SAT Subject Biology Practice Question 113: Answer and Explanation

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Question: 113

3. An organism that demonstrates radial symmetry and an exoskeleton would be classified into which phylum?

A. Arthropoda
B. Cnidaria
C. Echinodermata
D. Mollusca
E. Porifera

Correct Answer: C


The phyla Mollusca and Arthropoda do not exhibit radial symmetry; they are bilaterally symmetrical. Phylum Porifera demonstrates an asymmetrical body plan. Phylum Cnidaria does exhibit radial symmetry; however, this group lacks any skeletal form, leaving the only possible correct answer to be Echinodermata.

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