Question

Which of the following group of plants shows the dominant phase of haploid gametophyte generation?
I. Angiosperms
II. Gymnosperms
III. Horsetails, ferns, club mosses (lycophytes and pteridophytes)
IV. True mosses, liverworts, and hornworts (bryophytes)

A. I only
B. I and II
C. I, II, and III
D. III and IV
E. IV only

Answer 1

In cases of bryophytes the dominant generation is haploid. In pteridophytes both diploid and haploid generations are dominant.

Complete answer:
Alternation of Generation is a type of life cycle that happens on those algae and plants that have specific haploid sexual and diploid asexual stages in the heterokontophyta and archaeplastida. A haploid multicellular gametophyte that carries n chromosomes alternates with a diploid multicellular sporophyte that carries 2n chromosomes. A mature sporophyte generates haploid spores by meiosis, a mechanism that decreases the number of chromosomes become n from 2n.
Plants go through both haploid as well as diploid generations during their life cycle. This is termed as alternation of generations. The sporophyte that develops spores by meiosis is the diploid plant structure. These spores form a gametophyte that is haploid, which gives rise to the haploid gametes. However, the dominant generation varies between plants when alternation of generation occurs. Although in case of bryophytes (mosses and liverworts) the dominant generation is haploid, the diploid generation is dominant in the tracheophytes (vascular plants), and the sporophyte makes up the principal plant. So, we can say that true mosses, liverworts, and hornworts (bryophytes) show the dominant phase of haploid gametophyte generation.

Thus, the correct answer is option E. i.e., IV only.

Note: Alteration of the generations is described as the change in the life cycle of the organism of multicellular diploid and haploid forms. The generation of gametophytes starts with a meiosis produced spore. The spore is haploid, and all the resulting cells are haploid (by mitosis). In time, this multicellular structure causes mitosis, and then the generation of diploid sporophytes is created by sexual reproduction. The generation of sporophytes therefore begins with a zygote. The diploid number of chromosomes is included in their cells. However, some cells will eventually go through meiosis, spores will develop and a new generation of gametophytes will start.