List of top Biology Questions asked in CBSE CLASS XII

(ii) Compare the two types of flowers with reference to:
(1) Characteristic feature
(2) Modes of pollination

(ii) Explain the genetic basis that results in the expression of this disorder.

(iii) List any two ‘out breeding devices’ in flowering plants. Explain why do plants develop such devices.

Describe the following:
(a) Describe the life cycle of HIV from the time of its entry into the human body till full blown AIDS sets in.

(iii) Work out a cross to explain how normal parents may have a sicklecell anaemic child.

(a) The given diagram shows the sectional view of a seminiferous tubule of Human testis.
\begin{figure}[h!] \centering \includegraphics[width=0.5\linewidth]{Screenshot 20250115 143912.png} % Replace with the correct path to your image \caption{Testis} \label{Testis} \end{figure} (i) Name and describe the process depicted in the diagram which results in the development of spermatozoa.

(b). Observe the picture of Commelina plant bearing two types of flowers:
\begin{figure}[h!] \centering \includegraphics[width=0.5\linewidth]{Screenshot 20250115 144128.png} % Replace with the correct path to your image \caption{Commelina} \label{Commelina} \end{figure} (i) Identify the two types of flowers labelled ‘A’ and ‘B’ in the picture.

Read the following passage and answer the questions that follow: Passage: Generally, in eukaryotic cells the average length of a transcription unit along a DNA molecule is about 8,000 nucleotides, so the RNA product of the transcription is also that long. But it only takes about 1200 nucleotides from the above RNA product to translate average sized polypeptide of 400 Amino acids. (a) Name this RNA product transcribed from the DNA that subsequently translates into a polypeptide of 400 amino acids. Mention the enzyme responsible for transcribing this type of RNA from the DNA.

(c) Write the number of RNA polymerases involved in the transcription of DNA in a prokaryote and eukaryotes.

(c) Mention the difference in the site of transcription in a prokaryote and eukaryote cell.

Populations evolve to maximise their reproductive fitness in the habitat in which they live. Study the population growth curves shown in the given graph and answer the questions that follow: \begin{figure}[h!] \centering \includegraphics[width=0.5\linewidth]{image.png} % Replace with the correct path to your image \caption{Population Growth Curves} \label{fig:populationgrowth} \end{figure} (a) Identify the growth curves \u2018A\u2019 and \u2018B\u2019.

Study the steps shown below, that are carried during a specific technique:
\begin{figure}[h!] \centering \includegraphics[width=0.5\linewidth]{Screenshot 20250115 143650.png} % Replace with the correct path to your image \caption{Steps} \label{Steps} \end{figure} (a) Identify the steps ‘A’ and ‘D’ in the diagram.

Explain the role of transgenic animals in: (a) Production of Biological Products

Explain the role of the following during the sewage treatment:
(a) Flocs
(b) Anaerobic sludge digester

(b) Draw a schematic diagram of an antibody molecule and label any 4 parts. Mention their chemical nature. Name the cells which produce them.

(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) A man with blood group ‘A’ marries a woman with blood group ‘AB’. The first child born to them has blood group ‘B’. Work out a cross to find the genotype of the father. Give the possible blood groups and their genotypes of the children that could be born to this couple. (Use a Punnet square).

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