1. Agenda 11/28 Start Development –watch video and do slides http://www.youtube.com/watch?v=_22CFCxDUy0 Note - during slides take notes when indicated (material that you didn’t read but you should know/study for quiz) Homework - Finish 47.3 notes, concept checks and online assignment due tomorrow Quiz Friday - 11,12, 13, 47.3 all fair game (the more you study, the better off you will be on unit test in 2 weeks)

2. Development occurs at many points in the life cycle of an animal This includes metamorphosis and gamete production, as well as embryonic development © 2011 Pearson Education, Inc.

3. Figure 47.2 EMBRYONIC DEVELOPMENT Sperm Adult frog Egg Metamorphosis Larval stages Zygote Blastula Gastrula Tail-bud embryo FERTILIZATION CLEAVAGE GASTRULATION ORGANO- GENESIS

4. Although animals display different body plans, they share many basic mechanisms of development and use a common set of regulatory genes Biologists use model organisms to study development, chosen for the ease with which they can be studied in the laboratory © 2011 Pearson Education, Inc.

5. Concept 47.1: Fertilization and cleavage initiate embryonic development Fertilization is the formation of a diploid zygote from a haploid egg and sperm © 2011 Pearson Education, Inc.

6. Fertilization Molecules and events at the egg surface play a crucial role in each step of fertilization –Sperm penetrate the protective layer around the egg –Receptors on the egg surface bind to molecules on the sperm surface –Changes at the egg surface prevent polyspermy, the entry of multiple sperm nuclei into the egg © 2011 Pearson Education, Inc.

7. Cleavage Fertilization is followed by cleavage, a period of rapid cell division without growth Cleavage partitions the cytoplasm of one large cell into many smaller cells called blastomeres The solid ball of cells is called a morula The blastula is a ball of cells with a fluid-filled cavity called a blastocoel © 2011 Pearson Education, Inc.

8. Continued cleavage produces the morula. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 47.8b

9. –Except for mammals, most animals have both eggs and zygotes with a definite polarity. Thus, the planes of division follow a specific pattern relative to the poles of the zygote. Polarity is defined by the heterogeneous distribution of substances such as mRNA, proteins, and yolk. –Yolk is most concentrated at the vegetal pole and least concentrated at the animal pole. In some animals, the animal pole defines the anterior end of the animal. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

10. A blastocoel forms within the morula  blastula Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 47.8d

11. Figure 47.6 (a) Fertilized egg (b) Four-cell stage (c) Early blastula (d) Later blastula 50  m

12. Animal embryos complete cleavage when the ratio of material in the nucleus relative to the cytoplasm is sufficiently large © 2011 Pearson Education, Inc. Regulation of Cleavage

13. After cleavage, the rate of cell division slows and the normal cell cycle is restored Morphogenesis, the process by which cells occupy their appropriate locations, involves –Gastrulation, the movement of cells from the blastula surface to the interior of the embryo –Organogenesis, the formation of organs © 2011 Pearson Education, Inc. Concept 47.2: Morphogenesis in animals involves specific changes in cell shape, position, and survival

14. Gastrulation Gastrulation rearranges the cells of a blastula into a three-layered embryo, called a gastrula © 2011 Pearson Education, Inc.

15. The three layers produced by gastrulation are called embryonic germ layers –The ectoderm forms the outer layer –The endoderm lines the digestive tract –The mesoderm partly fills the space between the endoderm and ectoderm Each germ layer contributes to specific structures in the adult animal © 2011 Pearson Education, Inc.

