List of top Questions asked in CBSE CLASS XII

According to the 2011 census, how is urbanisation distributed across Indian states?

A child with blood group A has father with blood group B and the mother with blood group AB. Choose the option that gives the correct genotypes of father, mother, and the child:

Immunity in our body is of two types: (i) Innate immunity and (ii) acquired immunity. Innate immunity is a non-specific defence mechanism, whereas acquired immunity is pathogen-specific; it is called specific immunity too. Acquired immunity is characterised by memory. Antibodies are specific to antigens and there are different types of antibodies produced in our body: they are IgA, IgE, IgG, IgC, and IgM. It shows primary response when it encounters the pathogen for the first time and secondary response during the subsequent encounters with the same antigen/pathogen. Name the two types of specialised cells which carry out the primary and secondary immune response.

Describe ‘Ex situ’ approach for conserving biodiversity. Give any two examples.

Explain the steps of amplification of gene of interest using PCR technique.

Explain giving three reasons why tropics show greatest levels of species diversity.

The world is facing the accelerated rate of species extinctions due to human activities. Explain any three major causes of biodiversity losses.

Draw the diagram of a mature pollen grain released at the two-celled stage and label four parts in it.

Why are these animals being produced? Explain any four reasons.

What are transgenic animals?

Explain how is a bacterial cell made ’competent’ to take up recombinant DNA from the medium.

Draw a graph showing species-area relationship. Name the naturalist who studied such relationship. Write the observation made by him.

Give a schematic representation of oogenesis in human females.

Immunity in our body is of two types: (i) Innate immunity and (ii) acquired immunity. Innate immunity is a non-specific defence mechanism, whereas acquired immunity is pathogen-specific; it is called specific immunity too. Acquired immunity is characterised by memory. Antibodies are specific to antigens and there are different types of antibodies produced in our body: they are IgA, IgE, IgG, IgC, and IgM. It shows primary response when it encounters the pathogen for the first time and secondary response during the subsequent encounters with the same antigen/pathogen.

(d) How is active immunity different from passive immunity?

The process of copying the genetic information from one strand of DNA into RNA is termed as transcription. The principle of complementarity of bases governs the process of transcription, also except that uracil comes in place of thymine. Study the complete transcription unit given below and answer the following questions:

Describe the location of (C) and (D) in the transcription unit.

Mention the number of chromosomes at each stage. Correlate the life phases of the individual with the stages of the process.

Describe the three types of pollination that can occur in a chasmogamous bisexual flower.

The process of copying the genetic information from one strand of DNA into RNA is termed as transcription. The principle of complementarity of bases governs the process of transcription, also except that uracil comes in place of thymine. Study the complete transcription unit given below and answer the following questions:

Identify coding strand and template strand of DNA in the transcription unit.

The process of copying the genetic information from one strand of DNA into RNA is termed as transcription. The principle of complementarity of bases governs the process of transcription, also except that uracil comes in place of thymine. Study the complete transcription unit given below and answer the following questions:

Identify (C) and (D) in the diagram, mention their significance in the process of transcription.

The process of copying the genetic information from one strand of DNA into RNA is termed as transcription. The principle of complementarity of bases governs the process of transcription, also except that uracil comes in place of thymine. Study the complete transcription unit given below and answer the following questions:

Name the main enzyme involved in the process of transcription.

Samples of blood and urine of a sports person are collected before any sports event for drug tests. (a) Why is there a need to conduct such tests? (b) Name the drugs the authorities usually look for. (c) Write the generic names of two plants from which these drugs are obtained.

How does the process of Natural Selection affect Hardy-Weinberg equilibrium? Explain with the help of graphs.

Study the pie chart given below, representing the global biodiversity and proportionate number of species of major taxa.

Answer the following questions:
[a] Identify 'X' and 'Y' in the given pie chart.
[b] Which one of the two 'X' or 'Y' is the most species-rich taxonomic group and by what percentage?
[c] Name the level of Biodiversity represented by the following:

(i) Estuaries and alpine meadows in India.
(ii) The medicinal plant \textit{Rauwolfia vomitoria}.

Immunity in our body is of two types: (i) Innate immunity and (ii) acquired immunity. Innate immunity is a non-specific defence mechanism, whereas acquired immunity is pathogen-specific; it is called specific immunity too. Acquired immunity is characterised by memory. Antibodies are specific to antigens and there are different types of antibodies produced in our body: they are IgA, IgE, IgG, IgC, and IgM. It shows primary response when it encounters the pathogen for the first time and secondary response during the subsequent encounters with the same antigen/pathogen.

(c) The organ transplants are often rejected if not taken from suitable compatible persons. [(i)] Mention the characteristic of our immune system that is responsible for the graft rejection. [(ii)] Name the type of immune response and the cell involved in it.

An application of biotechnology in agriculture involves the production of pest-resistant plants, using "cry" gene from a bacterium, \textit{Bacillus thuringiensis.} (a) Proteins coded by which specific Bt. toxin gene control corn borer? (b) How does Bt. toxin produced by the bacterium kill the insect? Explain.