Question

Which of the following fixes nitrogen?

• A. Anabaena
• B. Ulva
• C. Ulotrix
• D. Spirogyra

Hint:

Anabaena, a cyanobacterium, is essential for nitrogen fixation in aquatic ecosystems.

Answer 1

The Correct Option is A

Step 1: Understand nitrogen fixation.
Nitrogen fixation is the process by which nitrogen in the atmosphere is converted into ammonia or other molecules by certain microorganisms.
Step 2: Review the options.
- Anabaena is a cyanobacterium known for its ability to fix nitrogen in aquatic environments.
- Ulva, Ulotrix, and Spirogyra are algae, but they do not have nitrogen-fixing capabilities like Anabaena.
Step 3: Conclude.
Anabaena is the correct answer because it can fix nitrogen, making option (A) the correct answer.
Final Answer: \[ \boxed{\text{Anabaena}} \]