16. Go to study area online – Ch. 47 Watch video of sea urchin development

17. ECTODERM (outer layer of embryo) MESODERM (middle layer of embryo) ENDODERM (inner layer of embryo) Epidermis of skin and its derivatives (including sweat glands, hair follicles) Epithelial lining of digestive tract and associated organs (liver, pancreas) Epithelial lining of respiratory, excretory, and reproductive tracts and ducts Germ cells Jaws and teeth Pituitary gland, adrenal medulla Nervous and sensory systems Skeletal and muscular systems Circulatory and lymphatic systems Excretory and reproductive systems (except germ cells) Dermis of skin Adrenal cortex Thymus, thyroid, and parathyroid glands Figure 47.8

18. Gastrulation begins at the vegetal pole of the blastula Mesenchyme cells migrate into the blastocoel The vegetal plate forms from the remaining cells of the vegetal pole and buckles inward through invagination © 2011 Pearson Education, Inc. Gastrulation in Sea Urchins

19. The newly formed cavity is called the archenteron This opens through the blastopore, which will become the anus © 2011 Pearson Education, Inc.

20. Animal pole Blastocoel Mesenchyme cells Vegetal plate Vegetal pole Blastocoel Filopodia Mesenchyme cells Blastopore Archenteron 50  m Ectoderm Mouth Mesenchyme (mesoderm forms future skeleton) Blastopore Blastocoel Archenteron Digestive tube (endoderm) Anus (from blastopore) Key Future ectoderm Future mesoderm Future endoderm Figure 47.9

21. Frog gastrulation begins when a group of cells on the dorsal side of the blastula begins to invaginate This forms a crease along the region where the gray crescent formed The part above the crease is called the dorsal lip of the blastopore © 2011 Pearson Education, Inc. Gastrulation in Frogs

22. Cells continue to move from the embryo surface into the embryo by involution These cells become the endoderm and mesoderm Cells on the embryo surface will form the ectoderm © 2011 Pearson Education, Inc.

23. Key Future ectoderm Future mesoderm Future endoderm SURFACE VIEW CROSS SECTION Animal pole Vegetal pole Early gastrula Blastocoel Dorsal lip of blasto- pore Blastopore Dorsal lip of blastopore Blastocoel shrinking Archenteron Blastocoel remnant Ectoderm Mesoderm Endoderm Blastopore Yolk plug Blastopore Late gastrula 321 Figure 47.10

24. Organogenesis During organogenesis, various regions of the germ layers develop into rudimentary organs Early in vertebrate organogenesis, the notochord forms from mesoderm, and the neural plate forms from ectoderm © 2011 Pearson Education, Inc.

25. Figure 47.13 Neural folds 1 mm Neural fold Neural plate Notochord Ectoderm Mesoderm Endoderm Archenteron (a) Neural plate formation (b) Neural tube formation (c) Somites Neural fold Neural plate Neural crest cells Outer layer of ectoderm Neural crest cells Neural tube Eye SomitesTail bud SEM Neural tube Notochord Coelom Neural crest cells Somite Archenteron (digestive cavity) 1 mm

26. The neural plate soon curves inward, forming the neural tube The neural tube will become the central nervous system (brain and spinal cord) NOW – WATCH FROG DEVELOPMENT VIDEO FROM WEBSITE – ALSO FETAL ULTRASOUNDS © 2011 Pearson Education, Inc.

27. Programmed cell death is also called apoptosis At various times during development, individual cells, sets of cells, or whole tissues stop developing and are engulfed by neighboring cells For example, many more neurons are produced in developing embryos than will be needed -Extra neurons are removed by apoptosis Another example is the morphogenesis of fingers and toes (cells between undergo apoptosis) © 2011 Pearson Education, Inc. Programmed Cell Death

28. Agenda 11/29 Continue development (slides from 18.4 – this material used to be in 47.3 in old edition) through bicoid Take a study break – review/quiz each other on material below What to study for the quiz: –Cell signaling notes and diagrams in book –Mitosis/Meiosis lab and diagrams –Development notes (Powerpoint posted online) – won’t be anything on quiz that don’t get through today Start 47.3 slides – aim to get through fate mapping Homework – Study for quiz tomorrow- 11,12, 13, 47.3 all fair game (the more you study, the better off you will be on unit test in 2 weeks)

29. Concept 18.4: A program of differential gene expression leads to the different cell types in a multicellular organism During embryonic development, a fertilized egg gives rise to many different cell types Cell types are organized successively into tissues, organs, organ systems, and the whole organism Gene expression orchestrates the developmental programs of animals © 2011 Pearson Education, Inc.

