1. The most complex problem
How to get from here

2. The most complex problem
How to get from here to there

3. Chapter 47
Animal Development

4. A human embryo at about 7 weeks after conception
Figure 47.1
Figure 47.1 How did a single cell develop into this intricately detailed embryo?
A human embryo at about 7 weeks after conception
shows development of distinctive features
1 mm

5. Development: cellular level
Cell division
Differentiation
cells become specialized in structure & function
Morphogenesis (organogenesis)

6. Development: cellular level
Cell division
Differentiation
cells become specialized in structure & function
if each kind of cell has the same genes, how can they be so different?
shutting off of genes = loss of totipotency
Turning genes on based on chemical cues
Morphogenesis (organogenesis)

7. Development: cellular level
Cell division
Differentiation
cells become specialized in structure & function
if each kind of cell has the same genes, how can they be so different?
shutting off of genes = loss of totipotency
Turning genes on based on chemical cues
Morphogenesis (organogenesis)
“creation of form” = give organism shape
basic body plan
polarity
one end is different than the other
symmetry
left & right side of body mirror each other
asymmetry
look at your hand…

8. Our model organisms

9. EMBRYONIC DEVELOPMENT Sperm
Developmental events
EMBRYONIC DEVELOPMENT
Sperm
Zygote
Adult frog
Egg
FERTILIZATION
CLEAVAGE
Metamorphosis
Blastula
GASTRULATION
Figure 47.2 Developmental events in the life cycle of a frog.
ORGANO- GENESIS
Larval stages
Gastrula
Tail-bud embryo

10. Fertilization in sea urchins: fast block and slow block to polyspermy
Basal body (centriole)
Sperm head
Figure 47.3 The acrosomal and cortical reactions during sea urchin fertilization.
Acrosome
Jelly coat
Vitelline layer
Sperm-binding receptors
Egg plasma membrane

11. Basal body (centriole)
Figure
Basal body (centriole)
Sperm head
Figure 47.3 The acrosomal and cortical reactions during sea urchin fertilization.
Acrosome
Hydrolytic enzymes
Jelly coat
Vitelline layer
Sperm-binding receptors
Egg plasma membrane

12. Basal body (centriole)
Figure
Sperm nucleus
Acrosomal process
Basal body (centriole)
Actin filament
Sperm head
Figure 47.3 The acrosomal and cortical reactions during sea urchin fertilization.
Acrosome
Hydrolytic enzymes
Jelly coat
Vitelline layer
Sperm-binding receptors
Egg plasma membrane

13. Basal body (centriole)
Figure
Sperm plasma membrane
Sperm nucleus
Acrosomal process
Basal body (centriole)
Actin filament
Sperm head
Fused plasma membranes
Figure 47.3 The acrosomal and cortical reactions during sea urchin fertilization.
Acrosome
Hydrolytic enzymes
Jelly coat
Vitelline layer
Sperm-binding receptors
Egg plasma membrane

14. Fertilization envelope
Figure
Sperm plasma membrane
Sperm nucleus
Fertilization envelope
Acrosomal process
Basal body (centriole)
Actin filament
Sperm head
Cortical granule
Fused plasma membranes
Figure 47.3 The acrosomal and cortical reactions during sea urchin fertilization.
Acrosome
Hydrolytic enzymes
Perivitelline space
Jelly coat
Vitelline layer
Sperm-binding receptors
EGG CYTOPLASM
Egg plasma membrane

15. Slow block to polyspermy: Change in Ca++ in the egg makes f.e.
EXPERIMENT
Slow block to polyspermy: Change in Ca++ in the egg makes f.e.
10 sec after fertilization
25 sec
35 sec
1 min
500 m
RESULTS
1 sec before fertilization
10 sec after fertilization
20 sec
30 sec
500 m
Figure 47.4 Inquiry: Does the distribution of Ca2 in an egg correlate with formation of the fertilization envelope?
CONCLUSION
Fertilization envelope
Point of sperm nucleus entry
Spreading wave of Ca2

16. Egg Activation
The rise in Ca2+ in the cytosol increases the rates of cellular respiration and protein synthesis by the egg cell
With these rapid changes in metabolism, the egg is said to be activated
The proteins and mRNAs needed for activation are already present in the egg
The sperm nucleus merges with the egg nucleus and cell division begins
© 2011 Pearson Education, Inc.

