Students can access the CBSE Sample Papers for Class 12 Biology with Solutions and marking scheme Term 2 Set 4 will help students in understanding the difficulty level of the exam.
CBSE Sample Papers for Class 12 Biology Standard Term 2 Set 4 with Solutions
Time Allowed: 2 Hours
Maximum Marks: 40
General Instructions:
- All questions are compulsory.
- The question paper has three sections and 13 questions. All questions are compulsory.
- Section-A has 6 questions of 2 marks each; Section-B has 6 questions of 3 marks each; and Section-C has a case-based question of 5 marks.
- There is no overall choice. However, internal choices have been provided in some questions. A student has to attempt only one of the alternatives in such questions.
- Wherever necessary, neat and properly labeled diagrams should be drawn.
Section – A
Question 1.
Neutrophils and macrophages are called the soldiers and scavengers of animal body. Why?
Answer:
The neutrophils and macrophages tend to dispose the microbes and dead cells by feeding on such entities. The dead cells may clog the homeostasis of the body and the dead microbes may start to decompose in the animal body which will lead to toxicity. So, they are termed as soldiers and scavengers in the animal body.
Question 2.
A tumour is an abnormal growth of cells that serves no purpose. They can start in any one of the trillions of cells in our bodies. Tumours grow and behave differently, depending on whether they are cancerous (malignant), non-cancerous (benign) or precancerous. Differentiate between benign and malignant tumours.
OR
The figure below shows the production of antibiotic penicillin, identify the content A required for fermentation. Also identify the mould discovered by Alexander Fleming.
Answer:
| Benign tumour | Malignant tumour |
| 1. It is non-cancerous. | It is cancerous. |
| 2. It occurs by expansive growth. | It occurs by invasive growth. |
| 3. Mitotic activity of cells is not high. | Mitotic activity of cells is frequently high. |
| 4. There are no or few symptoms. | Symptoms are associated with pain and disability. |
| 5. No metastasis. For Example: Papilloma, Adenoma | Frequent metastasis. For Example: Liposarcoma, Adenocarcinoma |
OR
A-Media containing carbohydrates and amino acids
Alexander Flemming was the first to produce an antibiotic (named penicillin) from Penicillium notatum. The fungus is grown in a culture medium containing carbohydrates and amino acid. However, full potential as an effective antibiotic was established by Ernest Chain and Howard Florey.
Question 3.
Study the diagram showing the replication of HIV in humans and answer the following questions accordingly:
(i) Write the chemical nature of coat A’.
(ii) Name the enzyme ‘B’ acting on ‘X’ to produce molecule ‘C. Name ‘C’.
(iii) Mention the name of the host cell ‘D’ the HIV attacks first when it enters into the human body.
(iv) Name the two different cells where the new virus ‘E’ subsequently attack.
Answer:
(i) Chemically the structure of a coat shown in the diagram is viral protein coat.
(ii) Enzyme B is reverse transcriptase through which the viral DNA is produced. X is the viral RNA introduced into human cell and C is the viral DNA.
(iii) D-Macrophage is the host cell.
(iv) The two different cells the new virus ‘E’ subsequently attacks are macrophage and helper T-lymphocytes.
Question 4.
The global animal diversity is shown in the pie charts (A-Invertebrates and B-Vertebrates) drawn below:
(i) Identify the animal groups that are represented by the areas shaded black in A and B, respectively.
(ii) Of all the animal species recorded, what percent do insects comprise of?
Answer:
(i) A: Insects; B: Fishes
(ii) Among animals, insects are said to be the most species-rich taxonomic group. Insects are hexapod invertebrates belonging to phylum Arthropoda. Out of all known animal species, 70 percent is comprised of insects.
Question 5.
An exotic variety of Prickly pear introduced in Australia turned out to be intensive. How was it brought under control?
Answer:
The Prickly pear was controlled by using cactus feeding predator, a moth that feed on the plant.
Question 6.
