Abstract
<jats:p>The olfactory organ of vertebrates represents one of the most ancient sensory systems, preserving essential functions throughout evolution. Chemical signal perception underlies food acquisition, predator avoidance, territorial and reproductive behavior, and orientation. During the transition from aquatic to terrestrial environments, profound structural and functional changes occurred within the olfactory apparatus, resulting in the diversification of nasal cavities and the emergence of specialized sensory regions. In jawless vertebrates and fish, the olfactory organ functions as a chemosensory monitor of dissolved substances; in early tetrapods, the differentiation of nasal passages and secondary palates enabled the perception of airborne odorants. Amphibians exhibit both main and vomeronasal olfactory organs, reflecting adaptation to dual habitats. Reptiles exhibit further specialization through the development of nasal turbinates and a functionally distinct vomeronasal system, which is involved in social and territorial communication. In birds, olfactory capacity is highly variable, ranging from partial reduction in visually oriented taxa to remarkable enlargement in species relying on chemical navigation. Mammals display the highest degree of morphological and functional complexity: extended nasal cavities with intricate turbinals, a pseudostratified olfactory epithelium containing Bowman’s glands, and well-developed main and accessory olfactory bulbs. Comparative studies reveal conserved developmental and molecular mechanisms, including the “one receptor–one neuron–one glomerulus” principle across vertebrate classes. Analysis of olfactory evolution demonstrates that, despite ecological diversification and partial regressions, the structural plan of the vertebrate olfactory system remains remarkably conservative, providing a model of how ancient sensory architectures adapt to new environmental and behavioral demands.</jats:p>