Please refer to the Class 12 Biology Sample Paper below. These CBSE Sample Papers for Class 12 Biology have been prepared based on the latest guidelines and examination patterns issued for the current academic year. We have provided Term 1 and Term 2 sample papers with solutions. You can click on the links below and access the free latest CBSE Sample Papers for Biology for Standard 12. All guess papers for Biology Class 12 have been prepared by expert teachers. You will be able to understand the type of questions which are expected to come in the examinations and get better marks.
CBSE Sample Papers for Class 12 Biology
Class 12 Biology Sample Paper Term 2 With Solutions Set A
SECTION-A
1. (i) Given below are pairs of diseases and causative organisms. Which out of these is not a matching pair?
Filariasis : Wuchereria, Ringworm : Ascaris, AIDS : Human immuno virus, Malaria : Plasmodium.
(ii) Highlight the role of thymus as a lymphoid organ. Name the cells that are released from the above mentioned gland. Mention how they help in immunity.
Answer : (i) Ringworm : Ascaris.
(ii) Thymus T–lymphocytes mature in thymus, and responsible for both cellular and humoral immune response
2. In which way have microbes played a major role in controlling diseases caused by harmful bacteria? Name any one such substance and its source organism.
Answer : Some microbes produce chemicals – Antibiotics – that prevent multiplication of bacterial population allowing hosts to fight against infection, which is done by stopping the mechanism responsible for building cell wall. For example, Penicillium notatum produces penicillin.
OR
Explain the significant role of the genus Nucleopolyhedrovirus in an ecological sensitive area.
Answer : Baculoviruses are pathogens that attack insects and other arthropods.
• The majority of baculoviruses used as biological control agents are in the genus Nucleopolyhedrovirus.
• These viruses are excellent candidates for species-specific, narrow spectrum insecticidal applications.
• They have been shown to have no negative impacts on plants, mammals, birds, and fish or even on non-target insects.
• This is especially desirable when beneficial insects are being conserved to aid in an overall integrated pest management (IPM) programme, or when an ecologically sensitive area is being treated.
3. What is the role of Recombinant DNA technology for preparing vaccines.
Answer : Recombinant DNA technology has allowed the production of antigenic polypeptides of pathogen in bacteria or yeast. Vaccines produced using this approach allow large scale production and hence greater availability for immunisation, e.g., hepatitis B vaccine produced from yeast.
4. Name the blank spaces a, b, c, and d in the table given below:
| Type of microbee | Name | Commercial Product |
| Fungus | a | Penicillin |
| Bacterium | Acetobacter aceti | b |
| c | Clostridium butylicum | d |
| Yeast | e | citric acid |
Answer : a-Penicillium notatum, b-vinegar [acetic acid], c-bacterium, d-butyric acid, e-Aspergillus nige
5. How many biosphere reserves, national parks and wildlife sanctuaries do we have in India? Which approach do they cover for conservation of biodiversity? 2
Answer : In India, ecologically unique and biodiversity-rich regions are legally protected as biosphere reserves, national parks and sanctuaries. India now has 14 biosphere reserves, 90 national parks and 448 wildlife sanctuaries.
6. (i) If 8 individuals in a laboratory population of 80 fruitflies died in a week, then what would be the death rate for population for the said period?
(ii) In a pond, there were 200 frogs. 40 more were born in a year. Calculate the birth rate of the population.
Answer : Death rate = Number of individuals died / Total number of individuals
The birth rate of frog population = 8 /80 = 0.1 individuals/week = 40 /200 = 0.2 per frog/year
OR
What is age pyramid? List any two informations given by them. Draw an age pyramid of an expanding population.
Answer : (i) Death rate will be 0.1 individuals/week.
(ii) 200 per thousand/year.
Age pyramid–When the age distribution (per cent individuals of a given age or age group) is plotted for the population, this is called age pyramid.
Information given-
• Population at any given time is composed of individuals of different ages.
