Question

Life cycle in Chlamydomonas / Ulothrix / Spirogyra is
A) Diplontic
B) Diplohaplontic
C) Haplontic
D) None of the above

Answer 1

In biology, a life cycle is the sequence of changes that members of a species go through as they progress from the start of one developmental stage to the start of the same developmental stage in the next generation.

Complete answer:
Based on the number of haploid and diploid generations, algae have five distinct types of life cycles.
1. Haplontic life cycle
2. Diplontic life cycle
3. Haplodiplontic life cycle
4. Haplobiontic life cycle
5. Haplo-diplobiontic life cycle
Option A) Diplontic – is an incorrect answer because during diplontic life cycle meiosis occurs in gametes, and the dominant and independent phase is the diploid sporophyte. A gametophyte is a haploid organism of haploid gametes.
Option B) Diplohaplontic – is an incorrect answer because mitosis occurs in both diploid and haploid cells in haplodiplontic. Bryophytes go through a gametophyte stage before moving on to the sporophytic stage. They are multicellular and mostly live on their own. Sporic meiosis, on the other hand, has two mitosis events in each process (diplobiontic).
Option C) Haplontic - is the correct answer because the dominant phase of the haplontic life cycle is haploid, and the diploid phase is short, that is, when the zygote is produced by the fusion of two haploid cells.
Option D) None of the above - is an incorrect answer as haplontic is the correct answer.
Hence, the Life cycle in Chlamydomonas , Ulothrix , Spirogyra is haplontic.

Note:
Starting with a diploid zygote or spore and finishing with a fully mature alga plant, all algae go through a haploid life cycle of growth. Algae are divided into three classes: Chlorophyceae, Phaeophyceae, and Rhodophyceae.