In which of the following, isogamous conditions with non-flagellated gametes are found?

The correct option is D

Spirogyra

The correct option is option D

Explanation of the correct option:

1. It is a member of green algae.
2. It is a free-floating filamentous alga.
3. The plant body is a multicellular, unbranched filament.
4. Sexual reproduction is of isogamous type.
5. In isogamous reproduction, both the fusing gametes are morphologically and physiologically alike.
6. The gametes are non-flagellated(non-motile) and similar in size.

Explanation of the incorrect option:

Option A:

1. It is a member of brown algae.
2. In Fucus only the male gametes are motile in nature whereas the female gametes are non-motile in nature.

Option B:

1. It is a member of green algae.
2. The gametes are flagellated and similar in size.

Option C:

1. It is also a member of green algae.
2. The female gamete is non flagellated thus non-motile whereas the male gamete is flagellated and motile.

Final answer: In spirogyra, isogamous conditions with non-flagellated gametes are found.