Important Topics of Biology for IISER Entrance Exam 2025; Check Topics and Subject Weightage
Indian Institutes of Science Education and Research Entrance Exam 2025 ( IISER Entrance Exam )
IISER Exam 2025 Biology sections comprise 15 questions and exam officials test candidates' domain knowledge and analytical understanding of the Class 11 and 12 Biology syllabus. Check out this Shiksha article to know the IISER exam 2025 important topics of biology to ace the exam with an extra score.
Biology Important Topics For IISER Entrance Exam
The Indian Institutes of Science Education and Research (IISER) offer one of the most prestigious science education programs in India. The IISER Aptitude Test (IAT) is conducted annually for admission into the BS-MS dual degree programs. Among the four subjects tested—Physics, Chemistry, Mathematics, and Biology—many aspirants find Biology either their strongest or weakest link. Considering the high competition level of the examination, a strategic IISER Biology Preparation must be done by the test takers.
If you are targeting IISER through the IAT 2025, it is crucial to understand the important topics in Biology, their weightage, and how to effectively prepare. This article will serve as a detailed guide to help you master Biology for the IISER exam.
- IISER Entrance Exam Overview and Biology Weightage
- Most Important Topics in Biology for IAT 2025
- IAT 2025: Biology Topic-Wise Weightage
- IISER Entrance Exam 2025: Preparation Strategy for Biology
- Last-Minute Tips for Biology in IAT 2025
- How to Attempt the Biology Section in Exam
IISER Entrance Exam Overview and Biology Weightage
The IISER Entrance Exam consists of 60 multiple-choice questions, 15 from each subject. The paper is divided equally among the four core subjects:
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Biology – 15 Questions
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Physics – 15 Questions
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Chemistry – 15 Questions
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Mathematics – 15 Questions
Each question carries 3 marks, and 1 mark is deducted for incorrect answers. Hence, a good performance in Biology can significantly boost your overall score.
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Also Read: IISER Biology Syllabus 2025 (OUT): Check Class 11 and Class 12 NCERT Biology Syllabus Here
Most Important Topics in Biology for IAT 2025
Rules related to withdrawal/refund of Seat Acceptance Fee (SAF):
1. The application fee paid during filling up the application form is not refundable.
2. Refund policy for the Seat Acceptance Fee (SAF) is given below:
- The candidate can withdraw his/her seat by selecting the option “WITHDRAW SEAT” in the application portal. No other form/method of withdrawal is accepted. Email or phone communication in this regard shall not be entertained.
- Once a candidate has withdrawn, he/she will not be considered for further rounds of counseling/admission process. A withdrawn candidate cannot re-enter the admission process under any circumstances.
There are two important withdrawal dates:
? Round-wise withdrawal (RW) date, and
? Final withdrawal (FW) date. RW and FW dates can be found below. - If a candidate withdraws from the counselling process before RW deadline, then no cancellation fee will be applicable, i.e., the entire SAF (after the deduction of bank charges, if applicable) will be refunded.
- If a candidate withdraws after the RW deadline, but before the FW deadline, then a non-refundable administrative fee will be deducted which is ?10,000/- (Rupees ten thousand only) for GEN/OBC/OBC-NCL/EWS/PwD/KM and Kashmiri Pandit/Kashmiri Hindu Families (non-migrants) candidate and ?5,000/- (Rupees five thousand only) for SC/ST candidates.
- Once a candidate has withdrawn the seat through the counselling portal, the amount due will be refunded to the bank account provided in the IISER Preference Form. Such candidates do not need to take any additional steps towards their SAF refund. All efforts will be made to ensure that the refunds are processed within 15 working days after the withdrawal.
- The Seat Acceptance Fee will be eventually transferred to the IISER which the candidate finally registers at, and the respective IISER will adjust the fees that may be applicable, locally from the candidate upon registration at the particular IISER. Any withdrawal after the FW deadline will be taken care by that particular IISER following the instructions given below.
- If the candidate fails to join in-person at the offered IISER on the joining date mentioned in the offer letter of the respective IISER, the cancellation fee decided by the concerned IISER will be applicable.
- Further, a candidate who has paid the SAF but fails to show up by the last date of admission fee payment at the concerned IISER, will not be considered for further rounds of admission.
- If the candidate decides to discontinue after joining any particular IISER, the refund policy of that IISER will be applicable.
