HBSE Class 12th Biology Sample Paper 2024 Answer

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HBSE Class 12th Biology Sample / Model Paper 2024 Answer

Class – 12th                         Subject – Biology
Time : 3 Hours                      Total Marks : 70

General instructions –
1. All questions are compulsory.
2. The question paper has five sections and 35 questions.
3. Section A has 18 questions of 1 mark each, Section B has 7 questions of 2 mark each, Section C has 5 questions of 3 marks each, Section D has 2 case study based questions of 4 marks each, Section E has 3 questions of 5 marks each.
4. 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.
5. Where ever necessary, neat and properly labeled diagrams should be drawn.

SECTION – A (18 Marks)
(18 Questions of 1 Marks Each)

1. Choose the right one among the statements given below :
(a) IUDs are generally inserted by user herself.
(b) IUDs increase phagocytosis reaction in uterus.
(c) IUDs suppress gametogensis.
(d) IUDs once inserted need not be replaced
Answer – (b) IUDs increase phagocytosis reaction in uterus.

2. Hormones released by placenta are :
(a) hPL, hCG, oxytocin
(b) hCL, hPL, prolactin
(c) hCG, hPL, estrogen, progestrone
(d) hPL, hCG, estrogen, progestrone, relaxin
Answer – (d) hPL, hCG, estrogen, progestrone, relaxin

3. Test cross involves :
(a) crossing of F1 hybrid with a homozygous recessive genotype.
(b) crossing between F1 hybrids.
(c) crossing between two genotype with recessive traits.
(d) crossing between two genotype with dominant traits.
Answer – (a) crossing of F1 hybrid with a homozygous recessive genotype.

4. Human chromosomes with highest and least number of genes are :
(a) Chromosome 21 and Y
(b) Chromosome 1 and X
(c) Chromosome 1 and Y
(d) Chromosome X and Y
Answer – (c) Chromosome 1 and Y

5. Evolutionary history of any organism is known as :
(a) Palaeontology
(b) Phylogeny
(c) Ontology
(d) Ancestry
Answer – (b) Phylogeny

6. AIDS is caused by HIV. HIV does not spread by which of the following mean :
(a) Transfusion of contaminated blood.
(b) Sharing of infected needles.
(c) Shaking hands with infected person.
(d) Sexual contact with infected person.
Answer – (c) Shaking hands with infected person.

7. An example of endomycorrhiza :
(a) Glomus
(b) Rhizobium
(c) Agaricus
(d) Nostoc
Answer – (a) Glomus

8. PCR is most useful in :
(a) DNA synthesis
(b) Protein synthesis
(c) DNA amplification
(d) Amino acid synthesis
Answer – (c) DNA amplification

9. A transgenic animal has :
(a) Foreign DNA in its cells
(b) Foreign RNA in its cells
(c) Foreign DNA in some of its cells
(d) Both B and C
Answer – (a) Foreign DNA in its cells

10. A protozoan reproduce by binary fission. What will be the number of protozoan after six generation :
(a) 24
(b) 128
(c) 64
(d) 32
Answer – (c) 64

11. Interaction between fig tree and wasp is :
(a) Parasitism
(b) Mutualism
(c) Commensalism
(d) Predation
Answer – (b) Mutualism

12. Red Data book contains :
(a) Useful plants
(b) Useful animals
(c) Endangered species
(d) Both A and B
Answer – (c) Endangered species

13. Which of the following is a false fruit :
(a) Banana
(b) Orange
(c) Apple
(d) Mango
Answer – (c) Apple

14. Sickle cell anemia is an example of :
(a) Point mutation
(b) Autosomal recessive disorder
(c) Mendelian disorder
(d) All of these
Answer – (d) All of these

Q15–Q18 Assertion Reason based questions :
Answer these questions by choosing right option.
(a) Both A and R are true an R is right explanation of A
(b) Both A and R are true an R is not right explanation of A
(c) A is true and R is false
(d) A is false and R is true

15. Assertion A : A community constitute the biotic component of ecosystem.
Reason R : Different type of organism’s i.e. plants and animals together makes a community.
Answer – (a) Both A and R are true an R is right explanation of A

