Lampreys completely lack parathyroid glands. Suggest why these glands may be important for other vertebrates, but not for jawless fish.

Question

A.  Because they are parasitic, lampreys get plenty of calcium from their hosts.
B.  Living in the ocean, they are surrounded by large amounts of sodium, chloride, and magnesium ions.
C.  Jawless fish employ a different system than other vertebrates to regulate blood sugar.
D.  Since they have a cartilaginous skeleton but not true bone, they have less need to regulate calcium levels.

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Answer 1

D.  Since they have a cartilaginous skeleton but not true bone, they have less need to regulate calcium levels.

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What is the key concept addressed by the question?
        · Why do lampreys not need a parathyroid gland?
What type of thinking is required?
            o This is an evaluate question because you have to consider different potential reasons why a parathyroid gland is not needed in lampreys.

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What do you already know about the parathyroid gland? What other information is related to the question?
        · The parathyroid gland releases parathyroid hormone, which increases blood calcium levels by promoting the dissolution of calcium phosphate crystals of the bone matrix, the increased absorption of calcium by the intestines, and the reabsorption of calcium by the kidneys.

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Given what you now know, what information is most likely to produce the correct answer?
        · Why would lampreys not need a parathyroid gland while other vertebrates do? The parathyroid hormone regulates calcium and a large portion of calcium is usually stored in bones. Bones are something the cartilaginous lampreys do not have, thus they have less need to regulate calcium levels as vertebrates with bones. Lampreys are parasitic on other fishes, but their teeth in their circular mouths are not designed to crunch bones of their hosts, but to bite out little pieces of muscle, so they do not get considerable amounts of calcium from feeding.

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?
        · Answering this question correctly depended upon understanding the function of the parathyroid gland and thinking about how lampreys are different from other vertebrates. If you got the answer correct, great! If not, where did you go wrong? Did you know that lampreys are parasitic and think that they received plenty of calcium from their hosts?