IISERs and JAC are not liable for losses incurred if an application is not withdrawn in the above manner on or before the stipulated date and time.
Once IISER result is declared, a seat allotment list is declared containing roll numbers of candidates who are allocated seats in BSMS programme through different channels (SCB, KVPY JEE). Candidates can check the first round allotment list on the official website of the exam on July 15, 2025, Tentatively. All candidates whose roll numbers appear in the first round allotment list need to log in to their application portal to download the offer letters.
With an emphasis on both conceptual understanding and application-based learning, the biology section evaluates a student's grasp over core topics such as cell biology, genetics, ecology, physiology, evolution, and biotechnology. These areas not only form the foundation of modern biological sciences but are also pivotal in solving real-world challenges in health, agriculture, and the environment. A strategic focus on these key topics can significantly enhance a candidate's performance, making it essential to understand their relevance and interconnectedness.
Cell Structure and Function:
Key Concepts:
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Cell theory
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Prokaryotic vs eukaryotic cells
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Cell organelles: structure and function
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Biomolecules
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Cell division: Mitosis and Meiosis
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Why it's important: This chapter is heavily conceptual and frequently tested. Questions often revolve around organelle functions and phases of cell division.
Tip: Focus on diagrams and differences (e.g., between prokaryotic and eukaryotic cells, or mitosis vs meiosis).
Genetics and Evolution:
Key Concepts:
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Mendel’s laws of inheritance
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Dihybrid and monohybrid crosses
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Sex determination
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DNA structure, replication, and transcription
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Genetic disorders
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Evolutionary theories
Why it's important: This is a high-yield topic. IAT frequently includes tricky questions involving Punnett squares or pedigree charts.
Tip: Practice lots of genetics problems. Understanding inheritance patterns and calculations is essential.
Human Physiology:
In case candidates wish to reset the password, candidates will have to follow the steps given below:
Visit the IISER 2025 website
Click on the Log in tab
Click on 'Reset/Change Password' tab
A link will be mailed to the registered email id
Click on the link and change/reset the password
The portal for document upload and freezing of IISER preferences for IISER 2025 Admissions can be done in the window period in the month of July 2025, tentatively. After accepting the offer and paying seat acceptance fee, the candidate can exercise two options:
- Candidate can FREEZE the seat (they will not participate in further rounds of counselling),
- Candidate can FLOAT (they will participate in further rounds of counselling to get their higher preferences). The FLOAT option is activated by default for those who pay the seat acceptance fee. A student who has chosen to FLOAT will be again considered for seat allocation in the next round. If they are eligible to secure a seat in an IISER that is higher in their preference list than the currently accepted one, they will be offered that seat.
The following items or objects will not be allowed to be carried to the IISER 2025 exam centres.
- Stationery items such as test-based material (written/printed), papers, notes, Pencil box, pouches, geometry box, pen, scale/ruler, eraser, etc.
- Electronic devices such as calculators, cameras, electronic pens, scanners, etc.
- Accessories such as bags, belts, caps, goggles, wallets, etc.
- Devices used for communication such as mobile phones, smart watches, Bluetooth, fitness bands, earphones, pager, etc.
- Eatables (packed or home-cooked), thermos, etc.
Key Concepts:
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Digestive system
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Respiratory system
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Circulatory system
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Excretory system
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Nervous and muscular system
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Endocrine glands
Why it's important: At least 2–3 questions are expected from this section. Diagrams and function-based questions are common.
Tip: Use flowcharts and summary tables to remember hormone actions and feedback mechanisms.
Plant Physiology:
Key Concepts:
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Photosynthesis
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Respiration in plants
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Transport in plants
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Plant hormones
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Growth and development
Why it's important: This area is rich in conceptual understanding and processes. Numerical and factual questions based on diagrams and reactions are common.
Tip: Focus on light and dark reactions, and functions of plant hormones (like auxins, gibberellins, etc.).
Ecology and Environment:
Key Concepts:
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Ecosystems
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Biodiversity and conservation
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Environmental issues
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Organisms and populations
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Biogeochemical cycles
Why it's important: This is often considered easier and scoring. Questions are usually direct and based on facts.
Tip: Focus on understanding the food chains, ecological pyramids, and biogeochemical cycles.
Reproduction:
Key Concepts:
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Reproduction in organisms
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Sexual reproduction in flowering plants
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Human reproductive system
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Reproductive health
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Gametogenesis and fertilization
Why it's important: Diagrams, hormonal control, and stages of development are frequently asked.