16. Assertion A : Chemical pesticides are comparatively hazardous than biopesticides.
Reason R : Biopesticides degrade the environment quickly.
Answer – (c) A is true and R is false

17. Assertion A : One gene one enzyme hypothesis is applicable universally.
Reason R : One enzyme may contain one and more than one polypeptide chains.
Answer – (d) A is false and R is true

18. Assertion A : All the individuals of purelines are heterozygous.
Reason R : A heterozygous individual has two dissimilar forms of an allele.
Answer – (d) A is false and R is true

SECTION – B (14 Marks)
(7 Questions of 2 Marks Each)

19. Name the organic material found in exine layer of cell wall of pollen grain? Write down its advantage of it for pollen grain.
Answer – ‘Sporopollenin’ is found in exine layer of cell wall of pollen grain. Exine protect the pollen from dessication, acids and extreme weather condition thus increase its viability.

20. What is point mutation? Give example of it.
Answer – The mutation that is caused by addition, deletion or substitution of single base pair is called point mutation. Example: sickle cell anemia is caused by point mutation where single base substitution changes codon GAC to GUG.

21. Wings of a bird and wings of butterfly are either analogous or homologous organ? Also tell the kind of evolution they represent.
Answer – Wings of a bird and wings of butterfly are analogous organs. These show convergent evolution where different structures are evolved for same function.

22. What is GEAC? Write down its objectives.
Answer – GEAC refers to ‘Genetic Engineering Approval Committee’. GEAC made decision regarding validation of GMO research and safety of introducing these GMO for public service.


If we don’t follow genetic barriers while creating GMO, it can be dangerous. Do you agree with this statement ?
Answer – Yes, we agree with this statement as if genetic barriers are not used for creating GMO this can be dangerous as these organism can cause a threat to natural flora and fauna may lead to loss of biodiversity, cause ecological imbalance pose threat to our environment.

23. A person is advised antiretroviral therapy, which infection is he suffering from? Name the causative organism for this disorder.
Answer – The person may be affected by AIDS (Acquired Immuno Deficiency Syndrome). AIDS is caused by HIV-virus (Human immunodeficiency virus). It has RNA as genetic material i.e. it is a retrovirus.

24. (a) What is triple fusion? Name the nuclei involve in it.
Answer – Fusion of two polar nuclei and one male gamete is called triple fusion. It occurs in embryo sac.


(b) Why apomixis is preferred to produce seeds in hybrid crops ?
Answer – Apomixis is preferred to produce seeds in hybrid crops as in this technique as :
• seeds are formed without fertilization so no segregation of useful character.
• cost and time of seed production is reduced.

25. Explain how XXY individuals can arise in human beings? Name the disorder and its symptoms ?
Answer – XXY karyotype can be produced by gaining extra copy of X chromosome. This is known as Klinefelter Syndrome. Such individual are males with feminine characters like Gynaecomastia. They are generally sterile.

SECTION – C (15 Marks)
(5 Questions of 3 Marks Each)

26. How Hugo De Vries theory of evolution differs from Darwin Theory of evolution ?
Answer – Hugo De Vries believe in sudden or random mutation at large scale that cause speciation. He proposed saltation as basis of evolution.
On other hand Darwin theory of Natural selection is based on slow and inheritable mutation. These mutations form the basis of variation in population. Nature select the fittest organism.

27. (a) Why diseases like Tuberclosis, cholera, typhoid spread more commonly in crowded areas ?
Answer – T.B, Cholera are communicable diseases that spread via air, water so in crowded areas there transmission can happen easily.

(b) What are vectors and pathogens ?
Answer : Vectors – Vectors are the organisms like insects that help in transmission of the pathogen e.g. flies, mosquitoes etc.
Pathogens – Pathogens are diseases causing micro organisms e.g. Salmonella typhi that causes typhoid.

28. What is advantage of genetically synthesized insulin over traditionally synthesized insulin? Name the organism used to produce this insulin ?
Answer – Genetically synthesized insulin does not cause allergy. Easy and economical production by rDNA technology. Insulin is produced by transgenic E.coli.


