List of top Biology Questions asked in CBSE CLASS XII

(a) (i) Name the group of drugs whose skeletal molecule is shown below:
\begin{figure}[h!] \centering \includegraphics[width=0.5\linewidth]{Screenshot 20250115 143511.png} % Replace with the correct path to your image \caption{Drug} \label{Drug} \end{figure}

(ii) How are such drugs consumed?

(b) State the basis of ‘ABO’ blood grouping in humans.

(b) Name the (i) apelike (ii) manlike primates that existed 1.5 million years ago.

(a) Whose skulls ‘A’, ‘B’, and ‘C’ are shown below? Which of the two are more similar to each other?
\begin{figure}[h!] \centering \includegraphics[width=0.5\linewidth]{Screenshot 20250115 143253.png} % Replace with the correct path to your image \caption{skull} \label{Skull} \end{figure}

(a) Name the source from which insulin was extracted in earlier times. Why is this insulin no more in use by the diabetic patients?
Answer:
Source: Pancreas of pigs and cows. Reason: Animal insulin caused allergic reactions in some patients due to structural differences from human insulin. (b) Why does the insulin synthesized in the human body undergo processing whereas the insulin produced by Eli Lilly company does not need to undergo any processing? Explain.

(b) Name any two hotspots in India.

Study the graph given below that represents the changes in the thickening of the uterine wall in women ‘X’ and women ‘Y’ over a period of one month:
\begin{figure}[h!] \centering \includegraphics[width=0.5\linewidth]{Screenshot 20250115 143034.png} % Replace with the correct path to your image \caption{Graph} \label{Graph} \end{figure} What does the graph with respect to women ‘X’ and women ‘Y’ indicate? Give a suitable reason.

(a) Intensely lactating mothers generally do not conceive. Why?
Answer:
Lactational amenorrhea prevents ovulation during intense lactation. Prolactin, the hormone responsible for milk production, suppresses gonadotropin release. (b) Why has our government intentionally imposed strict conditions for MTP (Medical Termination of Pregnancy)?

Assertion (A): Some aquatic ecosystems have inverted biomass pyramids.
Reason (R): More energy is required by organisms occupying higher trophic levels.

(b) Explain Brood parasitism with the help of a suitable example.

(a) Differentiate between grazing food chain and detritus food chain.

(a) Biodiversity hotspots cover less than 2\% of Earth’s land area. Strict protection of these areas can reduce the rate of ongoing extinctions. Explain.

The ‘molecular scissors’ fall in the category of:

Assertion (A): Patents are granted by governments to an inventor.
Reason (R): Patents prevent others from commercial use of an invention.

Assertion (A): Plasmids are autonomously replicating circular extrachromosomal DNA.
Reason (R): Plasmids are usually present in eukaryotic cells.

Assertion (A): A given fig species can be pollinated only by its partner wasp.
Reason (R): The wasp pollinates the fig inflorescence while searching for suitable egglaying sites.

ELISA technique is based on the principle of:

Who proposed the mutation theory in favour of organic evolution?

Which of the options has correct identification of ‘P’, ‘Q’ and ‘R’ in the illustration of ‘Central Dogma’ given below?

Which was the last of the 24 human chromosomes to be completely sequenced?

Study the following diagram of Transverse Section of a young anther of an angiosperm:

Identify the category of genetic disorder depicted in the pedigree chart given below:

Turner’s syndrome in humans occurs due to: