the most complex problem how to get from here. the most complex problem how to get from here to...

The most complex problem

How to get from here

The most complex problem

How to get from here to there

LECTURE PRESENTATIONSFor CAMPBELL BIOLOGY, NINTH EDITION

Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson

© 2011 Pearson Education, Inc.

Lectures byErin Barley

Kathleen Fitzpatrick

Animal Development

Chapter 47

Figure 47.1

1 mm

A human embryo at about 7 weeks after conception shows development of distinctive features

Development: cellular level • Cell division• Differentiation

– cells become specialized in structure & function

• Morphogenesis (organogenesis)


– 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)


– 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…

Our model organisms

Developmental events

EMBRYONIC DEVELOPMENTSperm

Adultfrog

Egg

Metamorphosis

Larvalstages

Zygote

Blastula

Gastrula

Tail-budembryo

FE

RT

ILIZ

AT

ION

CLEAVAGE

GASTRULATION

OR

GA

NO

-

GE

NE

SIS

Fertilization in sea urchins: fast block and slow block to polyspermy

Basal body(centriole)

Spermhead

Acrosome

Jelly coat

Sperm-bindingreceptors

Vitelline layer

Egg plasma membrane

Figure 47.3-2


Spermhead

Acrosome

Jelly coat


Hydrolytic enzymesVitelline layer

Egg plasma membrane

Figure 47.3-3


Spermnucleus

Spermhead

Acrosome

Jelly coat



Egg plasma membrane

Actinfilament

Acrosomalprocess

Figure 47.3-4


Spermplasmamembrane

Spermnucleus

Spermhead

Acrosome

Jelly coat


Fusedplasmamembranes


Egg plasma membrane

Actinfilament

Acrosomalprocess

Figure 47.3-5


Spermplasmamembrane

Spermnucleus

Spermhead

Acrosome

Jelly coat


Fertilizationenvelope

Corticalgranule

Fusedplasmamembranes


Egg plasma membrane

Perivitellinespace

EGG CYTOPLASM

Actinfilament

Acrosomalprocess

Slow block to polyspermy: Change in Ca++ in the egg makes f.e.

10 sec afterfertilization

25 sec 35 sec 1 min500 m

500 m30 sec20 sec10 sec after

fertilization1 sec beforefertilization

Point of spermnucleusentry

Spreadingwave of Ca2

Fertilizationenvelope

EXPERIMENT

RESULTS

CONCLUSION

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


Zona pellucida

Follicle cell

Spermbasal body

Spermnucleus

Corticalgranules

• 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)

(a) Fertilized egg (b) Four-cell stage (c) Early blastula (d) Later blastula

50 m

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

Zygote

2-cellstageforming

4-cellstageforming

8-cellstage

Vegetal pole

Blastula(crosssection)

Gray crescent

Animalpole

Blastocoel

0.25 mm

0.25 mm

8-cell stage (viewedfrom the animal pole)

Blastula (at least 128 cells)

Cleavage in a frog embryo

• 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


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

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

Animalpole

Blastocoel

Mesenchymecells

Vegetal plateVegetalpole

Blastocoel

Filopodia

Mesenchymecells

Blastopore

Archenteron

50 m

Ectoderm

Mouth

Mesenchyme(mesoderm formsfuture skeleton)

Blastopore

Blastocoel

Archenteron

Digestive tube (endoderm)

Anus (from blastopore)

Key

Future ectodermFuture mesodermFuture endoderm

Gastrulation in the sea urchin

Key

Future ectodermFuture mesodermFuture endoderm

SURFACE VIEW CROSS SECTIONAnimal pole

Vegetal poleEarlygastrula

Blastocoel

Dorsal lip ofblasto-pore

BlastoporeDorsal lip ofblastopore

Blastocoelshrinking

Archenteron

Archenteron

Blastocoelremnant

EctodermMesodermEndoderm

Blastopore

Yolk plugBlastopore

Lategastrula

3

2

1

Gastrulation in frog embryo

Future ectoderm

Migratingcells(mesoderm)

Blastocoel

Epiblast

YOLK

EndodermHypoblast

Primitive streak

Fertilized eggPrimitivestreak

Embryo

Yolk

Gastrulation in chicks

Blastocyst reaches uterus.1

2

3

4

Blastocyst implants(7 days after fertilization).

Extraembryonic membranesstart to form (10–11 days),and gastrulation begins(13 days).

Gastrulation has produced athree-layered embryo withfour extraembryonicmembranes.

Uterus

Maternal bloodvessel

Endometrial epithelium(uterine lining)

Inner cell mass

Trophoblast

Blastocoel

Expanding region oftrophoblast

EpiblastHypoblast

Trophoblast


Amniotic cavity

EpiblastHypoblast

Yolk sac (from hypoblast)

Extraembryonic mesoderm cells(from epiblast)

Chorion (from trophoblast)

AmnionChorionEctodermMesoderm

EndodermYolk sac

Extraembryonic mesoderm

Allantois

Embryonic development in humans

Figure 47.12a

Blastocyst reaches uterus.1

Uterus

Endometrial epithelium(uterine lining)

Inner cell mass

Trophoblast

Blastocoel

Figure 47.12b

Blastocyst implants(7 days after fertilization).

