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Why must ectoderm lie near dorsal mesoderm before it can develop into neural tissue?

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embryos of different animals — Animal development The embryos of many animals appear similar to one another in the earliest stages of development and progress into their specialized forms in later stages.

In vertebrate animal development, ectoderm must be positioned near dorsal mesoderm to undergo neural differentiation because of a process known as embryonic induction.

At the start of gastrulation, ectoderm is incapable of progressive development on its own. It requires the influence of the underlying dorsal mesoderm—which eventually forms the notochord and somites—to trigger its transformation into the neural plate. This induction occurs through the emission of diffusible substances from the mesodermal cells, which act upon the overlying ectoderm to direct its developmental path. Without this specific interaction, the ectoderm would not acquire the ability to differentiate into neural tissue, as the mesoderm acts as a primary organizer that dictates the fate of the surrounding embryonic layers.1