In blind cave fish, eyes do not form. However, transplantation of the lens from a closely-related aboveground fish into the optic cup of the cave fish induces eye development. What does this suggest about the loss of vision in the cave fish?
A. Primary induction of the eye fails in the cave fish because the lens lacks some critical signal.
B. Secondary induction of the eye fails in the cave fish because the lens lacks some critical signal.
C. Primary induction of the eye fails in the cave fish because the optic cup lacks the ability to receive some critical signal.
D. Secondary induction of the eye fails in the cave fish because the optic cup lacks the ability to receive some critical signal.
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 eye formation? 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?
B. Secondary induction of the eye fails in the cave fish because the lens lacks some critical signal.
Clarify Question
What is the key concept addressed by the question?
· This question is asking about the steps in the formation of the eye.
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 eye development.
Gather Content
What do you already know about eye formation? What other information is related to the question?
· Induction is a foundational mode of development in vertebrates.
· Primary induction refers to a structure that is derived directly from one of the germ layers.
· Secondary induction occurs when a tissue that is already on a set developmental path gives rise to a structure.
· Since the optic cup is present, lack of eye development must be due to the lack of a signal to the lens that would carry out secondary induction.
Choose Answer
Given what you now know, what information is most likely to produce the correct answer?
· Primary induction would not be at work here, as the eye is a structure that is derived from tissue that is already on a developmental path.
· The optic cup has formed in this fish, so developmental failure is not due to lack of this structure.
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 induction in a new situation. If you got an incorrect answer, did you remember that primary induction causes the development of a structure from the germ layers, or that secondary induction occurs when a structure develops from tissue with a set developmental path?
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