[Campbell Biology P.1100] Referring to the "Late Gastrula" cross-section in Figure 47.10 and ... | Practice Question

Referring to the "Late Gastrula" cross-section in Figure 47.10 and its key, what germ layer is represented by the innermost yellow-colored structure, and what internal cavity develops from the archenteron?

  • A: Ectoderm; no internal cavity
  • B: Mesoderm; blastocoel
  • C: Endoderm; archenteron becomes the gut cavity
  • D: Endoderm; blastocoel remnant

Explanation

The key in Figure 47.10 shows that yellow represents 'Future endoderm'. In the 'Late Gastrula' cross-section, the innermost yellow-colored structure clearly corresponds to the endoderm, which lines the archenteron. The text states that 'an archenteron forms and grows' step 2 and that 'the endoderm is the innermost layer' step 3 , with the archenteron eventually forming the primitive gut cavity.