Question

Which one of the following shows isogamy with non-flagellated gametes?

• A. Ectocarpus
• B. Ulothrix
• C. Sargassum
• D. Spirogyra

Answer 1

The correct option is D

Spirogyra

The correct option is D.

Explanation for correct option:

1. Spirogyra is an unbranched filamentous green alga, a freshwater form which forms floating mass.
2. Sexual reproduction in spirogyra is known as conjugation, it involves the fusion of two morphologically identical, but physiological dissimilar gametes.
3. Isogamy involves the fusion of gametes that are morphological and physiological is similar.
4. They are called isogametes and they are non flagellated.

Explanation for incorrect options:

Option A:

1. Ectocarpus is also a flagellated brown algae that acts as a model organism, reproducing both sexually and asexually.
2. It is done through the formation of haploid or diploid biflagellate zoospores with anisogamy.

Option B:

1. Ulothrix is a non-branching flagellated green algae.
2. Ulothrix reproduces sexually via fragmentation and asexually via conjugation.

Option C:

1. Sargassum is a species of brown algae in the Phaeophyceae family, which contains seaweed, free-floating in shallow water, and coral.
2. Sexual reproduction is oogamous in this case and lacks isogamy.

Final answer: Spirogyra shows isogamy with non-flagellated gametes.