NEET UG · Biology · Mineral Nutrition

Nitrogen Fixation: NEET previous year questions

This topic’s chapter, Mineral Nutrition, is not in the NEET UG 2026 syllabus. It had 6 questions from 2017 to 2025; they are kept here for reference.

Asked in 10 years: 6; about 0.6 per paper
Years asked: 6/10; last asked 2025
Syllabus: Dropped; not in NEET UG 2026
Last asked: 2025; 1 papers ago

Key findings

01
Asked in 6 of 10 papers, 6 questions in all: #141 of 204 topics by ten-year total. It comes back every 1.6 years on average. Last asked in 2025.
02
80% of its questions since 2018 tested an idea never asked before; none repeated an idea from the year before.
03
The most repeated idea is Non-Legume Symbiotic Fixation, asked 2 times (2017, 2022), usually as “identify symbiont for a host plant”.
04
NEET has asked 5 of the 86 ideas in this topic; 78 have never been asked, directly or indirectly.
05
Mostly asked as one-line MCQ (67%); 50% easy, 0% hard, and down from 0.7 to 0.3 questions a paper since 2024.

Questions per year

Up to 2023: 0.7; per paper
Since 2024: 0.3; -0.4
Usual gap: 1.6 yrs; between papers asking it
Swing: ±0.5; questions, year to year

How it is asked

Difficulty, format and skill

Across all 6 questions on Nitrogen Fixation since 2017.

Difficulty

QUESTIONS

Easy3 · 50%
Medium3 · 50%
Hard0 · 0%

Format

One-line MCQ · 4 Q67%
Other · 1 Q17%
Match the lists · 1 Q17%

Skill tested

Recall · 5 Q83%
Application · 1 Q17%

Repeats

New idea, or one asked before?

Each column is a paper. Blue questions tested an idea NEET had not asked before; navy ones went back to an idea from an earlier paper. 2017 is the first paper, so everything in it counts as new.

’17’18’19’20’21’22’23’24’25’26

Idea asked for the first time
Idea asked in an earlier paper

Coverage of the topic

NEET has asked 5 of the 86 ideas in this topic. 78 have never been asked yet.

Asked directly5 · 6%
Touched inside another question3 · 3%
Never asked78 · 91%

Ideas come from Lumi’s syllabus map of NCERT. A never-asked idea is not a safe skip: most new questions come from exactly these.

Drill down

Idea, year, question

Every idea NEET tested in this topic, with its ten papers. Open one to read the questions.

ideaAskedShareYears’17’18’19’20’21’22’23’24’25’26

Repeated2 · 33%33%2/10
- 2022 · Q131
  Which one of the following produces nitrogen fixing nodules on the roots of Alnus ?
  easyOne-line MCQ
- 2017 · Q93
  Select the mismatch :
  mediumOne-line MCQNew idea
1 · 17%17%1/10
1 · 17%17%1/10
1 · 17%17%1/10
1 · 17%17%1/10

Squares are the ten papers, 2017 to 2026; darker means more questions. Share is of the level above.

Ideas

Every idea inside this topic

5 different ideas were tested; 1 came more than once. Nitrification: Ammonia to Nitrite is the foundation for 2 other ideas in the syllabus.

Non-Legume Symbiotic Fixation2×
identify symbiont for a host plant
One-line MCQ · 4% next
Cyanobacterial N2 Fixers1×
odd-one-out among organisms
Other · 4% next
Nitrification: Ammonia to Nitrite1×
match list on nitrogen cycle bacteria
Match the lists · 4% next · foundation for 2
Nitrogenase Reaction Byproducts1×
identify products of enzyme reaction
One-line MCQ · 4% next
Denitrifying Bacteria1×
identify process by bacterial genus
One-line MCQ · 4% next · foundation for 1

Idea	Times	Format	Chance next	Foundation for
Non-Legume Symbiotic Fixationidentify symbiont for a host plant	2	One-line MCQRecall	4%	–
Cyanobacterial N2 Fixersodd-one-out among organisms	1	OtherApplication	4%	–
Nitrification: Ammonia to Nitritematch list on nitrogen cycle bacteria	1	Match the listsRecall	4%	2 ideas
Nitrogenase Reaction Byproductsidentify products of enzyme reaction	1	One-line MCQRecall	4%	–
Denitrifying Bacteriaidentify process by bacterial genus	1	One-line MCQRecall	4%	1 ideas

Chance next is the historical rate at which an idea with this record came back in the following paper. It is low for every idea, which is why learning the topic beats memorising past questions. All repeated ideas

Every question

Nitrogen Fixation questions, year by year

The opening words of each question as it appeared in the official paper, with the idea it tested.

NEET 20251 question

Q113
Which of following organisms *cannot* fix nitrogen? A. *Azotobacter* B. *Oscillatoria* C. *Anabaena* D. *Volvox* E. *Nostoc* Choose the…
Idea: Cyanobacterial N2 Fixers
New ideaEasyOther

NEET 20221 question

Q131
Which one of the following produces nitrogen fixing nodules on the roots of Alnus ?
Idea: Non-Legume Symbiotic Fixation
EasyOne-line MCQ

NEET 20211 question

Q140
Match Column - I with Column - II. Column - I | Column - II (a) Nitrococcus | (i) Denitrification (b) Rhizobium | (ii) Conversion of…
Idea: Nitrification: Ammonia to Nitrite
New ideaEasyMatch the lists

NEET 20201 question

Q13
The product(s) of reaction catalyzed by nitrogenase in root nodules of leguminous plants is/are :
Idea: Nitrogenase Reaction Byproducts
New ideaMediumOne-line MCQ

NEET 20191 question

Q131
Thiobacillus is a group of bacteria helpful in carrying out :
Idea: Denitrifying Bacteria
New ideaMediumOne-line MCQ

NEET 20171 question

Q93
Select the mismatch :
Idea: Non-Legume Symbiotic Fixation
MediumOne-line MCQ

Questions from the official NEET UG papers published by NTA (CBSE before 2019). Topic and idea tags, counts and notes are Lumi’s.