what to leave out." The people who help me leave in and take out the right things are the reviewers. Their expertise in particular areas has become increasingly valuable to me. Their comments were made on early versions of each chapter, and they should not be held accountable for any errors that may appear. Arkhat Abzhanov, Harvard University Radwan Abu-Issa, University of Michigan, Dearborn William Anderson, Haroard University Blanche Capel, Duke University Bradley Davidson, University of Arizona Carol Erickson, University of California, Davis Susan Ernst, Tufts University Mindy George-Weinstein, Lankenau Institute for Medical Research Stuart A. Kauffman, Santa Fe Institute Daniel Kessler, University of Pennsylvania Laura Lee, Vanderbilt University Karen Liu, King's College London Thomas Maynard, University of North Carolina David McClay, Duke University Kelly McLaughlin, Tufts University Sarah Millar, University of Pennsylvania Kathleen Molyneaux, Case Western Reserve University Mary Mullins, University of Pennsylvania Barry Shur, Emory University Ana Soto, Tufts University Claudio Stern, University College London David Stocum, Indiana University-Purdue University, Indianapolis Kathleen Sulik, University of North Carolina Nicole Theodosiou Napier, Union College Lien Van Speybroeck, Ghent University Steven Vokes, University of Texas Gary Wessel, Brown University
Media and Supplements to accompany Developmental Biology, Ninth Edition eBook(SBN978-0-87893-412-6) copy of the textbook. (See the inside front cover for details. DeuBio Laboratory: vade mecum is a rich multimedia learn- www.sinauer.com/ebooks ing tool that helps students understand the development New for the Ninth Edition, Developmental Biology is avail. of the organisms discussed in lecture and prepares them tble as an online interactive ebook at a substantial dis- count off the list price of the printed textbook. The inter- Differential Expressions series of videos, highlighting some ctive ebook features a variety of tools and resources that major concepts in developmental biology, famous experi make it flexible for instructors and effective for students. ments, and the scientists who performed them For instructors, the eBook offers an unprecedented oppor. Develop/ntal biology: tunity ze the of notes, Web links, images, documents, and more. Stu- A Guide for Experimental Study, Third Edition dents can readily bookmark pages, highlight text, add their MARY S. TYLER own notes, and customize display of the text. In addition, (Included in DevBio Laboratory: vade mec all of the in-text references to the Companion Website Web topics and to DeoBio Laboratory: uade mecum are integrat- This lab manual teaches the student to work as an inde ed into the ebook as direct links, so the student can easily pendent investigator on problems in development and pro- vides extensive background information and instructions Also available as a CourseSmart eBook (ISBN 978-0- for each experiment. It emphasizes the study of living of the printed book exactly, and includes convenient tools na for searching the text, highlighting, and notes. For more their work informationpleasevisitwww.coursesmart.com For the Instructor For the student available to qualified adopters) Companion Website Instructors Resource Library www.devbio.com The Developmental Biology, Ninth Edition Instructor's Resource Library includes a rich collection of visual Available free of charge, this website is intended to supple- resources for use in preparing lectures and other course ment and enrich courses in developmental biology. It pro- vides more information for advanced students as well as materials. The IRL includes: interviews, opinions, Web links, updates, and more. Refer ences to specific website topics are included throughout B A collection of videos illustrating key developmental each chapter as well as at the end of each chapter acess a Chick embryo cross-sections and chick embryo whe DevBio Laboratory: vade mecum mounts from DevBio Laboratory: vade mecum(Power- Point format) An Interactive Guide to Developmental Biology Video segments from Dev Bio Laboratory: vade mecum http://abs.devbio.com a Instructor's Reference Guide for Differential Expressions MARY S TYLER and RoNALD N. KoZlOWSKI New for Version 3, DevBio Laboratory: uade mecum is now online Access to the program is included with every new
