Imagine an earthworm that has no chaetae. How would the lack of chaetae affect movement of the earthworm?

Question

A.  The earthworm would have difficulty changing locations, since it cannot anchor itself in the soil.
B.  The earthworm would be much flatter than normal since it has no hydrostatic skeleton.
C.  The earthworm would only be able to extend its body segments.
D.  The earthworm would only be able to shorten its body segments.
E.  The earthworm would not be able to move at all.

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?

Gather Content
· What do you know about the function of chaetae? 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

A.  The earthworm would have difficulty changing locations, since it cannot anchor itself in the soil.

Clarify Question
· What is the key concept addressed by the question?
        o The question asks about the function of chaetae.
· What type of thinking is required?
        o You are being asked to apply your knowledge about the function of chaetae.

Gather Content
· What do you know about the function of chaetae? What other information is related to the question?
        o On the underside of a worm’s body are short, bristlelike structures called chaetae. When circular muscles act, the chaetae of that region are pulled up close to the body and lose contact with the ground. Circular-muscle activity is passed backward, segment by segment, to create a backward wave of contraction. As this wave continues, the anterior circular muscles now relax, and the longitudinal muscles take over, thickening the front end of the worm and allowing the chaetae to protrude and regain contact with the ground. The chaetae now prevent that body section from slipping backward. This locomotion process involves waves of circular-muscle contraction  followed by waves of longitudinal-muscle effects.

Choose Answer
· Given what you now know, what information is most likely to produce the correct answer?
        o Without chaetae, the earthworm would have difficulty changing locations, since it cannot anchor itself in the soil. The chaetae are on the outside of the earthworm, while the muscles that extend and shorten body segments are inside of the earthworm.

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?
        o This question asked you to apply your knowledge about the function of chaetae. If you got the correct answer, great job! If you got an incorrect answer, where did the process break down? Did you think that the chaetae controlled muscle contractions? Did you think that chaetae regulated the skeleton?