CSIR NET Life Science Unit-Wise Weightage and Important Topics

To find the real unit-wise weightage in CSIR NET Life Science, we studied 2,593 questions from 19 papers held between 2018 and 2025. We sorted every question into the 14 units of the new Life Sciences and Bio-Technology (LS-BT) syllabus. Here is what the papers show:

• Unit 10 (Ecology and Behavioral Biology) gave the most questions in both Part B and Part C. It was about 1 in 8 questions.
• Four units gave about 41% of Part C: Unit 10, Unit 1 (Biomolecules), Unit 8 (Inheritance Biology) and Unit 9 (Evolution and Diversity).
• Every other life science unit gave between 6.5% and 9%. So no unit is safe to skip.
• The three biotechnology units (11, 12 and 13) gave under 5% together. These units are new to most CSIR NET students, and the new LS-BT paper may ask more from them.
• No single topic was big. The most common topic gave only 3.2% of Part C.
• Part A tested the same three skills again and again. 353 of its 375 questions came from numerical ability, reasoning and data interpretation.

So plan your preparation by unit. Start with the units that come most often, and study every topic inside them, because the questions are spread widely. Practice Part A every week.

Below are the unit-wise and subject-wise numbers, the most frequent topics, one real Part C question, and a study plan built from the data.

Which CSIR NET papers did we analyse?

We used 19 papers: June 2018, December 2018, June 2019, both shifts of November 2020, February 2022, September 2022, June 2023, December 2023, June 2024 and December 2024, and the single papers of June 2025 and December 2025.

A note on the numbers: about 6% of the questions in these papers are not counted here. Some had a problem in the question or its answer key, and some are still being checked. All percentages are worked out from the questions we counted.

These numbers describe past papers. They can help you decide what to study first. They cannot tell you exactly what the next paper will ask.

CSIR NET Life Science unit-wise weightage (Part B and Part C)

The units below are from the new 14-unit LS-BT syllabus.

Three things stand out:

• Unit 10 leads both parts. Community ecology, biodiversity and conservation, population ecology and ecosystem ecology all came often. Behaviour questions add to this unit too.
• Eleven units sit close together. Units 1 to 10 and Unit 14 each gave between 7% and 13.4% of Part C. The gap between them is small, so every one of them needs proper study.
• The order is almost the same in Part B and Part C. When you prepare a unit well for Part C, you also prepare it for Part B.

CSIR NET Life Science subject-wise weightage

Many books and coaching notes are still arranged by subject. Here is the same data by subject.

The same ten subjects gave about 82% of both parts. Ecology came first in Part C. Molecular Biology came first in Part B, with 104 of 924 questions.

The other subjects gave about 18% together: Immunology, Plant Diversity, RDT & Tissue Culture, Cell Signalling, Microbiology, Animal Diversity & Systematics, and a few questions from Bioprocess, Bioinformatics, physics and chemistry.

CSIR NET Life Science important topics (Part B and Part C)

These are the topics that came most often. Revise them first and come back to them often.

Most frequent topics in Part C

Ranks 9 to 11 are tied at 24 questions each.

Most frequent topics in Part B

Ranks 6 to 12 are tied at 16 questions each.

Proteins came first in Part C, and Biodiversity & Conservation came first in Part B. Four of the eleven Part C topics are from Unit 10.

Is studying only the important topics enough?

No. Inside each unit, the questions are spread over many topics. Even the top topics above gave only about a quarter of each part: 25.3% of Part C and 24.9% of Part B. The single most common topic gave just 3.2% of Part C, and we found 144 different topics in Part B alone.

So if you study only a list of top topics, about three-quarters of the paper is still left. Use the topic lists to decide what to revise first and most often. Then cover the other topics of each unit too.

Example: a real Part C question from December 2025

Here is a question from Unit 1 in the December 2025 paper:

Given below are statements on the citric acid cycle and urea cycle, which have shared metabolic intermediates:

A. Oxaloacetate is converted to aspartate. B. Fumarate is a citric acid cycle intermediate. C. Arginosuccinate is cleaved to fumarate and arginine. D. Aspartate combines with citrulline to produce argininosuccinate in the mitochondrial matrix.

Which one of the following options represents the combination of all correct statements?

(1) A and D only (2) B and C only (3) A, C and D (4) A, B and C

Answer: (4) A, B and C.

Statements A, B and C are correct. Statement D gets the place wrong. Aspartate and citrulline combine in the cytosol. The statement puts this step in the mitochondrial matrix, so it is false.

Look at what the question needs. It joins two pathways, the citric acid cycle and the urea cycle. You need both, and you need to know where each step happens. A student who studied only one "important topic" in metabolism could lose this question. This is why the plan below asks you to cover whole units.

CSIR NET Part A (General Aptitude): what comes most often?

The subtopics that came most often:

1. Mensuration & Basic Geometry: 58 questions
2. Number System & Basic Arithmetic: 54
3. Logical Reasoning (deductive and inductive): 46
4. Line Graphs & Trend Analysis: 27
5. Spatial Reasoning & Visual Aptitude: 23

Part A questions look different from paper to paper. But most of them test these same skills. Speed comes from regular practice, so do a little Part A work every week.

How to prepare for CSIR NET Life Science using this weightage

Step 1: Put the units in three groups

Notice one thing. Group 2 gives more questions in total than Group 1. Each unit in it is a little smaller, but there are seven of them. So Group 1 comes first in your order, and Group 2 needs just as much care.

Step 2: Study each unit in this order

1. Order your units by group. Adjust for your own background (see the section after next).
2. Start every topic with its past questions. I did this when I prepared for GATE and IIT JAM in 2020–21. Attempt the topic's PYQs first. The ones you cannot solve show you what to read. Then read, and attempt them again.
3. Revise the frequent topics first and most often. Use the two topic lists above.
4. Practice Part A a few times every week. Start with mensuration, number system and logical reasoning.
5. Take mixed tests across units. Part C questions often join two topics, like the example above. Mixed tests train you to see which concepts a question is really testing.

Will the weightage change in the LS-BT paper from December 2026?

From December 2026, the Life Sciences paper of the Joint CSIR-UGC NET becomes Life Sciences and Bio-Technology (LS-BT), and DBT's JRF fellowships are now awarded through it. The official notice from CSIR-HRDG says the paper will have enough optional questions from both Life Sciences and Biotechnology. The new 14-unit syllabus adds three biotechnology units: Bioinformatics and Computational Biology (Unit 11), Biochemical Engineering and Industrial Biotechnology (Unit 12), and Advances in Biotechnology (Unit 13). Dates, fees and eligibility for the first LS-BT exam are in our CSIR NET December 2026 notification article.

Our numbers come from papers before this change. In those papers, Units 11, 12 and 13 gave under 5% of Part C together. The LS-BT paper may give these units much more space, so the share of the other units could fall. We do not know yet by how much.

The December 2026 exam keeps the same Part A, B and C pattern. Check csirnet.nta.nic.in for any update before your exam. Use these numbers to set your study order, and update the plan when the first LS-BT papers come out.

When should you change this study order?

• You are strong in a unit from your degree. Revise it quickly with PYQs and give the saved time to a weaker unit.
• You are weak in a Group 1 unit. Start it first, because it carries the most questions.
• You come from a biotechnology background. Units 11 to 13 may now suit you. Keep them in your plan, and still cover Group 1 well.
• You have little time left. Focus on Group 1 and Part A first, then the frequent topics of Group 2.
• A unit came less often in the past. It can still come in your paper. Use frequency to set the order of study. Every unit on the syllabus can still come.