Why do adult urochordates (tunicates) lack notochords, even though larval urochordates have them? Larvae use notochords to _____
A) aid in swimming; adults are sessile and thus no longer propel themselves.
B) stiffen their bodies; in adults, the notochord is replaced by a column of bone.
C) induce tissue differentiation; in adults, tissue is already differentiated.
D) organize their nervous systems; adults' nervous systems are fully developed and do not change.
Answer: A
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