6. Developmental Patterns and Metazoa

Question 1

Method of Coelom Formation

Answer 1

Schizocoely

Enterocoely

Question 2

Schizocoely

Answer 2

Coelom forms by splitting

• Mesoderm forms between endoderm and ectoderm
• Mesoderm cells dividing leads to coelom formation

Question 3

Enterocoely

Answer 3

Coelom forms by outpocketing

• Endoderm forms a pocket on side
• Pocket forms a bag as it separates
• No stage of only mesoderm

Question 4

Acoelomate

Answer 4

Mesoderm fills blastocoel

Question 5

Pseudocoelomate

Answer 5

Mesoderm lines one side of blastocoel

- Coelom=blastocoel (sort of)

Question 6

Coelomate

Answer 6

Mesoderm surrounds gut and splits open

- Blastocoel gone - Replaced by coelom

Question 7

Development options of Schizocoely and Enterocoely

Answer 7

Schizocoely
- Acoelomate, Pseudocoelomate, Coelomate

Enterocoely
- Coelomate only

Question 8

Cytoplasmic Specification

Answer 8

Cytoplasmic determinants signal development

• Partitioned unequally during cleavage
• Mosaic Development

Question 9

Mosaic Development

Answer 9

Each cells have a developmental faith and the collection of the cells (organs) form an organism

• Cytoplasmic Specification
• Defective structures when separated - Because it develops into only the assigned parts

Question 10

Conditional Specification

Answer 10

Cell fate not fixed until it receives positional information from neighboring cells.

• Inducer and Responder
• Regulative development

Question 11

Induction

Answer 11

Capacity of some cells to evoke a developmental response from other cells

Question 12

Inducer / Responder

Answer 12

Inducer cells induce development in responder cells

Question 13

Regulative Development

Answer 13

Inducing effect leads development

• When cell removed, neighbors can compensate for the missing part
• Conditional Specification