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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

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



Echinoderms

Chordates

Annelids

Arthropods

Mollusks

Protostomes

Deuterostomes

Acoelomates

TIME


EGG

MORULA




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 47.8

FROG

BLASTULA



Frog blastula

blastocoel

Dorsal lip.

The invagination for gastrulation starts here





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





Tadpole

Aquatic

Gills

Herbivorous

Swimming

Frog

Terrestrial

Lungs

Carnivorous

Jumping

metamorphosis



Fig. 21.23 development?

Development in the fly


Fig. 21.24 development?

Determination of anterior -

posterior axis in the fly



Bigger is better! plasticity

Pond dries,

metamorphosis

or death

larger

Size of

tadpole

smaller

Time


Stage 36 plasticity

C

O

Stage 27

C

20 mm

20 mm

O

Stage 42

C

O

Omnivore

Carnivore


Comparison of beaks of spadefoot tadpoles plasticity

Omnivore

Carnivore


larger plasticity

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 change the timing of development and metamorphosis: this provides an avenue for evolutionary innovation


Amphioxus change the timing of development and metamorphosis: this provides an avenue for evolutionary innovation

Larva

Heterochrony

Neoteny

Paedomorphosis

Adult



Lake Apopka development


higher development

Concentration

of toxins in

water

lower

Lake Woodruff

Lake Apopka


larger development

Alligator

penis

size

smaller

Lake Woodruff

Lake Apopka


larger development

Alligator

penis

size

smaller

lower

higher

Concentration of toxins in water



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