Media and Supplements to accompany Developmental Biology, Ninth Edition eBook (ISBN 978-0-87893-412-6) www.sinauer.com/ebooks New for the Ninth Edition, Developmental Biology is available as an online interactive ebook, at a substantial discount off the list price of the printed textbook. The interactive ebook features a variety of tools and resources that make it flexible for instructors and effective for students. For instructors, the eBook offers an unprecedented opportunity to easily customize the textbook with the addition of notes, Web links, images, documents, and more. Students can readily bookmark pages, highlight text, add their own notes, and customize display of the text. In addition, all of the in-text references to the Companion Website Web topics and to DevBio Laboratory: vade mecum3 are integrated into the ebook as direct links, so the student can easily access a wealth of additional material as they read. Also available as a CourseSmart eBook (ISBN 978-0- 87893-409-6). The CourseSmart eBook reproduces the look of the printed book exactly, and includes convenient tools for searching the text, highlighting, and notes. For more information, please visit www.coursesmart.com. For the Student Companion Website www.devbio.com Available free of charge, this website is intended to supplement and enrich courses in developmental biology. It provides more information for advanced students as well as historical., philosophical, and ethical perspectives on issues in developmental biology. Included are articles, movies, interviews, opinions, Web links, updates, and more. References to specific website topics are included throughout each chapter as well as at the end of each chapter. DevBio Laboratory: vade mecum3 : An Interactive Guide to Developmental Biology http://labs.devbio.com MARY S. TYLER and RONALD N. KOZLOWSKI copy of the textbook. (See the inside front cover for details.) DevBio Laboratory: vade mecum3 is a rich multimedia learning tool that helps students understand the development of the organisms discussed in lecture and prepares them for laboratory exercises. It also includes excerpts from the Differential Expressions series of videos, highlighting some major concepts in developmental biology, famous experiments, and the scientists who performed them. Developmental Biology: A Guide for Experimental Study, Third Edition MARY S. TYLER (Included in DevBio Laboratory: vade mecum3 ) This lab manual teaches the student to work as an independent investigator on problems in development and provides extensive background information and instructions for each experiment. It emphasizes the study of living material, intermixing developmental anatomy in an enjoyable balance, and allows the student to make choices in their work. For the Instructor (Available to qualified adopters) Instructor's Resource Library The Developmental Biology, Ninth Edition Instructor's Resource Library includes a rich collection of visual resources for use in preparing lectures and other course materials. The IRL includes: • All textbook figures (including photos) and tables in JPEG (high and low resolution) and PowerPoint® formats • A collection of videos illustrating key developmental processes • Chick embryo cross-sections and chick embryo wholemounts from DevBio Laboratory: vade mecum3 (PowerPoint® format) • Video segments from DevBio Laboratory: vade mecum3 • Instructor's Reference Guide for Differential Expressions2 New for Version 3, DevBio Laboratory: vade mecum3 is now online. Access to the program is included with every new
Also Available The following titles are available for purchase separately or, in some cases, bundled with the textbook. Please contact sinauer Associates for more Ecological Developmental Biology A Dozen Eggs Integrating Epigenetics, Medicine, and Evolution Time-Lapse Microscopy of Normal Development Scott F. Gilbert and David Epel Rachel fink Paper, 460 pages. ISBN 978-0-87893-299-3 DVD·ISBN978-0-87893-329-7 Bioethics and the New Embryology: Fly Cycle Springboards for Debate Mary S Tyler and Ronald N Kozlowski Scott F. Gilbert, Anna Tyler, and Emily Zackin DVD·ISBN978-0-87893-8490 Paper, 261 pages. ISBN 978-0-7167-7345-0 From Egg to Tadpole Differential Expressions Early Morphogenesis in Xenopus Key Experiments in Developmental Biology Jeremy D Pickett-Heaps and Julianne Pickett-Heaps Mary S. Tyler, Ronald N. Kozlowski, and Scott F. Gilbert DVD·ISBN978097752-2248 2- DVD Set·UPC855038001020
