Final answer:
The three classes of bryophytes are liverworts, hornworts, and mosses. The development of a vascular system allowed plants to transport nutrients efficiently, supporting increased size and complexity, and providing structural support.
Step-by-step explanation:
Bryophyte Classification and Vascular System in Plants
The three classes of bryophytes are liverworts, hornworts, and mosses. These non-vascular plants are important in understanding plant evolution and diversity. Liverworts, or Marchantiophyta, are considered among the earliest land plants. Hornworts, or Anthocerotophyta, possess unique single-celled stomata, whereas mosses, or true Bryophyta, represent a distinct division and are considered most closely related to vascular plants among the bryophytes.
The development of a vascular system in plants was a significant evolutionary advancement. It allowed for the efficient nutrient transport within a plant's body, which supported increased complexity and size. The system consists of specialized cells that form tissues such as xylem and phloem, which transport water, minerals, and nutrients throughout the plant. These vascular tissues enable plants to grow taller and larger, as they can now move resources over greater distances, and provide structural support. As a result, plants with a vascular system can compete more successfully for light and other resources, leading to their dominance in many ecosystems.