**Core Concept**
The tongue is a unique organ composed of multiple embryological origins, resulting in distinct anatomical and histological features. The anterior two-thirds of the tongue is primarily derived from ectoderm, while the posterior one-third originates from endoderm. This developmental difference affects the tongue's structure, function, and innervation.

**Why the Correct Answer is Right**
The posterior one-third of the tongue is indeed derived from endoderm, not mesoderm. This region of the tongue is lined by stratified squamous epithelium, similar to the rest of the tongue, and is responsible for taste, mastication, and swallowing. The endodermal origin of the posterior tongue is crucial for its development and function. The correct developmental origin of the tongue is essential for understanding its anatomy, histology, and clinical correlations.

**Why Each Wrong Option is Incorrect**
**Option A:** This statement is true, as the entire tongue is initially derived from endoderm during embryonic development.

**Option B:** This statement is true, as the anterior two-thirds of the tongue are lined by surface ectoderm, which is responsible for the formation of the tongue's outer layer.

**Option C:** This statement is true, as the sulcus terminalis marks the junction between the ectodermal and endodermal regions of the tongue.

**Option D:** This statement is incorrect, as the posterior one-third of the tongue is actually derived from endoderm, not mesoderm.

**Clinical Pearl / High-Yield Fact**
The tongue's unique embryological origins should be remembered using the mnemonic "E-E-E" - Ectoderm (anterior two-thirds), Endoderm (posterior one-third), and Epithelial lining (common to both regions). This mnemonic helps in recalling the developmental origins of the tongue and its clinical implications.

✓ Correct Answer: D. Posterior 1/3rd - Mesodermal