What would result if too many cells left the surface of the embryo to move inside during gastruation?

Question

A.  Too little endoderm, resulting in missing gut and organs
B.  Too little ectoderm, resulting in missing nervous system or skin
C.  Problems in muscle development
D.  Too little protoderm, resulting in missing organs


Clarify Question
What is the key concept addressed by the question?

What type of thinking is required?

Gather Content
What do you already know about the fate of the surface cells? What other information is related to the question?

Choose Answer
Given what you now know, what information is most likely to produce the correct answer?

Reflect on Process
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
 

Answer 1

B.  Too little ectoderm, resulting in missing nervous system or skin


Clarify Question
What is the key concept addressed by the question?
     · This question is asking about the consequences of a deficiency of surface cells during gastrulation.

What type of thinking is required?
     · Apply level:
       o You are being asked to take what you already know and use, or apply, it to the fate of an embryo with too few surface cells.


Gather Content
What do you already know about the fate of the surface cells? What other information is related to the question?
     · Gastrulation creates the three primary germ layers: endoderm, ectoderm, and mesoderm.
     · The cells in each germ layer have very different developmental fates.
     · The cells that move into the embryo to form the tube of the primitive gut are endoderm; they give rise to the lining of the gut and its derivatives (pancreas, lungs, liver, etc.).
     · The cells that remain on the exterior are ectoderm, and their derivatives include the epidermis on the outside of the body and the nervous system.
     · The cells that move into the space between the endoderm and ectoderm are mesoderm; they eventually form the notochord, bones, blood vessels, connective tissues, muscles and internal organs such as the kidneys and gonads.

Choose Answer
Given what you now know, what information is most likely to produce the correct answer?
     · The endoderm is derived from the inside of the archenteron, so a lack of surface cells would not affect its development.
     · Muscles are derived from the mesoderm, so lack of surface cells, which would give rise to the ectoderm, would not affect muscle development.
     · Since the surface cells give rise to the ectoderm, lack of cells here could cause an issue with deficiencies in the skin or nervous system.


Reflect on Process
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
     · Apply level:
       o Answering this question correctly depended on your ability to use the germ layers in a new situation. If you got an incorrect answer, did you remember that the ectoderm is derived from the outer layer during gastrulation, or that the nervous system and skin are derived from the ectoderm?