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OUTLINE 6 VI. Morphogenesis A. General features of gastrulation B. Cell movement 1. extension and contraction 2. adhesion C. Gastrulation in the sea urchin D. Gastrulation in the frog E. Three layers of cells 1. ectoderm 2. mesoderm 3. endoderm F. Neurulation.

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OUTLINE 6 VI. Morphogenesis A. General features of gastrulation B. Cell movement

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OUTLINE 6

VI. Morphogenesis

A. General features of gastrulation

B. Cell movement

1. extension and contraction

2. adhesion

C. Gastrulation in the sea urchin

D. Gastrulation in the frog

E. Three layers of cells

1. ectoderm

2. mesoderm

3. endoderm

F. Neurulation


animal pole

vegetal pole


After this point, Protostomes and Deuterostomes depart


Echinoderms

Chordates

Annelids

Arthropods

Mollusks

Protostomes

Deuterostomes

Acoelomates

TIME


EGG

MORULA


SEA URCHIN BLASTULA


Fig 47.16


Fig 47.9

Animal pole

Blastocoel

Vegetal pole

Start of invagination

(blastopore)


Fig 47.9

Archenteron


Fig 47.9

Archenteron

Mouth

Digestive tract

Anus


Fig 47.9

Archenteron

endoderm

ectoderm

mesoderm


Fig 47.7


Fig 47.7


Fig 47.8

FROG

BLASTULA


Fig 47.10


Frog blastula

blastocoel

Dorsal lip.

The invagination for gastrulation starts here


Fig 47.10


Fig 47.10


Fig 47.10


Scanning

Election

Micrographs


Fig. 47.11

Neurulation in the frog


OUTLINE 7

VII. Mechanisms of Animal Development

A. Cytoplasmic determinants

1. axes of symmetry in amphibians

2. bicoid gene in Drosophila

B. Cell communication

1. Holtfreter’s work

2. mechanisms of cell recognition

3. induction

C. Morphogens and pattern formation (chick limb bud)

D. Hormones (in amphibian development)

1. pattern of metamorphosis

2. role of thyroxin

3. evidence


ectoderm

mesoderm

endoderm

1. dissociation

3. resegregation

2. reaggregation

Holtfretter 1955


Spemann and Mangold: an organizer

Fig. 47.22


Pattern formation: the chick limb bud

Fig. 47.24


Pattern formation: the chick limb bud

Fig. 47.24


Tadpole

Aquatic

Gills

Herbivorous

Swimming

Frog

Terrestrial

Lungs

Carnivorous

Jumping

metamorphosis


How do hormones turn on and off the genes that control development?


Fig. 21.23

Development in the fly


Fig. 21.24

Determination of anterior -

posterior axis in the fly


Natural variation in hormone levels can cause developmental plasticity


Bigger is better!

Pond dries,

metamorphosis

or death

larger

Size of

tadpole

smaller

Time


Stage 36

C

O

Stage 27

C

20 mm

20 mm

O

Stage 42

C

O

Omnivore

Carnivore


Comparison of beaks of spadefoot tadpoles

Omnivore

Carnivore


larger

Size of

tadpole

smaller

Time

Pond dries,

metamorphosis


Natural and experimental variation in hormone levels can change the timing of development and metamorphosis: this provides an avenue for evolutionary innovation


Evolution of Vertebrate body plan


Amphioxus

Larva

Heterochrony

Neoteny

Paedomorphosis

Adult


Chemical pollutants can influence hormones and alter development


Lake Apopka


higher

Concentration

of toxins in

water

lower

Lake Woodruff

Lake Apopka


larger

Alligator

penis

size

smaller

Lake Woodruff

Lake Apopka


larger

Alligator

penis

size

smaller

lower

higher

Concentration of toxins in water


Effects of Atrazine on frog development


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