30. A Genetic Program for Embryonic Development The transformation from zygote to adult results from cell division, cell differentiation, and morphogenesis © 2011 Pearson Education, Inc.

31. Figure 18.16 (a) Fertilized eggs of a frog (b) Newly hatched tadpole 1 mm 2 mm

32. Cell differentiation is the process by which cells become specialized in structure and function The physical processes that give an organism its shape constitute morphogenesis Differential gene expression results from genes being regulated differently in each cell type Materials in the egg can set up gene regulation that is carried out as cells divide © 2011 Pearson Education, Inc.

33. Cytoplasmic Determinants and Inductive Signals An egg’s cytoplasm contains RNA, proteins, and other substances that are distributed unevenly in the unfertilized egg Cytoplasmic determinants are maternal substances in the egg that influence early development As the zygote divides by mitosis, cells contain different cytoplasmic determinants, which lead to different gene expression © 2011 Pearson Education, Inc. TAKE NOTES

34. Figure 18.17a (a) Cytoplasmic determinants in the egg Unfertilized egg Sperm Fertilization Zygote (fertilized egg) Mitotic cell division Two-celled embryo Nucleus Molecules of two different cytoplasmic determinants SKETCH IN NOTES

35. The other important source of developmental information is the environment around the cell, especially signals from nearby embryonic cells In the process called induction, signal molecules from embryonic cells cause transcriptional changes in nearby target cells Thus, interactions between cells induce differentiation of specialized cell types © 2011 Pearson Education, Inc. TAKE NOTES

36. Figure 18.17b (b) Induction by nearby cells Early embryo (32 cells) NUCLEUS Signal transduction pathway Signal receptor Signaling molecule (inducer) SKETCH IN NOTES

37. © 2011 Pearson Education, Inc. Animation: Cell Signaling Right-click slide / select “Play” NICE REVIEW OF CH. 11 CELL SIGNALING

38. Sequential Regulation of Gene Expression During Cellular Differentiation Determination commits a cell to its final fate Determination precedes differentiation Cell differentiation is marked by the production of tissue-specific proteins © 2011 Pearson Education, Inc. TAKE NOTES

39. Pattern Formation: Setting Up the Body Plan Pattern formation is the development of a spatial organization of tissues and organs In animals, pattern formation begins with the establishment of the major axes Positional information, the molecular cues that control pattern formation, tells a cell its location relative to the body axes and to neighboring cells © 2011 Pearson Education, Inc. KNOW THESE VOCAB WORDS –THEY SHOULD BE IN YOUR CORNELL NOTES

40. Axis Establishment Maternal effect genes encode for cytoplasmic determinants that initially establish the axes of the body of Drosophila These maternal effect genes are also called egg- polarity genes because they control orientation of the egg and consequently the fly © 2011 Pearson Education, Inc.

41. Animation: Development of Head-Tail Axis in Fruit Flies Right-click slide / select “Play”

42. One maternal effect gene, the bicoid gene, affects the front half of the body An embryo whose mother has no functional bicoid gene lacks the front half of its body and has duplicate posterior structures at both ends Bicoid: A Morphogen Determining Head Structures © 2011 Pearson Education, Inc.