Different animals respond to changes in their surroundings in different ways. Taking one example each, explain “some animals undergo aestivation while some undergo hibernation”. How do fungi respond to adverse climatic conditions?
OR
India is the seventh largest country in the world and Asia’s second largest nation, encompassing a varied landscape rich in natural resources. India has a great diversity of natural ecosystems from the cold and high Himalayan ranges to the sea coasts, from the wet north eastern green forests to the dry north western arid deserts, different types of forests, wetlands, islands and the oceans.
(i) Genetically different population with the same physical features is known as …………………
(ii) Xerocoles are:
Answer:
- Some animals go into aestivation to avoid summer related problems such as heat and dessication
e.g., snails or fish. - Some animals go into hibernation to avoid winter related problems e.g., polar bear.
- Fungi forms thick walled spores and suspend their activities to respond to adverse climatic conditions.
OR
(i) Ecotype
(ii) Animals adapted to live in deserts
Section – B
Question 7.
A sedative or tranquilliser is a substance that induces sedation by reducing irritability or excitement. They are central nervous depressants and interact with brain activity causing its deceleration. Various kinds of sedatives can be distinguished, but the majority of them affect the neurotransmitters, for example, morphine. Morphine is used as a sedative as well as a pain killer drug. Give an account on various uses of Morphine. What are the precautionary measures before using this drug? What are the side effects of this kind of drug?
OR
In which way has the study of biology helped us to control infectious disease?
Answer:
Morphine is used to help relieve moderate to severe pain. Morphine belongs to a class of drugs known as opioid (narcotic) analgesics. It works in the brain to change how the body feels and responds to pain. Precautions: Before taking morphine, tell your doctor or pharmacist if you are allergic to it, or to other opioid pain medications or if you have any other allergies. This product may contain inactive ingredients which can cause allergic reactions or other problems. Talk to your pharmacist for more details.
Side effects: The common side effects are nausea, vomiting, constipation, light- headedness, dizziness, drowsiness or sweating may occur. Some of these side effects may decrease after you have been using this medication for a while. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.
OR
It has helped us in many ways as follows:
- It has given knowledge to know the nature of disease.
- It has given information to search the mode of transmission and related vectors.
- It has provided treatment to the infected person through proper medication.
- Vaccination and immunisation for avoiding the spread of the disease have been developed.
Question 8.
Bacteria cannot be seen with the naked eyes, but these can be seen with the help of a microscope. If you have to carry a sample from your home to your biology laboratory to demonstrate the presence of microbes under a microscope, which sample would you carry and why?
Answer:
A sample of curd can be used to study the microbes under microscope. A drop of curd contains millions of bacteria. A curd contains Lactic Acid Bacteria called Lactobacillus. They digest and coagulate milk proteins by producing acids. Simple to study and easy to carry, a sample of curd can be preferred.
Question 9.
PCR (Polymerase Chain Reaction): It is the revolutionary method developed by Kary Mullis in the 1980s. PCR is based on using the ability of DNA polymerase to synthesise new strand of DNA complementary to the offered template strand. Because DNA polymerase can add a nucleotide only onto a pre-existing 3′-OH group, it needs a primer to which it can add the first nucleotide.
(i) Primer used for the process of polymerase chain reaction are:
(ii) Polymerase used for PCR is extracted from:
(iii) How many DNA duplex are obtained from one DNA duplex after 4 cycles of PCR?
Answer:
(i) Single stranded DNA oligonucleotide
(ii) Thermus aquaticus
(iii) 16
Question 10.
Water is very essential for life. Write any three features both of plants and animals which enable them to survive in water scarce environment.
Answer:
The first form of life originated in water. Water plays an essential role in various metabolic and catabolic processes of the organisms.
Plants survive in water scarce environment through:
(i) Completing the life cycle in a short period (Ephemeral mode).
(ii) Mechanisms like developing deep tap roots, deciduous leaves and sunken stomata to avoid transpiration loss. Also there is thick cuticular covering for this purpose.
(iii) Succulence to store the water.