/VICUIA AINU ^urrLtivitiN i D XXI Also Available The following titles are available for purchase separately or, in some cases, bundled with the textbook. Please contact Sinauer Associates for more information. Ecological Developmental Biology: Integrating Epigenetics, Medicine, and Evolution Scott F. Gilbert and David Epel Paper, 460 pages • ISBN 978-0-87893-299-3 Bioethics and the New Embryology: Springboards for Debate Scott F. Gilbert, Anna Tyler, and Emily Zackin Paper, 261 pages • ISBN 978-0-7167-7345-0 Differential Expressions2 : Key Experiments in Developmental Biology Mary S. Tyler, Ronald N. Kozlowski, and Scott F. Gilbert 2-DVD Set • UPC 855038001020 A Dozen Eggs: Time-Lapse Microscopy of Normal Development Rachel Fink DVD • ISBN 978-0-87893-329-7 Fly Cycle2 Mary S. Tyler and Ronald N. Kozlowski DVD • ISBN 978-0-87893-849-0 From Egg to Tadpole: Early Morphogenesis in Xenopus Jeremy D. Pickett-Heaps and Julianne Pickett-Heaps DVD • ISBN 978-0-97752-224-8
°。° PART ????2 ? QUESTIONS Introducing Developmental Biolo apter etween fertilization and birth, the developing organism is known as an Developmental anatomy embryo. The concept of an embryo is a staggering one, and forming an embryo the hardest thing you will ever do. To become an embryo, you had to build apter 2 yourself from a single cell. You had to respire before you had lungs, digest Developmental genetics before you had a gut, build bones when you were pulpy, and form orderly apter 3 arrays of neurons before you knew how to think. One of the critical differences Cell-cell communication in between you and a machine is that a machine is never required to function until after it is built. Every animal has to function even as it builds itself. development For animals, fungi, and plants, the sole way of getting from egg to adult is by developing an embryo. The embryo mediates between genotype and pheno- type, between the inherited genes and the adult organism. Whereas most fields of biology study adult structure and function, developmental biology finds the study of the transient stages leading up to the adult to be more interesting Developmental biology studies the initiation and construction of organisms rather than their maintenance. It is a science of becoming, a science of process This development, this formation of an orderly body from relatively homo- geneous material, provokes profound and fundamental questions that Homo sapiens have been asking since the dawn of self-awareness: How does the body form with its head always above its shoulders? Why is the heart on the left side of our body? Why do we have five fingers on each hand and not more or fewer? Why cant we regenerate limbs? How do the sexes develop their differ ent anatomies? Why can only females have babies?
PART QUESTIONS Introducing Developmental Biology ipter 1 Developmental anatomy ipter2 Developmental genetics ipter3 Cell-cell communication in development Between fertilization and birth, the developing organism is known as an embryo. The concept of an embryo is a staggering one, and forming an embryo is the hardest thing you will ever do. To become an embryo, you had to build yourself from a single cell. You had to respire before you had lungs, digest before you had a gut, build bones when you were pulpy, and form orderly arrays of neurons before you knew how to think. One of the critical differences between you and a machine is that a machine is never required to function until after it is built. Every animal has to function even as it builds itself. For animals, fungi, and plants, the sole way of getting from egg to adult is by developing an embryo. The embryo mediates between genotype and phenotype, between the inherited genes and the adult organism. Whereas most fields of biology study adult structure and function, developmental biology finds the study of the transient stages leading up to the adult to be more interesting. Developmental biology studies the initiation and construction of organisms ralher than their maintenance. It is a science of becoming, a science of process. This development, this formation of an orderly body from relatively homogeneous material, provokes profound and fundamental questions that Homo sapiens have been asking since the dawn of self-awareness: How does the body form with its head always above its shoulders? Why is the heart on the left side of our body? Why do we have five fingers on each hand and not more or fewer? Why can't we regenerate limbs? How do the sexes develop their different anatomies? Why can only females have babies?
