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 Arthropods Mollusks Annelids Protostomes Deuterostomes Acoelomates TIME

Mouth develops: First Second Cleavage planes: Spiral Radial Early development: Not totipotent Totipotent

EGG MORULA

SEA URCHIN BLASTULA

Fig 47.16

Start of invagination (blastopore) Blastocoel Fig 47.9 Animal pole 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 larger or death Size of tadpole smaller Time

Stage 36 O C Omnivore Carnivore 20 mm Stage 27 C O Stage 42 O C

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

Concentration of toxins in water higher lower Lake Woodruff Lake Apopka

Lake Apopka larger smaller Lake Woodruff Alligator penis size

Concentration of toxins in water larger Alligator penis size smaller lower higher Concentration of toxins in water

Effects of Atrazine on frog development