Question

The first division of zygote is a reduction division in
a. Algae
b. Bryophyta
c. Pteridophyta
d. All of the above

Answer 1

In meiosis, first cell division is the reduction division. In reduction division, chromosome number is reduced to half i.e. from diploid to haploid. By this process, germ cells are produced. It is also known as the first meiotic division.

Complete answer:
In algae, haploid life cycle is commonly found. There are both haploid and diploid stages present in the life cycle of algae, and these two stages are separated by meiosis and syngamy. The zygote is diploid (2n). Then the zygote undergoes first meiotic division (reduction division) to form a haploid (n) spore. The end result of meiosis is the formation of four spores. The spores then undergo mitosis division to become mature.

The matured organism can either undergo asexual reproduction to produce identical offspring, or it can follow sexual reproduction cycle and produce gametes through mitosis. Through syngamy, the gametes fuse together, this process is also known as fertilization. Fused gametes then form a zygote again which are diploid (2n) and the whole process is repeated again where zygote undergoes first meiotic division to produce spore.

Hence, the correct answer is option (A).

Additional information:
In the haploid life cycle, the gametophytic phase is dominant. The photosynthetic phase is dominant, which is gametophyte (free-living). Thus, it is known as haplontic life cycle. Algae such as Volvox, Chlamydomonas, and Spirogyra show haplontic life cycle.

Note: In bryophyta and pteridophyta, haplo-diplontic life cycle is present in which both haploid and diploid phases are present. In bryophyte, the gametophytic phase is dominant but a short-lived sporophytic phase is also present. In pteridophyta, sporophytic phase is dominant but a short-lived gametophytic phase is also present.