List of top Questions asked in CBSE CLASS XII

Name and explain the property present in normal cells but lost in cancer cells.

Stability, as one of the properties of genetic material, was very evident in one of the very early experiments in genetics. Name the scientist and describe his experiment. State the conclusion he arrived at.

Draw a labelled diagram of a three-celled male gametophyte.

Explain the development of male gametophyte in an angiosperm.

Study the diagram given below that shows the steps involved in the procedure of selecting transformed bacteria and answer the questions that follow: 

 (a) Identify the colony that has got transformed. Justify your answer. 
 

Read the following passage and answer the questions that follow. 
Isn’t it incredible that India’s land area is only 2.4 percent of the world’s total land area whereas its share of the global species diversity is an impressive 8-1 percent! However, in these estimates of species, prokaryotes do not figure anywhere. Biologists are always keen on collecting data with respect to species diversity observed in different regions of the world. The data collected based on the survey conducted for species richness of groups of mammals in three different regions of the world is shown in the bar graph below.


Why is the species richness maximum in Region III in the bar graph? 
 

Describe co-evolution with the help of this example.

Explain how it is ensured that the orchid \(\textit{Ophrys is pollinated by a specific species of bee.} \)
 

With the help of an illustration only, show the action of EcoRI on a DNA polynucleotide.

Explain the convention for naming EcoRI.

Name the first transgenic cow and state its importance.

What are transgenic animals?

In a family, the father, the daughter, and the son are colour blind, whereas the mother has normal vision. Do you think the son and daughter have inherited the disease from their father? Work out a cross to justify your answer.

Identify A, B, C, D, E, and F in the table given below: 

How does meteorite analysis favour this hypothesis?

Explain the significance of the experiment carried out by S.L. Miller. Name the scientists whose hypothesis prompted him to carry out this experiment.

Mention any two applications of this technique.

Name and write two characteristics of the type of DNA that forms the basis of DNA fingerprinting technique.

Explain the mode of action of contraceptive pills taken by human females. Mention the schedule to be followed for an effective outcome.

Study the diagram of a pyramid of biomass given below. Name the two standing crops that could be occupying level ‘A’ and level ‘B’ in it. Name this type of pyramid and the ecosystem in which it is found.
\begin{center} \begin{tabular}{|c|c|} \hline Level & Description
\hline A & PC (Primary Consumer)
\hline B & PP (Primary Producer)
\hline \end{tabular} \end{center}

Why do organic farmers not recommend complete eradication of insect pests? Explain giving reason.

A farmer while working on his farm was bitten by a poisonous snake. He was rushed to a nearby health centre where the doctor gave him an injection to save his life.
(i) What did the doctor inject and why?
(ii) Name the kind of immunity provided by this injection.

Write the basic steps followed in the Assisted Reproductive Technologies (ART) programme to help childless couples. Why is it also known as test tube baby programme?

Observe the picture given below. Name the naturalist and write the explanation given by him that evolution of life forms had occurred on the basis of this example.
% Diagram placeholder \begin{center} \includegraphics[scale=0.8]{Q18.png} \end{center}