The symbiotic nitrogen-fixing cyanobacterium in Azolla is: MCQ with Answer and Explanation

The symbiotic nitrogen-fixing cyanobacterium in Azolla is:
A. Spirulina
B. Nostoc
C. Anabaena azollae
D. Oscillatoria
Answer: Option C
Solution (By JKExamLibrary)
Anabaena azollae lives in cavities of the water fern Azolla and fixes atmospheric nitrogen. It is used as a biofertilizer in rice paddies.

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Practice More Biology Questions

Question #1
The bone that protects the brain is the:
A. Vertebra
B. Sternum
C. Cranium
D. Pelvis

Correct Answer: Option C


Explanation:
The cranium (skull) is composed of several bones fused together, encasing and protecting the brain. Vertebrae protect the spinal cord, sternum protects the heart and lungs anteriorly, pelvis supports abdominal organs and connects to legs. The cranium also provides attachment for muscles.

This question belongs to: Science Biology
Question #2
The end product of glycolysis under anaerobic conditions in muscles is:
A. Carbon dioxide
B. Lactic acid
C. Acetyl CoA
D. Ethanol

Correct Answer: Option B


Explanation:
When oxygen is limiting, pyruvate from glycolysis is reduced to lactic acid (lactate) by lactate dehydrogenase, regenerating NAD⁺ to allow glycolysis to continue. In yeast, pyruvate is converted to ethanol and CO₂ (alcoholic fermentation). Muscle cells lack alcohol dehydrogenase.

This question belongs to: Science Biology
Question #3
The structure that carries urine from the kidney to the bladder is the:
A. Ureter
B. Urethra
C. Renal pelvis
D. Calyx

Correct Answer: Option A


Explanation:
The ureters are two muscular tubes that propel urine from the renal pelvis of each kidney to the urinary bladder via peristaltic contractions. Urethra exits bladder, renal pelvis and calyces are within the kidney.

This question belongs to: Science Biology