Sponges and ctenophores have both been proposed as basal metazoans. Which of the

Question

Sponges and ctenophores have both been proposed as basal metazoans. Which of the following types of data support the idea that sponges are the basal group?

A.structure of collar cells, bilateral symmetry of larvae, sequences of cadherin genes, and molecular clock

B.fossil steroids, molecular clock, lack of tissues in sponges, and structure of collar cells

C.sequences of collagen genes, bilateral symmetry of adults, cleavage type, and fossil steroids

D.sequences of cadherin genes, cleavage type, structure of collar cells, and bilateral symmetry of adults

A.structure of collar cells, bilateral symmetry of larvae, sequences of cadherin genes, and molecular clock

B.fossil steroids, molecular clock, lack of tissues in sponges, and structure of collar cells

C.sequences of collagen genes, bilateral symmetry of adults, cleavage type, and fossil steroids

D.sequences of cadherin genes, cleavage type, structure of collar cells, and bilateral symmetry of adults

Explanation / Answer

Answer is B. fossil steroids, molecular clock, lack of tissues in sponges, and structure of collar cells.

Because there is no bilateral symmetrical strucure on spnoge and they lack tissues and organs. The surface contains conical or cylyndrical collar cells. Molecular clock gives idea that sponges existed well before Cambrian explosion.

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