In what way are a human and a crab similar?

Question

A.  Vertebrates and arthropods are deuterostomes.
B.  Both have muscles that pull against rigid skeletons.
C.  Both have closed circulatory systems.
D.  Both have a continuous growth pattern.

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 crustaceans?

Choose Answer
· Given what you now know, what information and/or problem solving approach 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.  Both have muscles that pull against rigid skeletons.

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses crustaceans.
· What type of thinking is required?
        o This question is asking you to take what you already know and apply it to this unfamiliar situation.

Gather Content
· What do you already know about crustaceans?
        o A crab is a crustacean, which is a member of the arthropods, part of the Ecdysozoa.
        o Like other arthropods, crabs molt periodically, they have an open circulatory system, and they have an external rigid skeleton called the exoskeleton.

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Are both vertebrates and arthropods deuterostomes? No. There are a few invertebrates that are deuterostomes, but arthropods like a crab are protostomes.
        o Do both vertebrates and arthropods have closed circulatory systems? No. Vertebrates have a closed circulatory system, arthropods have an open circulatory system.
        o Do both vertebrates and arthropods have a continuous growth pattern? No. Vertebrates do, but arthropods growth in steps at each molt.
        o Do both vertebrates and arthropods have muscles that pull against rigid skeletons? Yes! In vertebrates, muscles pull against a rigid endoskeleton of bone; in arthropods, muscles pull against a rigid exoskeleton of chitin.

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 The question required you to take what you already know and apply it to this unfamiliar situation.
        o Did you recognize that arthropods like a crab also use muscles against a rigid skeleton? Their skeleton, however, is on the outside – an exoskeleton.