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If you are the student who reads beyond the NCERT box on the nephron, the biology olympiad is built for you. It rewards reasoning about experiments and data rather than recall, and it starts with a single two-hour paper in your own city. This post explains the stages, how the first paper is marked, how students are chosen for the next round, and how to start preparing, using HBCSE's official information for 2026-27.
How is the biology olympiad organised?
The Homi Bhabha Centre for Science Education (HBCSE, part of TIFR) is the nodal centre for India's olympiads. Its Science Olympiad 2026-2027 page and the 2026-27 brochure describe a five-stage process:
NSEB, the National Standard Examination in Biology, run by the Indian Association of Physics Teachers (IAPT) with teacher associations.
INBO, the Indian National Biology Olympiad, run by HBCSE.
OCSC, an orientation-cum-selection camp at HBCSE, with theory and practical tests.
Pre-departure training for the selected team.
The International Biology Olympiad (IBO), with a team of four.
The brochure says India has taken part in biology since 2000, and that the first two stages "do not necessarily require any specialised coaching outside the regular school system".
Who can take NSEB?
For the 2026-27 cycle, the brochure's main criteria are: eligible to hold an Indian passport; born between 1 July 2007 and 30 June 2012; studying in Class X, XI or XII when enrolling; and not finishing Class XII before 30 November 2026. Students taking NSEJS that year cannot also take NSEB. Enrolment, through a registered school centre or directly on the IAPT website, cost Rs 300 per subject and ran from 21 August to 14 September 2026. Read the full list in the brochure, since the age window moves each year.
How is NSEB marked?
The brochure lists NSEB 2026 on Sunday, 22 November 2026, 2:30 to 4:30 pm, in English, Hindi and several other languages. It has two parts:
Part A: 48 multiple-choice questions with one correct answer. +3 for correct, −1 for wrong.
Part B: 12 questions with one or more correct options, 6 marks each. You get credit only if you mark all the correct options and no wrong one.
So the maximum is 48 × 3 + 12 × 6 = 144 + 72 = 216.
Example. A student gets 30 right and 10 wrong in Part A, and 5 fully right in Part B. Score = 30 × 3 − 10 + 5 × 6 = 90 − 10 + 30 = 110.
How are students selected for INBO?
The brochure splits NSEB candidates into Group A (Class XII on 30 November 2026) and Group B (Class XI or X). For each group it sets a target of at least 200 students for INBO, and applies these rules:
Minimum Admissible Score (MAS): 50% of the average of the top ten scores, rounded down. No one below it qualifies.
Merit Index (MI): 80% of that average, rounded down. Anyone at or above it qualifies automatically.
A state and UT quota, a top-up to reach the target, and a supernumerary rule so that at least 20% of those selected are female, all subject to MAS.
Example. If the top ten scores in your group average 160, MAS = 80 and MI = 128. A score of 110 clears MAS, so whether you go through depends on your state's quota and your rank.
INBO 2027 is listed for 31 January 2027. About 40 students go from INBO to the biology OCSC, 20 from each group, and the IBO team of four is chosen from the camp.
How should you prepare?
HBCSE's syllabus page says NSEB and INBO are "broadly equivalent to the senior secondary level" of CBSE up to Class 12, but that the questions are "usually non-conventional and of high difficulty level". That combination suggests a plan:
Know NCERT Class 11 and 12 biology well, including figures and experiments. This is your base.
Practise reading data. Olympiad questions often give a graph, a table or an experiment and ask what follows. For every chapter, find one experiment and ask what result would disprove the idea.
Use past papers. HBCSE's past papers page has INBO papers with model solutions going back to 2009.
Keep physics and chemistry going. Biophysics, biochemistry and quantitative questions appear, and the syllabus expects mathematics up to Class 12.
When a past-paper question turns on a concept you have only memorised, the Fermi Concept Library covers every concept in biology, chemistry and physics with its own lesson, so you can fill that gap before the next paper. If you are weighing other subjects too, read our guides to the physics olympiad and the chemistry olympiad.
This weekend, download one INBO paper from the HBCSE site and try its first five questions without a time limit.
