CBSE(NCERT) GRADE 12 BIOLOGY 2023 SET1

Which one of the following processes results in the production of recombinants in future generations?

Identify the region, process of transcription in prokaryote as shown in the schematic representation given below. Region Factor Y Enzyme Z

The status of the human population reflected in the human age pyramid given below is:

The graph plotted below is based on the data collected by biology students with respect to the levels of oxygen at the specific points in the river flowing outside their city. Which point in the graph indicates the entry of untreated sewage in the river ?

Given below are two columns. In Column I is the list of four enzymes and in Column II is the list of functions of the given enzymes. Which one of the following options shows the enzymes matched with their respective functions correctly ?

Study the DNA profiles obtained as a result of DNA fingerprinting of a child and three individuals 1, 2 and 3. Which one of the following options shows the probable parents of the child?

Select the option that gives the correct description of the process of Natural Selection with respect to the length of the neck of giraffe.

Select the option in which 325 mother cells undergo meiosis to produce the correct number of spores formed by the process of sporulation.

Choose the option that gives the correct number of pollen grains that will be formed after 325 microspore mother cells undergo microsporogenesis.

Given below are two columns. In Column I are the names of four contraceptive methods and in Column II are their contraceptive ways. Select the option in which the contraceptive methods are correctly matched with their functions.

Given below are two columns. In Column I the names of four contraceptive devices are given and in Column II the modes of action of the contraceptives are given. Select the option where the contraceptive devices are correctly matched with their respective modes of action.

In which one of the following options does the endocrine gland correctly match with its hormonal secretion and its function?

The organism used in construction of the first artificial recombinant DNA by Cohen and Boyer in 1972 was:

Who among the following challenged the patent right granted to the University?

Assertion (A): A patient of ADA deficiency undergoing treatment for gene therapy requires periodic infusion of genetically engineered lymphocytes. Reason (R): Lymphocytes are immortal.

Assertion (A): A cattle egret and grazing cattle in close association is a classic example of commensalism. Reason (R): As grazing cattle move through the field, they stir up and flush out insects from the vegetation that otherwise might be difficult for egrets to find and catch.

Assertion (A): Endosperm is completely consumed during the development of embryo in ex-albuminous seeds. Reason (R): Castor, pea and beans are all examples of ex-albuminous seeds.

Assertion (A): Birds like pigeon have heterogametic females whereas the males are homogametic. Reason (R): In pigeons, females have Z and W sex chromosomes whereas males have ZZ sex chromosomes.

The diagram given below shows a developmental stage of human embryo. Answer the following questions with reference to it: (a) Identify and name the human embryonic stage shown. (b) Mention its exact location in the normal pregnancy of a woman. (c) Write one function of each of the .

(a) From which end of the ovule, and how does the pollen tube gain its entry into the embryo sac of a Hibiscus flower? (b) State the fate of the male nuclei present in the pollen tube.

(a) (i) Identify them from the image given below: (ii) State their importance in various biotechnology experiments.

(b) Explain the process by which a bacterial cell can be made competent to take up foreign DNA from its surroundings by divalent cations and temperature treatment.

Ecological pyramids give important information about the ecological system, but they also have some limitations. List any two limitations of ecological pyramids.

India is the seventh largest country in the world in terms of area. It has 12% of the world's water and land area combined. What is the percentage of India's land area in the world? Give reason why India is one of the 12 mega-diverse countries of the world.

India is the seventh largest country in the world in terms of total land area including land and water. Write the value of the land area of our country (in terms of percentage) of the world. Mention then, what makes India one of the 12 mega diversity countries of the world.

With the help of only a schematic diagram, show the three steps involved in the construction of a recombinant DNA by the action of EcoRI and DNA ligase.

With the help of a schematic diagram only, show in three steps, the formation of recombinant DNA by the action of restriction endonuclease EcoRI and DNA ligase.

