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CBSE Class 12 Biology Board Exam 2020: Important diagrams from which questions are expected

Mayank Uttam

Important diagrams for CBSE Class 12 Biology Board Exam 2020 are available here. Questions based on diagrams (given in Class 12 Biology NCERT textbooks) have been frequently asked in board exams, every year. This year, CBSE Class 12 Biology Board Exam 2020 is scheduled to be held on 14th March 2020

If you will go through latest Class 12 Biology Sample Paper (issued by CBSE), then you will find many questions given in this paper are based on diagram and graphs given in NCERT textbooks.

CBSE Class 12 Biology Board Exam 2020: Some Sample Questions

Question: Draw the diagram of microsporangium of an Angiosperm and label any four parts. State the function of its innermost wall layer.

Question:  Given below is the diagram of agarose gel kept under UV light:

(a) Mention the positive and negative terminals.

(b) What is the charge carried by DNA molecule and how does it help in its separation?

(c) How are the separated DNA fragments finally isolated?

Question: The graph given below shows the distribution of biomes:

(a) What do the ‘X’ and ‘Y’ axis represent?

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(b) Identify the ‘grassland’ and ‘coniferous forest’ biomes, from the above figure.

(c) Why is ‘F’ located at the given position in the graph?

(3 Marks)


Given below is the diagram of a human ovum surrounded by a few sperms. Observe the diagram and answer the following questions:

(a) Compare the fate of sperms shown in the diagram.

(b) What is the role of zona pellucid in this process?

(c) Analyze the changes occurring in the ovum during the process.

(d) How is the entry of sperm into the ovum facilitated?

(e) Specify the region of female reproductive system where the event represented in the diagram takes place.


The graph given below shows the variation in the levels of ovarian hormones during various phases of menstrual cycle:

(a) Identify ‘A’ and ‘B’.

(b) Specify the source of the hormone marked in the diagram.

(c) Reason out why A peaks before B.

(d) Compare the role of A and B.

(e) Under which condition will the level of B continue to remain high on the 28th day?

A major portion of CBSE Class 12 Biology 2020 board exam’ question paper will be related diagrams given in Class 12 Biology NCERT textbooks. So, we have gone through previous years’ papers of CBSE Class 12

Considering the importance of diagrams in, here, we have mentioned some important topics from Class 12 Biology NCERT textbooks from which questions are expected in CBSE Class 12 Biology Board Exam 2020:

Diagrammatic representation of L.S. of a Flower

T.S. of an ovary

Anatropous ovule

Fertilisation of ovum

Schematic structure of a transcription unit

Simplified model of carbon cycle in the biosphere

Diagrammatic representation of the experimental steps in cloning and expressing a human gene (say the gene for growth hormone) into a bacterium like E. coli

Structure of some seeds

Growth of pollen tube into pistil

Deoxyribonucleic acid (DNA)


Structure of antibody

Seminiferous tubule

Primary endosperm nucleus (PEN)

Replication fork

Mendelian Dihybrid Cross

Carbon Cycle in Biosphere

Diagrammatic representation of Miller’s experiment

Sectional view of ovary

Diagrammatic representation of the mature embryo sac

Transport of ovum, fertilisation and passage of growing embryo through fallopian tube

Stages in the life cycle of Plasmodium

Diagrammatic representation of primary succession

Stages in embryo development in a dicot

Diagrammatic sectional view of female pelvis showing reproductive system

L.S. of pistil showing path of pollen tube growth


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