CBSE(NCERT) GRADE 12 BIOLOGY 2023 SET3

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.

The first gene-sequenced crop is :

Identify the region and process of transcription in prokaryote as shown in the schematic representation given below.

Study the DNA profiles obtained as a result of DNA fingerprinting of a child and three other individuals. Which of the following options shows the probable parents?

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

Which of the following samples of DNA in the table given below will give the desired result during polymerase chain reaction?

Which of the following is used to inactivate the desired gene?

Which one among the following is the desired gene?

Which one among the following biofertilizers does not fix atmospheric nitrogen?

Examples that show commensalism are:

Assertion (A): A species of wasp and a fig species cannot complete their life cycle without each other. Reason (R): While visiting wasps come to lay eggs in the fig inflorescence, the flower of wasp gets pollinated in return.

Assertion (A): For sequencing, the total DNA from a cell is isolated and converted into random fragments. Reason (R): DNA is a very long polymer.

Assertion (A): In order to cut the DNA with a restriction enzyme, it needs to be released from the membrane which encloses it. Reason (R): A plant cell was treated with chitinase to achieve this.

Assertion (A): Darwin showed how even a slow growing animal like an elephant could reach enormous numbers. Reason (R): When resources in the habitat are unlimited, each species has the ability to realise its innate potential fully.

(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) Mention the main objective of the Ramsar Convention. (b) Name any two sites in India that are important in the Ramsar Convention.

(a) Why should antibiotics not be taken indiscriminately? Give any two reasons. (b) It is advisable to complete the course of antibiotics as prescribed by the doctor. Justify.

(a) (i) Identify the image given below and name it. (ii) State their importance in various biotechnology experiments. OR (b) Explain the process by which a bacterial cell can be made competent by using divalent cations and temperature treatment.

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 parts labelled X, Y and Z.

(i) Expand the abbreviations given below, used for different modes of assisted reproductive technologies:

Which one of them cannot be considered as a procedure of IVF? Give reasons in support of your answer.

Explain the following in the context of treatment of waste water in an effluent treatment plant: (a) Primary sludge (b) Activated sludge (c) Anaerobic sludge digester

Differentiate between the following: (i) Perisperm and Pericarp (ii) Syncarpous pistil and Apocarpous pistil (iii) Plumule and Radicle

Treatment of wastewater is done in a sewage treatment plant to make it less polluting. Explain the following with reference to this treatment process: (a) Primary sludge (b) Activated sludge (c) Anaerobic sludge digesters

(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.

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) Differentiate between malignant and benign tumours. (b) Name and explain the most feared property of a malignant tumour.

(a) . (b) From where can one obtain in humans ? (c) State any two applications of stem cells in curing human diseases.

Study the pedigree chart of a family given below and answer the questions that follow: (a) Is the disease in this pedigree chart a recessive or dominant disorder? Give reason. (b) Identify the female individual in this family, who for sure is homozygous. (c) Genotype of which one individual cannot be identified in this pedigree chart? (d) Identify a male who is definitely heterozygous. (e) Is this disease a sex-linked or an autosomal disorder?

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 lac 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 the following questions that follow. (a) Write the observations made regarding the species diversity when moving from the equator towards the poles. 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) A time-bound vaccination programme is followed for the children in our country from their birth up to ten years of age. A graph plotted below shows the effect of the vaccination followed by infection by the same pathogen, and the antibody concentration in the blood of the child. (i) Explain why the administration of a vaccine causes an increase in the antibody concentration. (ii) 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. (iii) The following table gives information about different types of immunity and how they are acquired. Identify and complete the table.

Explain why the administration of a vaccine causes an increase in the antibody concentration.

You are given a long pea plant and asked to determine its genotype. Which cross would you use to obtain the probable genotype of the given long pea plant? Name it and explain.

(a) (i) Describe the phenomenon of adaptive radiation as explained by Darwin. (ii) Is human evolution an example of adaptive radiation? Give reason in support of your answer.

(b) You are given a tall pea plant and asked to determine its genotype. Name and explain the cross that you will carry out to find the possible genotype of the given tall pea plant.

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.

The 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

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

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

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

Observe the diagram given below showing the menstrual cycle of a normal human female and answer the questions that follow: What are the suitable technical terms used for the following?

Observe the diagram given below showing the menstrual cycle of a normal human female and answer the questions that follow: Explain the role of ovarian and pituitary hormones during the following time periods: