Developmental Pattern in Metazoans

Question 1

Coelom formation

Schizocoely

Answer 1

Coelom forms from splitting
* Band of mesoderm forms around the gut before a coelom forms
* Coelom is formed by mesodermal cells dividing

Question 2

Coelom formation

Enterocoely

Answer 2

Coelom forms by out pocketing
* Mesoderm and coelom form at the same time
* Invagination of blastula bending inward forming the archenteron
* Sides of the archenteron push outwards into pouch-like coelomic compartment
* Pouch-lie compartments pinch off

Question 3

Coelom body plans

Answer 3

• Acoelomate
• Pseudocoelomate
• Eucoelomate/coelomate

Question 4

Coelom body plans

Acoelomate

Answer 4

• Formed by schizocoely
• No coelom but have digestive cavity (triploblastic)

Question 5

Coelom body plans

Pseudocoelomate

Answer 5

• Formed by schizocoely
• Coelom partially lined with mesoderm

Question 6

Coelom body plans

Eucoelomate/Coelomate

Answer 6

• Formed enterocoely/schizocoely
• Coelom develops fully from mesoderm

Question 7

Mosaic development

Answer 7

• Cytoplasmic specification
• Cytoplasmic determinants not distributed evenly in blastomeres
• Individual blastomeres cannot produce whole embryo

Question 8

Regulative development

Answer 8

• Conditional specification
• Neighbouring cells induce cell fate
• Individual blastomeres can produce whole embryo

Question 9

Induction (regulative development)

Answer 9

Capacity of cells to evoke a developmental response from other cells