Question

Meiosis in Ulothrix takes place during
A. Zoospore formation
B. Gamete formation
C. Zygote formation
D. Zoospore germination

Answer 1

Hint:- Algae are chlorophyll-bearing, simple, thalloid, autotrophic and largely aquatic organisms. They occur in different habitats: moist stones, soils and wood. They may be colonial or filamentous. Based on structure, algae are thalloid that is plant body isn't differentiated into root, stem and leaves. Based on nutrition, algae are photoautotrophic. They have photosynthetic pigments.

Complete Answer:- Reproduction in algae takes place by various methods such as as- vegetative reproduction, asexual reproduction and sexual reproduction. Vegetative reproduction occurs by fragmentation during which filaments break down into small pieces and form new filaments.Asexual spores like zoospores are formed in favourable conditions and other spores like aplanospores, hypnospores and akinetes are formed during unfavourable conditions. These spores on germination (zoospore germination) produce new plants asexually.
In algae, sexual reproduction takes place through gamete formation. Algae are classified into three classes named as- Chlorophyceae, Phaeophyceae and Rhodophyceae. Sexual reproduction in algae is of three types- isogamous, anisogamous and oogamous. The fusion of similar or comparable sized gametes is called as isogamy while the fusion of dissimilar sized gametes is called as anisogamy.
Ulothrix is classified under the class Chlorophyceae. It is filamentous algae normally reproduce through vegetative reproduction. But during sexual reproduction, gametes are formed which can be isogamous, anisogamous or oogamous. Their fusion results in formation of zygotes. Germination of the zygote by meiotic division leads to the formation of characteristic sexual spores.

In Ulothrix, meiotic division takes place through zygote formation. Thus the correct answer is option (C).

Note:- In Chlorophyceae (green algae), sexual reproduction may be of isogamous, anisogamous or oogamous type. In these algae, various varieties of sex cells are formed during sexual reproduction. Some commonly found chlorophyte algae are: Chlamydomonas, Volvox, Ulothrix, Spirogyra and Chara.
In Phaeophyceae (brown algae), sexual reproduction may be of isogamous, anisogamous or oogamous type. In these algae, the union of gametes may occur in water or within the oogonium (oogamous species). Their gametes are pyriform (pear-shaped) and bear two laterally attached flagella. The commonly found brown algae are Ectocarpus, Dictyota, Laminaria, Sargassum and Fucus.
In Rhodophyceae (red algae), sexual reproduction is of oogamous type. It is completed by a complex post fertilisation development. Some commonly found red algae are Polysiphonia, Porphyra, Gracilaria and Gelidium.