17. When the sperm binds a receptor in the zona pellucida, it triggers a slow block to polyspermy (no fast block to polyspermy has been identified in mammals)
Zona pellucida
Follicle cell
Figure 47.5 Fertilization in mammals.
Sperm nucleus
Cortical granules
Sperm basal body

18. 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 blastula is a ball of cells with a fluid-filled cavity called a blastocoel
50 m
(a) Fertilized egg
(b) Four-cell stage
(c) Early blastula
(d) Later blastula
Figure 47.6 Cleavage in an echinoderm embryo.

19. Cleavage in a frog embryo
Zygote
2-cell stage forming
Gray crescent
0.25 mm
8-cell stage (viewed from the animal pole)
4-cell stage forming
Animal pole
8-cell stage
Figure 47.7 Cleavage in a frog embryo.
0.25 mm
Blastula (at least 128 cells)
Vegetal pole
Blastocoel
Blastula (cross section)

20. Concept 47.2: Morphogenesis in animals involves specific changes in cell shape, position, and survival
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.

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

22. Gastrulation in the sea urchin
Animal pole
Blastocoel
Mesenchyme cells
Vegetal plate
Vegetal pole
Blastocoel
Filopodia
Mesenchyme cells
Archenteron
Blastopore
Figure 47.9 Gastrulation in a sea urchin embryo.
50 m
Blastocoel
Ectoderm
Archenteron
Key
Blastopore
Mouth
Future ectoderm
Mesenchyme (mesoderm forms future skeleton)
Digestive tube (endoderm)
Future mesoderm
Anus (from blastopore)
Future endoderm

23. Gastrulation in frog embryo
SURFACE VIEW
CROSS SECTION
Animal pole 1
Blastocoel
Dorsal lip of blasto- pore
Dorsal lip of blastopore
Blastopore
Early gastrula
Vegetal pole 2
Blastocoel shrinking
Archenteron
Figure Gastrulation in a frog embryo.
Ectoderm 3
Blastocoel remnant
Mesoderm
Endoderm
Key
Future ectoderm
Blastopore
Future mesoderm
Late gastrula
Yolk plug
Archenteron
Blastopore
Future endoderm

24. Gastrulation in chicks
Fertilized egg
Primitive streak
Embryo
Yolk
Primitive streak
Epiblast
Future ectoderm
Figure Gastrulation in a chick embryo.
Blastocoel
Migrating cells (mesoderm)
Endoderm
Hypoblast
YOLK

25. Embryonic development in humans1
Blastocyst reaches uterus.
Endometrial epithelium (uterine lining)
Inner cell mass
Uterus
Trophoblast
Blastocoel 2
Blastocyst implants (7 days after fertilization).
Expanding region of trophoblast
Maternal blood vessel
Epiblast
Hypoblast
Trophoblast
Expanding region of trophoblast 3
Extraembryonic membranes start to form (10–11 days), and gastrulation begins (13 days).
Amniotic cavity
Epiblast
Hypoblast
Yolk sac (from hypoblast)
Extraembryonic mesoderm cells (from epiblast)
Figure Four stages in the early embryonic development of a human.
Chorion (from trophoblast) 4
Gastrulation has produced a three-layered embryo with four extraembryonic membranes.
Amnion
Chorion
Ectoderm
Mesoderm
Endoderm
Yolk sac
Extraembryonic mesoderm
Allantois

26. Endometrial epithelium (uterine lining)
Figure 47.12a
Endometrial epithelium (uterine lining)
Inner cell mass
Uterus
Trophoblast
Blastocoel
Figure Four stages in the early embryonic development of a human. 1
Blastocyst reaches uterus.