• For human population, the age pyramids generally show age distribution
of males and females in a combined diagram.
• The shape of the pyramids reflects the growth status of the population that whether it is expanding (triangular shaped), stable (bell-shaped) or declining.
SECTION-B
7. (i) Name and explain giving reasons, the type of immunity provided to the newborn by the colostrum and vaccinations.
(ii) Name the type of antibody
(a) Present in colostru
(b) Produced in response to allergens in human body.
Answer : (i) Colostrums provides passive immunity, direct antibodies are transferred from mother to new born via colostrums and vaccines are in the form of living or dead microbes or their proteins which when introduced in body activates active immune system of the body. Body starts producing antibodies and protecting from further infections.
(ii) (a) IgA; (b) IgE
OR
Identify A, B and C in the schematic diagram of an antibody given above and answer the questions.
(i) Write the chemical nature of an antibody.
(ii) Name the cells that produce antibodies in humAnswer :
(iii) Mention the type of immune response provided by an antibody.
Answer : A – Antigen binding site, B – Light chain, C – Heavy chain,
(i) Antibodies are proteinaceous in nature.
(ii) B-lymphocytes
(iii) Humoral immune response
8. Drug addicts are vulnerable to getting infected by a deadly virus. Name the virus and explain the mechanism that may result into infection.
Answer : Human Immuno Deficiency virus as the drug addicts share the needles to inject the drugs very often.
The HIV virus attacks the macrophages cells in human body.
(i) RNA is replicated to form viral DNA by the enzyme reverse transcriptase.
(ii) Viral DNA now gets incorporated into the host cell’s DNA and directs the infectedcell s to produce viruses.
(iii) Macrophages continue to produce virus particles and function as HIV factories.
(iv) The virus particles enter helper T-lymphocytes in the blood, where they continue to replicate and produce viral progenies.
(v)The number of helper T-lymphocytes progressively decreases in the body of the infected person.
(vi) With the decrease in number of T-cells, the immunity also decreases. The person is unable to produce any immune response even against common bacteria like Mycobacterium, parasites like Toxoplasma, viruses and fungi.
9. What happens when Meloidegyne incognita consumes cells with RNAi gene? Explain.
Answer : Several nematodes parasitize a wide variety of plants and animals including human beings.
A nematode Meloidegyne incognitia infects the roots of tobacco plants and causes a great reduction in yield. A
novel strategy was adopted to prevent this infestation which was based on the process of RNA interference (RNAi).
RNAi takes place in all eukaryotic organisms as a method of cellular defense. This method involves silencing of a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRNA (silencing). The source of this complementary RNA could be from an infection by viruses having RNA genomes or mobile genetic elements (transposons) that replicate via an RNA intermediate.
10. (i) Write the importance of measuring the size of a population in a habitat or an ecosystem.
(ii) Explain with the help of an example, how the percentage cover is a more meaningful measure of population size than mere numbers?
Answer : (i) Measurement of population in a habitat determines the relative abundance of a particular species and its effect on the available resources of that particular habitat.
(ii) The percentage cover is more meaningful measure of population size than mere numbers because the relative abundance of a species is not only determined by number of individuals but by both the relative abundance in biomass and number.
For example, in a unit area the number of grass species or relative abundance in number is high but not the relative biomass, if the same area has one or two Ficus bengalensis tree, it is very low in relative abundance but high in relative abundance of biomass.
11. For many decades, ecologists believed that communities with more species, generally, tend to be more stable than those with less species. What exactly is stability for a biological community?
What is the importance of species diversity for human beings?
Answer : A stable community should not show too much variation in productivity from year to year; it must be either resistant
or resilient to occasional disturbances (natural or man-made), and it must also be resistant to invasions by alien species. David Tilman’s long-term ecosystem experiments using outdoor plots found that plots with more species showed less year-to-year variation in total biomass. He also showed that in his experiments, increased diversity contributed to higher productivity. Rich biodiversity is not only essential for ecosystem health but imperative for the very survival of the human race on this planet.
