Question

which of the following are the only plants in which both the sporophyte and the gametophyte are photosynthetic and free living?

gymnosperms
nonvascular plants
angiosperms
seedless vascular plants

Explanation:

Analyze the life cycle requirements

The question asks for the group of plants where both the sporophyte and the gametophyte generations are photosynthetic and free-living. This means neither generation is nutritionally dependent on the other at maturity, and both can produce their own food via photosynthesis.

Evaluate nonvascular plants

In nonvascular plants (bryophytes like mosses), the gametophyte is the dominant, photosynthetic, and free-living generation. The sporophyte is typically small, non-photosynthetic or minimally photosynthetic, and remains permanently attached to and nutritionally dependent on the maternal gametophyte. Thus, they do not meet the criteria.

Evaluate seed plants

In seed plants (gymnosperms and angiosperms), the sporophyte is the dominant, photosynthetic, and free-living generation. The gametophyte is microscopic, non-photosynthetic (except for some early stages in gymnosperms, but still not free-living), and entirely dependent on the surrounding sporophyte tissue for nutrition and protection. Thus, they do not meet the criteria.

Evaluate seedless vascular plants

In Seedless Vascular Plants (such as ferns, clubmosses, and horsetails), there is an alternation of generations where both stages are independent. The diploid sporophyte is the large, dominant, photosynthetic, and free-living plant we commonly recognize (e.g., a fern frond). The haploid gametophyte (prothallus) is a small, heart-shaped, photosynthetic structure that grows independently on the moist soil surface. Since both generations are photosynthetic and free-living, this group perfectly matches the criteria.

Connect to mastered concepts

Using the Plant Life Cycles and Sporophyte and Gametophyte knowledge points, we can confirm that seedless vascular plants represent the unique evolutionary transition where both generations have independent, photosynthetic, and free-living existences.

Answer:

• Gymnosperms
• Nonvascular plants
• Angiosperms
• Seedless vascular plants (Correct answer)