27. Expanding region of trophoblast
Figure 47.12b
Expanding region of trophoblast
Maternal blood vessel
Epiblast
Hypoblast
Trophoblast
Figure Four stages in the early embryonic development of a human. 2
Blastocyst implants (7 days after fertilization).

28. Expanding region of trophoblast
Figure 47.12c
Expanding region of trophoblast
Amniotic cavity
Epiblast
Hypoblast
Yolk sac (from hypoblast)
Extraembryonic mesoderm cells (from epiblast)
Chorion (from trophoblast)
Figure Four stages in the early embryonic development of a human. 3
Extraembryonic membranes start to form (10–11 days), and gastrulation begins (13 days).

29. Extraembryonic mesoderm
Figure 47.12d
Amnion
Chorion
Ectoderm
Mesoderm
Endoderm
Yolk sac
Extraembryonic mesoderm
Allantois
Figure Four stages in the early embryonic development of a human. 4
Gastrulation has produced a three-layered embryo with four extraembryonic membranes.

30. Developmental Adaptations of Amniotes
The colonization of land by vertebrates was made possible only after the evolution of
The shelled egg of birds and other reptiles as well as monotremes (egg-laying mammals)
The uterus of marsupial and eutherian mammals
© 2011 Pearson Education, Inc.

31. The four extraembryonic membranes that form around the embryo in a reptile/bird:
The chorion functions in gas exchange
The amnion encloses the amniotic fluid
The yolk sac encloses the yolk
The allantois disposes of waste products and contributes to gas exchange
© 2011 Pearson Education, Inc.

32. Neuralation in a frog embryo
Neural folds
Eye
Somites
Tail bud
Neural fold
Neural plate
SEM
1 mm
1 mm
Neural tube
Neural crest cells
Neural fold
Neural plate
Notochord
Neural crest cells
Coelom
Notochord
Ectoderm
Somite
Figure Neurulation in a frog embryo.
Mesoderm
Outer layer of ectoderm
Archenteron (digestive cavity)
Endoderm
Neural crest cells
(c) Somites
Archenteron
(a) Neural plate formation
Neural tube
(b) Neural tube formation

33. Organogenisis in a chick
Neural tube
Eye
Notochord
Forebrain
Somite
Archenteron
Coelom
Heart
Lateral fold
Endoderm
Mesoderm
Blood vessels
Ectoderm
Somites
Yolk stalk
Yolk sac
These layers form extraembryonic membranes.
Figure Organogenesis in a chick embryo.
Neural tube
YOLK
(a) Early organogenesis
(b) Late organogenesis

34. Morpho-genesis results from cells changing shape
Ectoderm
Figure Change in cell shape during morphogenesis.

35. Ectoderm Neural plate Microtubules Figure 47.15-2
Figure Change in cell shape during morphogenesis.

36. Ectoderm Neural plate Microtubules Actin filaments Figure 47.15-3
Figure Change in cell shape during morphogenesis.

37. Ectoderm Neural plate Microtubules Actin filaments Figure 47.15-4
Figure Change in cell shape during morphogenesis.

38. Ectoderm Neural plate Microtubules Actin filaments Neural tube
Figure
Ectoderm
Neural plate
Microtubules
Actin filaments
Figure Change in cell shape during morphogenesis.
Neural tube

39. Elongation of tissue by convergent extension
Convergence
Extension
Figure Convergent extension of a sheet of cells.

40. Concept 47.3: What determines how parts form; and messing with those determining factors
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
Can result from: oocyte composition, logal signals, gravity
© 2011 Pearson Education, Inc.

