[Campbell Biology P.1099] Based on the provided Key and developmental diagrams for triploblas... | Practice Question

Based on the provided Key and developmental diagrams for triploblasts, which of the following best describes the general location of the mesoderm when it is present during and after development?

  • A: The mesoderm is primarily found forming the outermost layer, covering the embryo's surface.
  • B: The mesoderm is consistently located as the innermost lining of the primitive gut.
  • C: The mesoderm is situated between the ectoderm and the endoderm.
  • D: The mesoderm is formed only in diploblasts and is responsible for the gastrovascular cavity.

Explanation

The Key indicates that mesoderm is represented by red, ectoderm by blue, and endoderm by yellow. In the triploblast diagrams Planaria and Sea urchin , the red mesoderm layer is consistently depicted as forming between the blue ectoderm outer layer and the yellow endoderm inner lining of the gut , fulfilling its role as an intermediate germ layer.