(a) Name the nematode that infests the tobacco plant and the part that it infests.
Answer – Meloidegyne incognito (Roots)

(b) How is Agrobacterium used to protect tobacco plant from this attack ?
Answer – By using Agrobacterium vector nematode specific genes were introduced into host plant, introduction of DNA produce both sense and anti-sense strand of RNA that being complementary to each other, this ds RNA initiated RNAi and silenced the specific mRNA of nematode, hence parasite could not survive in host.

29. Why energy pyramids in a food chain are never inverted although pyramids of number can be inverted? Explain.
Answer – The energy that passes from one trophic level to next trophic level is only 10%. This is called 10% law of energy. So the amount of energy at first level will greater as compared to the energy at last tropic level that why energy pyramids are always upright.

30. (a) Why tropics have greater species diversity ?
Answer – Tropics have greater amount of sunlight throughout the year. It has ample rainfall. It do not face any natural environmental disturbances, so it shows greater biodiversity

(b) Which is better method of conservation of biodiversity according to you in-situ or ex-situ ?
Answer – According to me in-situ conservation is better mode as it follows the conservation of organism in its natural condition so help to maintain the ecological balance in the biosphere.


Which approach of biodiversity conservation do you feel is more comprehensive to understand the importance of biodiversity broad utilitarian or narrow utilitarian ?
Answer – The broad utilitarian approach for biodiversity conservation is more comprehensive as it considers the ecological relationship between different communities hence give us a broader approach to understand the environment. For example, it helps to understand :
• the relationship of pollinator and plant
• relationship like predation and competition
• to maintain ecological balance
• relationship of forest with rainfall and soil erosion etc.

SECTION – D (8 Marks)
(2 Case Study Questions of 4 Marks Each)

31. Case Study Based 1 :
Overall ability to fight the disease causing agents is called immunity. It is of two types. One is of non specific type and another is of specific type. Immune response in specific type of immunity is because of two type of lymphocytes. One of these cells produce protein bodies called antibodies which counteract the pathogen. When a host is exposed to antigen, antibodies are produced in its body. Preformed antibodies are administered to develop immunity in some cases. Sometime immune system shows exaggerated response to certain antigen. These antigens are called allergens.
(a) What are interferons ?
Answer – Interferons are the proteins that activate the immune system and helps to destroy the tumors.

(b) Name the anti body found in colostrum ?
Answer – Antibody IgG

(c) Name the lymphocytes that produce antibodies ?
Answer – B lymphocytes produce antibodies. T lymphocytes help B lymphocyte to produce antibodies.


(d) Differentiate between active immunity and passive immunity ?
Answer – Active immunity is based upon principle of antigen antibody reaction where organism produce antibody on interaction with antigen. Readymade antibodies are given to protect the body in passive immunity.

32. Case Study Based 2 :
Reproductive Health refers to a total well being in all aspect of reproduction. i.e. physical, social, imotional and behavioral. Our nation was the first nation in the world to initiate various action plan at world level towards attaining reproductively healthy society. Counselling and creating awareness among people about reproductive organs,adolescence and associated changes, safe and hygienic sexual practices, sexually transmitted diseases is the primary step towards reproductive health. Providing facilities to control STDs, medical termination of pregnancy, birth control, infertility, delivery, post natal child and maternal management is another aspect of reproduction and child care health.
(a) In which year the family planning programs were initiated ?
Answer – In year 1952

(b) What do you think that awareness regarding reproductive health can help to prevent STDs ?
Answer – Awareness regarding reproductive health can help the individual to better understand the etiology of STDs, hence help him to protect from these.


(c) Write major task of RCH programme.
Answer – The major task of RCH programme is to create awareness about a reproduction aspect and providing facilities for building a reproductively healthy society.

(d) Name any STD.
Answer – Syphilis and Gonorrhea

SECTION – E (15 Marks)
(3 Questions of 5 Marks Each)

33. What are the phases of menstrual cycle? What happens if an egg is fertilized ?
Answer – Three phases of menstrual cycle are :
(a) Menstrual phase –
• Discharge of mucous blood and endometrial lining through vagina.
• Occurs for 3-5days.
• Mark the start of menstrual cycle.
(b) Follicular phase –
• one of the primary follicles in ovary grows to mature Graafian follicle.
• Endometrium proliferate.
• Estrogen level increases and reaches the peak level in the middle of the cycle (14th day).
(c) Luteal phase –
• Gratian follicle rupture and ovum is released (ovulation).
• Corpus luteum formed to release progesterone.
• Endometrium continue to proliferate under effect of progesterone.
(d) If fertilization occurs it leads to implantation otherwise the unfertilized egg is released and it marks the beginning of another cycle.