41. Blastomeres injected with dye
Fate mapping
Epidermis
Epidermis
Central nervous system
Notochord
Mesoderm
Endoderm
Blastula
Neural tube stage (transverse section)
(a) Fate map of a frog embryo
64-cell embryos
Figure Fate mapping for two chordates.
Blastomeres injected with dye
Larvae
(b) Cell lineage analysis in a tunicate

42. Time after fertilization (hours)
Figure 47.18
Zygote
First cell division
Nervous system, outer skin, muscula- ture
Muscula- ture, gonads
Outer skin, nervous system
Germ line (future gametes)
Time after fertilization (hours)
Musculature 10
Hatching
Intestine
Figure Cell lineage in Caenorhabditis elegans.
Intestine
Anus
Mouth
Eggs
Vulva
ANTERIOR
POSTERIOR
1.2 mm

43. Determination of germ cell fate in C. elegans.
Figure Determination of germ cell fate in C. elegans.

44. Experimental egg (side view)
How does distribution of the gray crescent affect the developmental potential of the first two daughter cells?
EXPERIMENT
Control egg (dorsal view)
Experimental egg (side view) 1a
Control group 1b
Experimental group
Gray crescent
Gray crescent
Thread
Figure Inquiry: How does distribution of the gray crescent affect the developmental potential of the first two daughter cells? 2
RESULTS
Normal
Belly piece
Normal

45. 8-cell stage (viewed from the animal pole)
Figure 47.7b
0.25 mm
Animal pole
Figure 47.7 Cleavage in a frog embryo.
8-cell stage (viewed from the animal pole)

46. Blastula (at least 128 cells)
Figure 47.7c
0.25 mm
Blastocoel
Figure 47.7 Cleavage in a frog embryo.
Blastula (at least 128 cells)

47. Dorsal lip of blastopore Primary embryo
Can the dorsal lip of the blastopore induce cells in another part of the amphibian embryo to change their developmental fate?
EXPERIMENT
RESULTS
Dorsal lip of blastopore
Primary embryo
Secondary (induced) embryo
Pigmented gastrula (donor embryo)
Primary structures:
Nonpigmented gastrula (recipient embryo)
Neural tube
Notochord
Figure Inquiry: Can the dorsal lip of the blastopore induce cells in another part of the amphibian embryo to change their developmental fate?
Secondary structures:
Notochord (pigmented cells)
Neural tube (mostly nonpigmented cells)

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

49. 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.

50. What happens when you put ZPA on both sides of a budding limb?
EXPERIMENT
Anterior
New ZPA
Donor limb bud
Host limb bud
ZPA
Posterior
RESULTS
What happens when you put ZPA on both sides of a budding limb?
Figure Inquiry: What role does the zone of polarizing activity (ZPA) play in limb pattern formation in vertebrates?

51. Could you make a human with pinkies on both sides of their hands?

52. EXPERIMENT Anterior New ZPA Donor limb bud Host limb bud ZPA Posterior
What role does the zone of polarizing activity (ZPA) play in limb pattern formation in vertebrates?
EXPERIMENT
Anterior
New ZPA
Donor limb bud
Host limb bud
ZPA
Posterior
RESULTS 4
Figure Inquiry: What role does the zone of polarizing activity (ZPA) play in limb pattern formation in vertebrates? 3 2 2 3 4

53. Sonic hedgehog is an inductive signal for limb development
Hox genes also play roles during limb pattern formation
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.

54. Homeotic genes
Mutations to homeotic genes produce flies with such strange traits as legs growing from the head in place of antennae.
structures characteristic of a particular part of the animal arise in wrong place
antennapedia flies

55. Homeobox DNA Master control genes evolved early
Conserved for hundreds of millions of years
Homologous homeobox genes in fruit flies & vertebrates
kept their chromosomal arrangement

56. 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
Monocilia (nonmotile cilia) play roles in normal kidney development
© 2011 Pearson Education, Inc.

57. Normal location of internal organs Location in situs inversus
Figure 47.26
Lungs
Heart
Liver
Spleen
Stomach
Figure Situs inversus, a reversal of normal left-right asymmetry in the chest and abdomen.
Large intestine
Normal location of internal organs
Location in situs inversus