Question

Describe two adaptations that are present in mosses, but not hornworts or liverworts, which reflect steps of evolution toward land plants.

a) Mosses have a cuticle layer and stomata, aiding in water retention and gas exchange.
b) Mosses possess vascular tissues and seeds, facilitating nutrient transport and reproduction.
c) Mosses exhibit xylem and phloem, enabling upward water movement and sugar transport.
d) Mosses have seeds enclosed in fruit, promoting seed dispersal and protection.

Answer 1

Mosses have evolved to have a protective cuticle layer and stomata for better water retention and gas exchange, which are key steps towards terrestrial adaptation, unlike other non-vascular plants such as liverworts and hornworts.

Step-by-step explanation:

While mosses, liverworts, and hornworts are all non-vascular bryophytes and share a common ancestry with green algae, mosses possess certain adaptations that reflect evolutionary steps toward land plants. Specifically, mosses exhibit a cuticle layer and stomata. The cuticle provides a protective barrier that reduces water loss, vital for survival in terrestrial environments. Stomata allow mosses to regulate gas exchange, which is crucial for photosynthesis and respiration. Though some mosses have structures that resemble vascular tissue, these are not true vascular tissues like xylem and phloem found in higher plants. Therefore, mosses lack true vascular tissues and seeds that facilitate nutrient transport and reproduction.

These adaptations are significant as they represent a shift from a fully aquatic life, as seen in green algae, to a terrestrial one. Even so, without the development of a vascular system seen in higher plants, mosses remain typically small and are commonly found in moist environments where they can absorb water directly through their leaf-like structures.