Write in brief about: (a) Implantation; (b) male accessory ducts.
Answer – (a) Implantation – After fertilization the zygote undergo cleavages in the oviduct and it forms 16 cells called blastomeres this stage is called morula. The morula continues to divide and transform in to blastocyst. In blastocyst outer layer of blastomeric form trophoblast and inner cell form inner cell mass. Trophoblast get attached to endometrium and after attachment the uterine cells divide rapidly so the blastocyst become embedded in endometrium this is called implantation.
(b) Male accessory ducts – Male accessory gland includes seminal vesicles prostate gland and bulbourethral glands. Secretion of these glands constitutes seminal plasma that has fructose calcium and may enzymes. Secretion of bulbourethral gland helps in lubrication of penis.

34. What is semi conservative mode of replication? Explain Messelson and Stahl experiment to prove semi conservative replication ?
Answer – During DNA replication each newly synthesized DNA has one parental strand and one newly synthesized strand. This is called semi conservative replication. Since nitrogen is a part of DNA so Stahl and Messelson use heavy nitrogen in place of normal nitrogen
(a) Meselson and Stahl grew E.coli on heavy Nitrogen isotope for many generations. So that N¹⁵ is incorporated into its DNA. Then transferred E.coli to medium containing N¹⁴ and allow them to grow.
(b) The DNA in first generation has intermediate density as compared to parental DNA. The density was measured by cesium chloride density gradient method
(c) DNA in second generation has half normal density and half intermediate density DNA strand. This shows semi conservative replication.


(a) Explain in two lines: (1) Promoter; (2) Coding strand; (3) Polymorphism
Answer – (1) Promoter – The sequence that is located upstream means 5′ end of structural gene that provide binding site of RNA polymerase. The presence of promoter marks the template strand as it is present on template strand.
(2) Coding Strand – The strand of DNA that has polarity 5′ to 3′ is displaced during transcription and it does not code for RNA is called coding strand.
(3) Polymorphism – Polymorphism is variation at genetic level due to mutation. These mutations in germ cell are inheritable. These mutations keep on accumulating and form the basis of polymorphism. When such inheritable mutation are observed in a population at high frequency this is called DNA polymorphism. Polymorphism may range from single nucleotide to large scale.

(b) Write salient feature of Human Genome Project.
Answer – Human Genome Project :
• Genome contains 3164 million nucleotides
• Average gene consist of 3000 bases
• Total number of genes is App. 30000
• Function of 50% gene is unknown
• Less than 22% of genome code for proteins

35. (a) How are reporter enzyme help to monitor transformed cells in addition to selectable marker ?
Answer – The reporter gene help to select the transformant cells by insertional inactivation of the enzyme gene. For example, the insertional inactivation of enzyme β galactosidase in E.coli leads to formation of colourless colonies when grown on a chromogenic substrate while non transformant produce blue colonies.

(b) Explain gel electrophoresis.
Answer : Gel electrophoresis – Process to separate the DNA fragments according to their molecular size by applying electric field across the agarose gel. DNA is negatively charged that will moves towards anode, smaller sized fragments move faster, fragments can be visualized under UV radiation as bright orange band due to dye Ethidium bromide. Desired DNA is obtained by elution process.


Look at the diagram and identify the process. Explain the process and also write its applications.

Answer – The technique shown in picture is PCR (Polymerase chain reaction). PCR is used to amplify the DNA fragments of interest. DNA polymerase used in process is obtained from bacterium Thermophilus aquaticus that does not get denatured and polymerise at high temperature.
• Denaturation : heating of DNA at high temp (94-98° Celsius) to isolate both strands
• Annealing : annealing of primers for synthesis of new strands
• Extension : DNA polymerase binds to primer and polymerise new strands
• Detection of pathogenic micro organism
• Amplification of DNA
• in DNA analysis

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