2 PART I Our answers to these questions must respect the complexity of the inquiry and must form a coherent causal network from gene through functional organ To say that XX mammals are usually females and that XY mammals are usually males does not explain sex determination to a developmental biologist, who wants to know how the XX genotype produces a female and how the Xy genotype pro- duces a male. Similarly, a geneticist might ask how globin genes are transmitted from one generation to the next, and a physiologist might ask about the function of globin proteins in the body. But the developmental biologist asks how it is that the globin genes come to be expressed only in red blood cells, and how these genes become active only at specific times in development. (We don' t know the answers yet. )Each field of biology is defined by the questions it asks. Welcome to nderful set of impor The Questions of Developmental Biology Development accomplishes two major objectives. First, it generates cellular diver sity and order within the individual organism; secondly, it ensures the continuity of m to the next. Put anothe there are two fundamental questions in developmental biology. How does the fertilized egg give rise to the adult body? And how does that adult body produce yet another body? These two huge questions can be subdivided into seven general categories of questions scrutinized The question of differentiation. A single cell, the fertilized egg, gives rise to hundreds of different cell types-muscle cells, epidermal cells, neurons lens cells, lymphocytes, blood cells, fat cells, and so on. The generation of this cellular diversity is called differentiation, Since every cell of the body (with very few exceptions)contains the same set of genes, how can this identical set of genetic instructions produce different types of cells? How can a single cell, the fertilized egg, generate so many different cell types?" The question of morphogenesis. How can the cells in our body organize themselves into functional structures? Our differentiated cells are not ran domly distributed. Rather, they become organized into intricate tissues and organs. During development, cells divide, migrate, and die; tissues fold and ate. Our fingers are always at the tips of our hands, never in dle; our eyes are always in our heads, not in our toes or gut. This creation of ordered form is called morphogenesis, and it involves coordinating cell The question of growth. If each cell in our face were to undergo just one more cell division, we would be considered horribly malformed. If each cell in our arms underwent just one more round of cell division, we could tie our shoelaces without bending over. How do our cells know when to stop dividing? Our arms are generally the same size on both sides of the body. How is cell division so tightly regulated? The question of reproduction. The sperm and egg are very specialized cells, and only they can transmit the instructions for making an organism There are more than 210 different cell types recognized in the adult human, but this number has little or no significance. There are many transient cell types that are formed during development but are not seen in the adult. Some of these embryonic ells are transitional stages or precursors of adult cell types. Other embryonic cell types perform particular functions in constructing an organ and then undergo pro- grammed cell death after completing their tasks
PART I Our answers to these questions must respect the complexity of the inquiry and must form a coherent causal network from gene through functional organ. To say that XX mammals are usually females and that XY mammals are usually males does not explain sex determination to a developmental biologist, who wants to know how the XX genotype produces a female and how the XY genotype produces a male. Similarly, a geneticist might ask how globin genes are transmitted from one generation to the next, and a physiologist might ask about the function of globin proteins in the body. But the developmental biologist asks how it is that the globin genes come to be expressed only in red blood cells, and how these genes become active only at specific times in development. (We don't know the answers yet.) Each field of biology is defined by the questions it asks. Welcome to a wonderful set of important questions! The Questions of Developmental Biology Development accomplishes two major objectives. First, it generates cellular diversity and order within the individual organism; secondly, it ensures the continuity of life from one generation to the next. Put another way, there are two fundamental questions in developmental biology. How does the fertilized egg give rise to the adult body? And how does that adult body produce yet another body? These two huge questions can be subdivided into seven general categories of questions scrutinized by developmental biologists: • The question of differentiation. A single cell, the fertilized egg, gives rise to hundreds of different cell types—muscle cells, epidermal cells, neurons, lens cells, lymphocytes, blood cells, fat cells, and so on. The generation of this cellular diversity is called differentiation. Since every cell of the body (with very few exceptions) contains the same set of genes, how can this identical set of genetic instructions produce different types of cells? How can a single cell, the fertilized egg, generate so many different cell types?* • The question of morphogenesis. How can the cells in our body organize themselves into functional structures? Our differentiated cells are not randomly distributed. Rather, they become organized into intricate tissues and organs. During development, cells divide, migrate, and die; tissues fold and separate. Our fingers are always at the tips of our hands, never in the middle; our eyes are always in our heads, not in our toes or gut. This creation of ordered form is called morphogenesis, and it involves coordinating cell growth, cell migration, and cell death. • The question of growth. If each cell in our face were to undergo just one more cell division, we would be considered horribly malformed. If each cell in our arms underwent just one more round of cell division, we could tie our shoelaces without bending over. How do our cells know when to stop dividing? Our arms are generally the same size on both sides of the body. How is cell division so tightly regulated? • The question of reproduction. The sperm and egg are very specialized cells, and only they can transmit the instructions for making an organism *There are more than 210 different cell types recognized in the adult human, but this number has little or no significance. There are many transient cell types that are formed during development but are not seen in the adult. Some of these embryonic cells are transitional stages or precursors of adult cell types. Other embryonic cell types perform particular functions in constructing an organ and then undergo programmed cell death after completing their tasks