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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. - PowerPoint PPT Presentation
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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
Acoelomates
ProtostomesDeuterostomes
Arthropods Mollusks Annelids Echinoderms Chordates
TIME
Mouth develops:
First Second
Cleavage planes:
Spiral Radial
Early development:
Not totipotent Totipotent
MORULA
EGG
SEA URCHIN
BLASTULA
Fig 47.16
Fig 47.9
Animal pole
Vegetal pole
Blastocoel
Start of invagination(blastopore)
Fig 47.9
Archenteron
Fig 47.9
Mouth
Anus
Archenteron
Digestive tract
Fig 47.9
ectodermmesoderm
Archenteron
endoderm
Fig 47.7
Fig 47.7
Fig 47.8
FROGBLASTULA
Fig 47.10
Frog blastula
blastocoel
Dorsal lip.The invagination for gastrulation starts here
Fig 47.10
Fig 47.10
Fig 47.10
ScanningElectionMicrographs
Fig. 47.11
Neurulation in the frog
OUTLINE 7VII. Mechanisms of Animal Development
A. Cytoplasmic determinants1. axes of symmetry in amphibians2. bicoid gene in Drosophila
B. Cell communication1. Holtfreter’s work2. mechanisms of cell recognition3. induction
C. Morphogens and pattern formation (chick limb bud)D. Hormones (in amphibian development)
1. pattern of metamorphosis2. role of thyroxin3. evidence
ectoderm endodermmesoderm
3. resegregation
1. dissociation
2. reaggregation
Holtfretter 1955
Fig. 47.22Spemann and Mangold: an organizer
Fig. 47.24 Pattern formation: the chick limb bud
Fig. 47.24Pattern formation: the chick limb bud
Tadpole
AquaticGillsHerbivorousSwimming
Frog
TerrestrialLungsCarnivorousJumping
metamorphosis
How do hormones turn on and off the genes that control development?
Thyroxin level (increasing w ith time)G
rou
p o
f g
enes
exp
ress
ed
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
Size of tadpole
Time
Pond dries, metamorphosis
or death
larger
smaller
Bigger is better!
20 mm 20 mm
Stage 36
O
C
Stage 27
C
O
Stage 42
O
C
Omnivore Carnivore
Omnivore Carnivore
Comparison of beaks of spadefoot tadpoles
Size of tadpole
Time
Pond dries, metamorphosis
larger
smaller
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
Adult HeterochronyNeotenyPaedomorphosis
Chemical pollutants can influence hormones and alter development
Lake Apopka
Concentration of toxins in
water
Lake Apopka
higher
lower
Lake Woodruff
Lake Apopka
larger
smaller
Lake Woodruff
Alligatorpenissize
Alligatorpenissize
Concentration of toxins in water
higherlower
larger
smaller
Effects of Atrazine on frog development