The diploid sporophyte stage is dominant in the life cycles of all of the following except
a. A pine tree.
b. A rose bush.
c. A fern.
d. A moss.

Verified step by step guidance

1. Understand the concept of alternation of generations: In plants, the life cycle alternates between a diploid sporophyte stage and a haploid gametophyte stage. The dominance of either stage varies among plant groups.
2. Recall that in most vascular plants, such as pine trees, rose bushes, and ferns, the diploid sporophyte stage is dominant. This means the sporophyte is the larger, more visible, and longer-lived stage of the life cycle.
3. Recognize that mosses are nonvascular plants, and in their life cycle, the haploid gametophyte stage is dominant. The gametophyte is the green, photosynthetic structure that is most visible in mosses.
4. Compare the life cycles of the given plants: Pine trees, rose bushes, and ferns are vascular plants with dominant sporophyte stages, while mosses are nonvascular plants with dominant gametophyte stages.
5. Conclude that the correct answer is moss, as it is the exception where the diploid sporophyte stage is not dominant in its life cycle.

Key Concepts

Sporophyte and Gametophyte Stages

In the life cycles of plants, the sporophyte is the diploid stage that produces spores through meiosis, while the gametophyte is the haploid stage that produces gametes. In most vascular plants, including pines and roses, the sporophyte is the dominant stage, whereas in non-vascular plants like mosses, the gametophyte is more prominent.

Dominance of Sporophyte in Plant Groups

Different plant groups exhibit varying dominance of the sporophyte or gametophyte stages. In angiosperms (like roses) and gymnosperms (like pines), the sporophyte is the main form, while in bryophytes (like mosses), the gametophyte is the dominant form, highlighting the evolutionary adaptations of these groups.

Examples of Plant Life Cycles

Understanding specific examples of plant life cycles helps clarify the dominance of sporophyte or gametophyte stages. For instance, ferns have a prominent sporophyte stage, while mosses primarily exhibit a gametophyte stage, which is crucial for answering questions about plant classification and life cycle characteristics.