(a) Name the two primate ancestors of the present day humans, who existed approximately about 15 million years ago. (b) According to geological records, when and where did Australopithecines live? (c) Give two differences between Homo habilis and Homo erectus.

(a) (i) Expand the abbreviations given below, used for different modes of assisted reproductive technologies : (ii) Which one of them cannot be considered as a procedure of IVF ? Give reasons in support of your answer. OR (b) Differentiate between the following : (i) Perisperm and Pericarp (ii) Syncarpous pistil and Apocarpous pistil (iii) Plumule and Radicle

Gene expresses itself in a cell system as a protein/enzyme. How does an expression of gene occur in a cell system and when does it need to occur, and how the gene expression is regulated in a prokaryote cell system was studied by the combined efforts of Jacque Monod, the biochemist and Francois Jacob, the geneticist. For their work on lactose metabolism in E. coli a lac they were awarded the Nobel Prize in 1965. (a) Why is lac operon said to be a transcriptionally regulated system ? (b) It is said that the lac operon has to be operational at a very low level in the bacterial cell all the time. Justify. (c) Why is the regulator gene in lac ? (d) Draw a schematic diagram of lac operon in absence of inducer in the culture medium of the bacteria. OR (d) Draw a schematic diagram of lac operon in the presence of inducer in the culture medium of the bacteria.

Study the diagrammatic representation given below of the Earth with ... that follow. (a) Write the observations made regarding the species diversity when moving ... Give two reasons also. (b) Stating the reason, mention the approximate number of bird species recorded in India. OR (b) Name the region in the world that records the greatest biodiversity and mention why.

(a) Meselson and Stahl carried out an experiment to prove the nature of DNA replication. Recall the experiment and answer the following questions. (i) Which two types of nitrogen were used by them in their experiment and why ? (ii) Why did they tak

Study the diagrammatic representation given below of the Earth with s that follow. Write the observations made regarding the species diversity when moving . Give two reasons also.

Stating the reason, mention the approximate number of bird species recorded in India.

Name the region in the world that records the greatest biodiversity and mention why.

Meselson and Stahl carried out an experiment to prove the nature of DNA replication. Recall the experiment and answer the following questions.

Which two types of nitrogen were used by them in their experiment and why ?

Why did they take samples of E. coli at definite time intervals for their observation ?

State the role of caesium chloride density gradient in their experiment.

Write the conclusions they arrived at.

If the child is infected with the same pathogen almost four months later, the antibody concentration in his/her blood increases very fast. Explain why.

A table given below gives information about different types of immunity and how they are attained. Identify P, Q, R, S and T in the table.

Why is the consumption of smack considered as an abuse ? Name the source plant and one effect of the following drugs on the human body: (1) Marijuana (2) Cocaine (3) Morphine

Why is the consumption of smack considered as an abuse ?

Name the source plant and one effect of the following drugs on the human body: (1) Marijuana (2) Cocaine (3) Morphine

A table given below gives information about different types of immunity and how they are attained. Identify P, Q, R, S and T in the table. Type of immunity | Production of antibodies | Presence of memory cells | Mode attained (1) Natural, active | Yes | | (2) Natural, passive | No | Across the placenta during pregnancy/breast feeding | (3) Acquired, active | Yes | Getting a vaccine during breast feeding | (4) Acquired, passive | No | Getting an injection of antibodies

The given diagram shows three methods of pollen transfer in plants. What are the technical terms used for pollen transfer methods?

How do the following plants achieve pollination successfully? (1) Water lily (2) Vallisneria

Flowering plants have developed many devices to avoid inbreeding depression. Explain one hereditary and one physiological device which helps plants to achieve this target.

What are the suitable technical terms used for the following? (1) Days 1–7 (2) Days 8–12 (3) Days 16–28 (4) Days 13–15

Explain the role of ovarian and pituitary hormones during the following time periods: (1) Days 8–12 (2) Days 13–15 (3) Days 16–28