Maternal bloodvessel


Epiblast

Hypoblast

Trophoblast

2

Figure 47.12c

Extraembryonic membranesstart to form (10–11 days),and gastrulation begins(13 days).


Amniotic cavity

Epiblast

HypoblastYolk sac (from hypoblast)

Extraembryonic mesoderm cells (from epiblast)

Chorion (from trophoblast)3

Figure 47.12d

Gastrulation has produced athree-layered embryo withfour extraembryonicmembranes.

AmnionChorionEctodermMesoderm

Endoderm

Yolk sac

Extraembryonic mesoderm

Allantois

4

Developmental Adaptations of Amniotes

• The colonization of land by vertebrates was made possible only after the evolution of1. The shelled egg of birds and other reptiles as

well as monotremes (egg-laying mammals)

2. The uterus of marsupial and eutherian mammals


• 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


Neuralation in a frog embryo

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 layerof ectoderm

Neural crest cells

Neural tube

Eye Somites Tail bud

SEM

Neural tube

Notochord

Coelom

Neuralcrestcells

Somite

Archenteron(digestivecavity)

1 mm

Organogenisis in a chick

Neural tube

Notochord

Archenteron

Lateral fold

These layersform extraembryonicmembranes.

Yolk stalk

YOLK

Yolk sac

Somite

Coelom

EndodermMesodermEctoderm

(a) Early organogenesis (b) Late organogenesis

Eye

Forebrain

Heart

Bloodvessels

Somites

Neuraltube

Morpho-genesis results from cells changing shape

Ectoderm

Figure 47.15-2 Ectoderm

Neuralplate

Microtubules


Neuralplate

Microtubules

Actinfilaments


Neuralplate

Microtubules

Actinfilaments

Neural tube

Elongation of tissue by convergent extension

ExtensionConvergence

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


Epidermis EpidermisCentralnervoussystemNotochord

Mesoderm

Endoderm

Blastula Neural tube stage(transverse section)

(a) Fate map of a frog embryo

64-cell embryos

Blastomeresinjected with dye

Larvae

(b) Cell lineage analysis in a tunicate

Fate mapping

First cell divisionZygote

HatchingTim

e a

fter

fer

tiliz

ati

on

(h

ou

rs)

Intestine

Intestine

MouthEggs Vulva

Anus

1.2 mmANTERIOR POSTERIOR

Nervoussystem,outer skin,muscula-ture

Muscula-ture, gonads

Outer skin,nervous system

Germ line(futuregametes)

Musculature

10

0Figure 47.18

Determination of germ cell fate in C. elegans.

100 m

Control egg(dorsal view)

2

1a 1b

Graycrescent

Controlgroup

Experimentalgroup

Experimental egg(side view)

Graycrescent

Thread

Normal NormalBelly piece

EXPERIMENT

RESULTS

How does distribution of the gray crescent affect the developmental potential of the first two daughter cells?

Figure 47.7b

Animalpole

0.25 mm

8-cell stage (viewedfrom the animal pole)

Figure 47.7c

0.25 mm

Blastocoel

Blastula (at least 128 cells)

Can the dorsal lip of the blastopore induce cells in another part of the amphibian embryo to change their developmental fate?

Dorsal lip ofblastopore

Pigmentedgastrula

(donor embryo)Nonpigmented

gastrula(recipient embryo)

Primary embryo

Secondary (induced) embryo

Primary structures:Neural tubeNotochord

Secondary structures:Notochord (pigmented cells)Neural tube(mostly nonpigmented cells)

EXPERIMENT RESULTS

Figure 47.24

Limb buds

50 m

AnteriorLimb bud

AER

ZPA

Posterior

Apicalectodermalridge (AER)

(a) Organizer regions (b) Wing of chick embryo

Digits

Anterior

Proximal

Dorsal

Posterior

Ventral

Distal

2

34

• 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


Donorlimbbud

Hostlimbbud

ZPA

Anterior

Posterior

New ZPA

EXPERIMENT

RESULTS

What happens when you put ZPA on both sides of a budding limb?

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

What role does the zone of polarizing activity (ZPA) play in limb pattern formation in vertebrates?

Donorlimbbud

Hostlimbbud

ZPA

Anterior

Posterior

New ZPA

4

4

3

3

2 2

EXPERIMENT

RESULTS

• 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.

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 placeantennapedia flies

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

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


Figure 47.26

Lungs

Heart

Liver

Spleen

Stomach

Large intestine

Normal locationof internal organs

Location insitus inversus

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kind of cell

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rates of cellular respiration

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