43. Figure 18.21 Head Tail Wild-type larva Mutant larva (bicoid) 250  m T1 T2 T3 A1 A2 A3 A4 A5 A6 A7 A8 A7 A6 A7 A8

44. This phenotype suggests that the product of the mother’s bicoid gene is concentrated at the future anterior end This hypothesis is an example of the morphogen gradient hypothesis, in which gradients of substances called morphogens establish an embryo’s axes and other features © 2011 Pearson Education, Inc. TAKE NOTES – KNOW BICOID EXAMPLE

45. Figure 18.22 Bicoid mRNA in mature unfertilized egg Fertilization, translation of bicoid mRNA Anterior end 100  m Bicoid protein in early embryo RESULTS

46. The bicoid research is important for three reasons –It identified a specific protein required for some early steps in pattern formation –It increased understanding of the mother’s role in embryo development –It demonstrated a key developmental principle that a gradient of molecules can determine polarity and position in the embryo © 2011 Pearson Education, Inc. PAUSE HERE FOR STUDY BREAK

47. Concept 47.3: Cytoplasmic determinants and inductive signals contribute to cell fate specification Determination is the term used to describe the process by which a cell or group of cells becomes committed to a particular fate Differentiation refers to the resulting specialization in structure and function © 2011 Pearson Education, Inc.

48. Fate Mapping Fate maps are diagrams showing organs and other structures that arise from each region of an embryo Classic studies using frogs indicated that cell lineage in germ layers is traceable to blastula cells © 2011 Pearson Education, Inc.

49. Epidermis Central nervous system Notochord Mesoderm Endoderm BlastulaNeural tube stage (transverse section) (a) Fate map of a frog embryo 64-cell embryos Blastomeres injected with dye Larvae (b) Cell lineage analysis in a tunicate Figure 47.17

50. Later studies of C. elegans used the ablation (destruction) of single cells to determine the structures that normally arise from each cell The researchers were able to determine the lineage of each of the 959 somatic cells in the worm © 2011 Pearson Education, Inc.

51. First cell division Zygote Hatching Time after fertilization (hours) Intestine Mouth EggsVulva Anus 1.2 mm ANTERIOR POSTERIOR Nervous system, outer skin, muscula- ture Muscula- ture, gonads Outer skin, nervous system Germ line (future gametes) Musculature 10 0 Figure 47.18

52. Germ cells are the specialized cells that give rise to sperm or eggs Complexes of RNA and protein are involved in the specification of germ cell fate In C. elegans, such complexes are called P granules, persist throughout development, and can be detected in germ cells of the adult worm P granules act as cytoplasmic determinants, fixing germ cell fate at the earliest stage of development © 2011 Pearson Education, Inc.

53. Figure 47.20 Newly fertilized egg Zygote prior to first division Two-cell embryo Four-cell embryo 20  m 2134

54. Figure 47.19 100  m

55. Axis Formation A body plan with bilateral symmetry is found across a range of animals This body plan exhibits asymmetry across the dorsal-ventral and anterior-posterior axes The right-left axis is largely symmetrical © 2011 Pearson Education, Inc.

56. The anterior-posterior axis of the frog embryo is determined during oogenesis The animal-vegetal asymmetry indicates where the anterior-posterior axis forms (animal is embryo, vegetal is yolk) The dorsal-ventral axis is not determined until fertilization © 2011 Pearson Education, Inc.

57. Upon fusion of the egg and sperm, the egg surface rotates with respect to the inner cytoplasm This cortical rotation brings molecules from one area of the inner cytoplasm of the animal hemisphere to interact with molecules in the vegetal cortex This leads to expression of dorsal- and ventral- specific gene expression © 2011 Pearson Education, Inc.

58. Dorsal Right AnteriorPosterior Ventral Left (a) The three axes of the fully developed embryo (b) Establishing the axes Animal hemisphere Vegetal hemisphere Animal pole Vegetal pole Point of sperm nucleus entry Gray crescent Pigmented cortex Future dorsal side First cleavage Figure 47.21

59. In chicks, gravity is involved in establishing the anterior-posterior axis Later, pH differences between the two sides of the blastoderm establish the dorsal-ventral axis In mammals, experiments suggest that orientation of the egg and sperm nuclei before fusion may help establish embryonic axes © 2011 Pearson Education, Inc.

60. Restricting Developmental Potential Hans Spemann performed experiments to determine a cell’s developmental potential (range of structures to which it can give rise) Embryonic fates are affected by distribution of determinants and the pattern of cleavage The first two blastomeres of the frog embryo are totipotent (can develop into all the possible cell types) © 2011 Pearson Education, Inc.