Tip: Understand the menstrual cycle, gametogenesis, and male/female reproductive structures clearly.
Biotechnology and Its Applications:
Key Concepts:
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Principles of biotechnology
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Genetic engineering (rDNA technology)
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Applications in health and agriculture
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Genetically Modified Organisms (GMOs)
Why it's important: This is a modern and application-based topic. It can have 1–2 questions in IAT.
Tip: Focus on the steps in gene cloning, use of restriction enzymes, and practical applications like Bt cotton.
Also Read:
| IISER Physics Syllabus | IISER Mathematics Syllabus |
| IISER Biology Syllabus | IISER Chemistry Syllabus |
IAT 2025: Biology Topic-Wise Weightage
Based on analysis of past papers and trends:
| Topic | Approximate Weightage |
|---|---|
| Cell Structure & Function | 2–3 Questions |
| Genetics and Evolution | 2–3 Questions |
| Human Physiology | 2–3 Questions |
| Plant Physiology | 1–2 Questions |
| Ecology and Environment | 1–2 Questions |
| Reproduction | 1–2 Questions |
| Biotechnology | 1 Question |
| Diversity & Classification | 1 Question |
IISER Entrance Exam 2025: Preparation Strategy for Biology
1. Follow NCERT Thoroughly
Most IAT Biology questions are directly or indirectly based on NCERT. Do not skip:
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Line-by-line reading
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Diagrams and tables
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NCERT summary boxes
2. Practice with PYQs
Solving IISER previous year question papers (PYQs) helps you understand the type of questions and difficulty level.
3. Make Topic-Wise Notes
Summarize each chapter with:
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Key terms
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Diagrams
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Important points
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Mnemonics for classification or steps
4. Revise Regularly
Biology involves a lot of memorization. Use spaced repetition techniques and flashcards for regular revision.
5. Take Mock Tests
Simulate the exam environment with full-length IAT mock tests. Analyze your performance in the Biology section to identify weak areas.
6. Recommended Resources
Books:
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NCERT Class 11 & 12 Biology – Primary resource
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Trueman’s Elementary Biology Vol I & II – For deeper understanding
- MTG Objective NCERT at Your Fingertips (Biology) – For practice questions
Also Read: IISER Entrance Exam 2025 Books: Check Best Books for Exam Preparation
Last-Minute Tips for Biology in IAT 2025
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Quickly revise key concepts and flowcharts
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Focus on high-yield topics like Genetics, Cell Biology, and Human Physiology
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Solve 2–3 mock papers weekly in the last month
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Stay updated with any syllabus changes from the official IISER site
How to Attempt the Biology Section in Exam
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Start with direct questions like Ecology or Reproduction to gain confidence
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Mark doubtful questions for review and come back later
-
Avoid guesswork—each incorrect answer reduces your net score
-
Use elimination to improve your odds on tricky MCQs
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Student Forum
Anything you would want to ask experts?Answered 2 months ago
With a 7,000 rank in the SC category, admission to any IISER (including newer campuses) is not possible as per 2025 cutoffs. Cutoff ranks for SC category in IISERs generally close between 125 (most competitive) and 750 (least competitive).
P
Contributor-Level 7
Answered 2 months ago
IISER Berhampur cutoff 2025 for the BS + MS course across multiple specialisations stood at 3299 during the Round 1 cutoff for the students belonging to the General AI quota. So, considering the first-round cutoff rank, candidates must target to secure a rank up to 3299 and lower to improve their ch
R
Contributor-Level 10
Answered 2 months ago
IISER Mohali cutoff 2025 has been released for different categories of students under the AI quota. For the General category, the cutoff rank for BS + MS admission across multiple specialisations was 1778. To view the category-wise ranks, refer to the table below:
| Category | BS + MS |
|---|---|
| General | 1778 |
| OBC | 1358 |
| SC | 520 |
| ST | 263 |
| EWS | 480 |
| PWD | 50112 |
R
Contributor-Level 10
IISER Entrance Exam Notifications
No. Students are not permitted to carry any electronic device including a calculator. However, candidates need not to get worried about the calculator as the numerical which will be asked in the examination will be upto the class 12. Candidates need to remember some basic log values which can be used in solving some of the equations in mathematics and Physics The student will be provided with plain sheets to do their calculation.