The plant kingdom is traditionally classified into five major groups based on increasing structural complexity and reproductive specialization: Algae, Bryophytes, Pteridophytes, Gymnosperms, and Angiosperms.

This progression reflects key evolutionary milestones: the move from aquatic to terrestrial habitats, the development of vascular tissue, and the evolution of seeds.

• ›Algae and Bryophytes lack true vascular tissue (xylem/phloem); Pteridophytes, Gymnosperms, and Angiosperms all possess vascular tissue, classifying them together as vascular plants (Tracheophytes)
• ›Recognizing WHERE vascular tissue and seeds each first appear is essential for understanding the evolutionary narrative this chapter builds toward