If you rub the scaled skin of a shark, it feels rough if you move your hand from tail to head but smooth if you move from head to tail. What is a major advantage of the scales being oriented this way?

Question

A.  to keep the shark afloat in the water
B.  to counteract friction as the shark swims through the water
C.  to better protect the shark from predators
D.  to better prevent water loss from the body tissues
E.  to enable the shark to orient itself in space and detect prey

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 role of friction in movement? 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.  to counteract friction as the shark swims through the water

Clarify Question
· What is the key concept addressed by the question?
        o The question asks about the role of friction in movement.
· What type of thinking is required?
        o You are being asked to apply your knowledge about the role of friction in movement to explain the orientation of scales on a shark.

Gather Content
· What do you know about the role of friction in movement? What other information is related to the question?
        o For swimming animals, the buoyancy of water reduces the effect of gravity. As a result, the primary force retarding forward movement is frictional drag, so body shape is important in reducing the force needed to push through the water. In addition to shape, the orientation of scales is important. If the scales overlap like shingles on a roof from the head to the tail, water will move over them smoothly, reducing friction. Water moving back from tail to head would encounter a rough surface producing more friction that would slow down the shark.

Choose Answer
· Given what you now know, what information is most likely to produce the correct answer?
        o The best answer is that the scales feel smooth from head to tail on the shark as that is the direction water will flow as the shark swims. This reduces friction and makes movement through the water more efficient. The orientation of the scales will not affect the rate of water loss or buoyancy. While the skin of some sharks can be used to detect prey and provide defense, there is no evidence in this question that the orientation of the scales will make a difference.

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 role of friction in movement to explain the orientation of scales on a shark. If you got the correct answer, great job! If you got an incorrect answer, where did the process break down? Did you think that buoyancy or water loss would be affected by the orientation of the shark’s scales? Did you think that the orientation of the shark’s scales would affect detection of prey or protection from predators?