61. Control egg (dorsal view) 1a1b Gray crescent Control group Experimental group Experimental egg (side view) Gray crescent EXPERIMENT Thread Figure 47.22-1

62. Control egg (dorsal view) 2 1a1b Gray crescent Control group Experimental group Experimental egg (side view) Gray crescent Thread Normal Belly piece EXPERIMENT RESULTS Figure 47.22-2

63. In mammals, embryonic cells remain totipotent until the 8-cell stage, much longer than other organisms Progressive restriction of developmental potential is a general feature of development in all animals In general tissue-specific fates of cells are fixed by the late gastrula stage © 2011 Pearson Education, Inc.

64. Cell Fate Determination and Pattern Formation by Inductive Signals As embryonic cells acquire distinct fates, they influence each other’s fates by induction © 2011 Pearson Education, Inc.

65. The “Organizer” of Spemann and Mangold Spemann and Mangold transplanted tissues between early gastrulas and found that the transplanted dorsal lip triggered a second gastrulation in the host The dorsal lip functions as an organizer of the embryo body plan, inducing changes in surrounding tissues to form notochord, neural tube, and so on © 2011 Pearson Education, Inc.

66. Figure 47.23 Dorsal lip of blastopore Pigmented gastrula (donor embryo) Nonpigmented gastrula (recipient embryo) Primary embryo Secondary (induced) embryo Primary structures: Neural tube Notochord Secondary structures: Notochord (pigmented cells) Neural tube (mostly nonpigmented cells) EXPERIMENT RESULTS

67. Formation of the Vertebrate Limb Inductive signals play a major role in pattern formation, development of spatial organization The molecular cues that control pattern formation are called positional information This information tells a cell where it is with respect to the body axes It determines how the cell and its descendents respond to future molecular signals © 2011 Pearson Education, Inc.

68. The wings and legs of chicks, like all vertebrate limbs, begin as bumps of tissue called limb buds © 2011 Pearson Education, Inc.

69. Figure 47.24 Limb buds 50  m Anterior Limb bud AER ZPA Posterior Apical ectodermal ridge (AER) (a) Organizer regions (b) Wing of chick embryo Digits Anterior Proximal Dorsal Posterior Ventral Distal 2 3 4

70. The embryonic cells in a limb bud respond to positional information indicating location along three axes –Proximal-distal axis –Anterior-posterior axis –Dorsal-ventral axis © 2011 Pearson Education, Inc.

71. One limb bud–regulating region is the apical ectodermal ridge (AER) The AER is thickened ectoderm at the bud’s tip The second region is the zone of polarizing activity (ZPA) The ZPA is mesodermal tissue under the ectoderm where the posterior side of the bud is attached to the body © 2011 Pearson Education, Inc.

72. Tissue transplantation experiments support the hypothesis that the ZPA produces an inductive signal that conveys positional information indicating “posterior” © 2011 Pearson Education, Inc.

73. Figure 47.25 Donor limb bud Host limb bud ZPA Anterior Posterior New ZPA 4 4 3 3 2 2 EXPERIMENT RESULTS

74. Sonic hedgehog is an inductive signal for anterior/posterior limb development – gradient from ZPA Hox genes also play roles during limb pattern formation © 2011 Pearson Education, Inc.

75. Cilia and Cell Fate Ciliary function is essential for proper specification of cell fate in the human embryo Motile cilia play roles in left-right specification (always sweep fluid to the left, creating slight asymmetry of morphogens on left-right axis) Monocilia (nonmotile cilia) are on every cell and act as antenna to receive signal proteins (such as Sonic hedgehog) –play roles in normal kidney development © 2011 Pearson Education, Inc.

76. Figure 47.26 Lungs Heart Liver Spleen Stomach Large intestine Normal location of internal organs Location in situs inversus Caused by defect in motile cilia in a particular part of the embryo