12. What are the differences in lab cultures and the continuous cultures? What is a recombinant protein?
Answer : The cells harbouring cloned genes of interest may be grown on a small scale in the laboratory. The cultures may be used for extracting the desired protein and then purifying it by using different separation techniques. In lab cultures can’t be done at large scale or for long period of time as culture medium gets contaminated by wastes produced by cells being cultured.
In a continuous culture system wherein the used medium is drained out from one side while fresh medium is added from the other to maintain the cells in their physiologically most active log/exponential phase. Such procedures are generally followed at commercial or industrial level.
If any protein encoding gene is expressed in a heterologous host, is called a recombinant protein.
SECTION-C
13. Read the paragraph and answer the questions that follow.
The ability to manipulate the most basic genetic information, DNA, has resulted in an exponential increase in the number of tech companies using recombinant DNA. Biotechnology is used in four major industries, healthcare, agriculture and crop production, non-food (industrial) application of crops and other products (for example, vegetable oil, biodegradable plastics, biofuels) and environmental uses. Many pharmaceuticals are already made using synthetic enzymes and microorganisms; these are products which contain substances such as insulin, interferon or activating plasmids and which were very complicated or very expensive to manufacture in the past.
The first applications of enzymes in the biotechnology industry were manufacturing sweeteners (such as obtaining fructose syrup from wheat) and the use of lipases and proteases in detergents for removing difficult stains.
(i) Explain five area s where biotechnology has influenced human lives.
(ii) Name two enzymes that are used in household products in our daily life.
(iii) Name a life saving drug that had been extracted from animals earlier but later was manufactured at mass scale by inserting its genes in E.coli, pioneered by Eli Lilly. Discuss how it was successfully done by his company.
Answer : (i) Genetically modified crops with high nutritive value are provided by biotechnology.
• It has helped in the production of recombinant vaccines.
• It has devised techniques such as gene therapy for the treatment of genetic diseases.
Genetically engineered microbes are produced to control environmental pollution.
Transgenic animals are developed that can produce human proteins.
(ii) • Lipases in detergents
• Proteases and pectinases in fruit juices
(iii) 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.
In 1983, Eli Lilly an American company prepared two DNA sequences corresponding to A and B, chains of human insulin and introduced them in plasmids of E. coli to produce insulin chains. Chains A and B were produced separately, extracted and combined by creating disulphide bonds to form human insulin.
OR
Herbert Boyer performed studies on a couple of enzymes of the E. coli bacterium that have the capability of cutting DNA strands in a particular fashion, which left what has became known as ‘sticky ends’ on the strands. This discovery, in turn, led to pioneering work by Stanley Cohen. Cohen had been studying plasmids and had developed a method of removing them from the cell and then reinserting them in other cells. Combining this process with that of DNA splicing enabled Boyer and Cohen to recombine segments of DNA in desired configurations and insert the DNA in bacterial cells, which could then act as manufacturing plants for specific proteins.
Before Boyer and Cohen could isolate the recombinant plasmid they wanted, they need to way to get their ligated plasmids into E coil. Classic experiments by Oswald Avery and his group that Preumococcus bacteria are “transformed“ to virulence when they take up DNA from virulent strains.
(i) Which enzymes are being referred to in the paragraph? How sticky ends are formed by them, depict through a diagram?
(ii) What are some enzymes called“molecular scissors”? Give one example. How do they perform its job?
(iii) Explain the nomenclature of an endonuclease by taking an example?
Answer : (i) Restriction enzymes. Eco RI is used to cut a segment of foreign DNA and that of a vector DNA to form a recombinant DNA.
(ii) The restriction endonucleases are called“molecular scissors” as they can cleave the DNA like scissors can cut paper or fabric that too at specific locations. These restriction endonucleases used in genetic engineering to join DNA from different sources.
(iii) EcoRI
E first letter of genus Eschirichia
co two letter of species coli
R from strain RY13
I order of its discovery in roman numerals
