Focus on NCERT bio book’s first 3 units

  • Savita Sharma, Hindustan Times, New Delhi
  • Updated: Jan 13, 2015 17:45 IST

As we enter the last two months before the Class 12 Boards, it is time to consolidate all your efforts in various subjects. For science students, biology is a ­crucial and scoring subject. There are 16 chapters which are divided in five units. The first unit on reproduction is for 14 marks, unit 2 on genetics and evolution is for 18 marks, unit 3 called biology in human welfare is for 14 marks, unit 4 - ­biotechnology is for 10 marks and unit 5 - ecology is for 14 marks.

December and January are important when it comes to being thorough with your concepts. Read each and every line of your NCERT book. While preparing for your exam, go unit wise. Prepare all the chapters of a unit together as they are related. Start with unit 1. It has many concepts which form the basis for the chapters of other units. Chapter I of this unit talks about some very important concepts. Chapters 2 and 3 of this unit are more important than chapter 1 and 4. Spermatogenesis, oogenesis, hormonal control of the male and female reproductive systems, menstrual cycle, microsporogenesis, megasporogenesis, double fertilization, triple fusion and apomixis, methods of birth control are some of the very important topics of this unit.

Unit 2 carries the maximum weightage. All the three chapters of this unit are important. In the first chapter on principles and processes of inheritance, revise both the laws of inheritance and how to explain them with the help of monohybrid and dihybrid cross thoroughly. Incomplete dominance, pleiotropy, thalassemia autosomal and sex-linked diseases are other important topics of this chapter. In molecular basis of inheritance various experiments like Griffith’s experiment, Hershey Chase experiments, Meselson and Stahl’s experiment and their diagrams, transcription, translation, Operon Concept are very important. In fact, this entire chapter is important so prepare it thoroughly.

From evolution, in addition to origin of life (including Miller and Urey experiment) lay special emphasis on natural selection, Hardy–Weinberg principle and adaptive radiation.

Unit 4 is related to Unit 2 so after Unit 2, revise Unit 4. There are just two chapters in this unit but both are very important. Process of DNA technology, role of restriction endonucleases, plasmids, cloning vectors, RNA interference, Bt toxin, Humulin and gene therapy are some of the important topics of this unit.

In Unit 3 innate and acquired immunity active and passive immunity, T and B lymphocytes, humoral and cell mediated immunity, cancer, AIDS are important topics.

You should also be very thorough about hybrid varieties of plants and animals and diseases they are resistant to. In ecology, S and J shaped population growth, interactions among organisms, productivity, succession, ­ecological pyramids, sewage treatment, biomagnifications, eutrophication and pollution are some important topics.

Once you have revised your syllabus then use the month of February for question-based revision. Try solving previous years’ question papers. This will give you an idea of the kind of questions asked in the paper and will also let you know how to solve the paper within a few hours. Writing the answer is an art which you should master. While writing an answer, be specific and stay to the point. While attempting questions with higher weightage try writing your answer point wise. Underline all the important words and points. Presentation is very important.

(The author is HOD-biology, Studymate and can be reached at

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