In animals they possess the features like:
(i) Body avoids sweating to avoid loss of water.
(ii) The kidney functioning is uricotelic.
(iii) There is a fatty sebaceous deposition under the skin to avoid loss of water.
Question 11.
The graph given alongside shows the species area relationship. Study the graph and answer the following questions:
(i) Name the naturalist who showed this kind of relationship.
(ii) Name the region he explored.
(iii) Identify the situation when Z values are in the range of 0.6 to 1.2.
Answer:
(i) The naturalist who investigated the relationship shown in the graph was Alexander Von Humboldt.
He found that species richness increased within a region with an increase in the area explored, but only to a maximum.
(ii) Alexander von Humboldt explored wilderness of South American jungles.
(iii) Ecologists have discovered that the value of Z lies in the range of 0.1 to 0.2, regardless of the taxonomic group or the region (whether it is the plants in Britain, birds in California or molluscs in New York state, the slopes of the regression line are amazingly similar). But, if we analyse the species-area relationships among very large areas like the entire continents, the slope of the line to be much steeper (Z values in the range of 0.6 to 1.2).
Question 12.
Analyse the diagram given below and answer the questions based on it:
(i) What does the above diagrammatic representation concern about?
(ii) The diagram shows Step I, Step II and Step III. What are those?
(iii) What is the result at the end of the above process?
(iv) What are primers?
Answer:
(i) The diagram explains about the steps in PCR technique to amplify the gene of interest.
(ii) The Step I is Denaturation, Step II is Annealing and Step III is Extension.
(iii) At the end of PCR the result is an amplified DNA segment at the rate of 1 billion copies. Now, the amplified fragment can be used to ligate with the vector for further cloning.
(iv) These are small, chemically synthesised oligonucleotides which are complementary to the regions of DNA.
Section – C
Question 13.
Management of adult-onset diabetes is possible by taking insulin at regular time intervals. If a bacterium were available that could make human insulin, the whole process becomes so simple. Insulin used for diabetes was earlier extracted from pancreas of slaughtered cattle and pigs. Insulin from an animal source though caused some patients to develop allergy or other types of reactions to the foreign protein. Insulin consists of two short polypeptide Chains: Chain A and Chain B that are linked together by disulphide bridges.
Explain the various steps involved in the production of artificial insulin.
OR
The figure below depicts the result of blue-white screening in using lac Z as selectable marker.
Answer the following in reference to the figure :
(i) What is X -gal?
(ii) Lac Z codes for which enzyme? ,
(iii) What is the colour of the product of X-gal conversion in presence of functional lac Z?
(iv) What is the technique of inserting DNA in lac Z gene known as?
(v) Name a selectable marker used for screening in yeast cell.
Answer:
Steps involved in production of artificial insulin are:
- The plasmid of E.coli is removed and isolated using specific techniques.
- The isolated plasmid is opened by specified enzyme.
- In the open site of the bacterial plasmid the segment of DNA which codes for human insulin is inserted.
- After insertion, the plasmid is closed by using another special enzyme to make it a recombinant plasmid.
- This recombinant plasmid is again introduced into E. coli host cells.
- Now, E. coli cells become capable of synthesising human insulin. These bacteria are then cultivated in fermenters to produce a large amount of insulin.
- Insulin is then extracted from bacterial culture and purified
OR
(i) X-gal is an organic compound consisting of galactose linked to a substituted indole.
(ii) lacZ encodes p-galactosidase (LacZ), an intracellular enzyme that cleaves the disaccharide lactose into glucose and galactose.
(iii) The enzyme is well known to signal its presence by hydrolyzing X-gal to produce a blue product.
(iv) In some transformation experiments, a color-processing gene such as LacZ gene is utilized for confirmation of the molecular cloning (inserting a DNA fragment of interest into a plasmid vector). Plasmids with an uninterrupted LacZ gene turn their bacteria blue.
(v) URA3, an orotidine-5′ phosphate decarboxylase from yeast is a positive and negative selectable marker.