A moss differs from a fern in having:

Question

Accepted Answer

The correct option is 1: A dependent sporophyte

The most fundamental distinction between a moss (a bryophyte) and a fern (a pteridophyte) lies in the dominance and nutritional relationship of their respective life cycle phases, specifically the sporophyte. In mosses, the multicellular diploid sporophyte, which produces spores, is non-photosynthetic or only partially photosynthetic, short-lived, and permanently remains physically attached to and nutritionally dependent on the dominant, free-living, photosynthetic haploid gametophyte plant. This dependency is a key primitive trait of bryophytes. Conversely, in ferns, the sporophyte is the dominant generation, forming the large, familiar fern plant, and it is completely independent, long-lived, and photosynthetic. The fern sporophyte develops vascular tissue (xylem and phloem) and roots, allowing it to live autonomously. The moss having a sporophyte that is dependent on the gametophyte is thus the correct feature that clearly differentiates it from a fern, where the sporophyte is independent.

The incorrect option is 2: An independent gametophyte

While a moss has a very prominent, independent gametophyte, the fern also possesses an independent, free-living gametophyte stage, known as the prothallus. The prothallus of a fern is small, heart-shaped, and usually short-lived, but it is a distinct, photosynthetic, and independent organism. Because both mosses and ferns have a free-living gametophyte, this characteristic does not serve to distinguish a moss from a fern. This trait is common among all non-seed plants (Bryophytes and Pteridophytes).

The incorrect option is 3: Alternation of generations

All plants, including mosses, ferns, and all higher plant groups, exhibit a life cycle known as alternation of generations. This refers to the cyclic presence of a haploid, gamete-producing phase (the gametophyte) and a diploid, spore-producing phase (the sporophyte). Since this is a defining characteristic of the entire Kingdom Plantae (excluding some algae), it cannot be used to differentiate mosses from ferns. The difference lies in which of these generations is dominant (gametophyte in mosses, sporophyte in ferns), not whether the alternation occurs at all.

The incorrect option is 4: Motile male gametes

Both mosses and ferns produce male gametes (sperm) that are motile, meaning they possess flagella and require a layer of external water to swim and reach the female gamete (egg). This shared requirement for water for fertilization is why both groups are typically restricted to moist or humid habitats. Since the presence of motile male gametes is common to both mosses and ferns (as well as some other lower plants), it is not a feature that distinguishes the two.