CBSE Sample Papers for Class 12 Biology Paper 2

These Sample papers are part of CBSE Sample Papers for Class 12 Biology. Here we have given CBSE Sample Papers for Class 12 Biology Paper 2.

CBSE Sample Papers for Class 12 Biology Paper 2

Board	CBSE
Class	XII
Subject	Biology
Sample Paper Set	Paper 2
Category	CBSE Sample Papers

Students who are going to appear for CBSE Class 12 Examinations are advised to practice the CBSE sample papers given here which is designed as per the latest Syllabus and marking scheme as prescribed by the CBSE is given here. Paper 2 of Solved CBSE Sample Paper for Class 12 Biology is given below with free PDF download solutions.

Time Allowed: 3 hours
Maximum Marks: 80

General Instructions:

1. There are total 26 questions and five sections in the question paper. All questions are compulsory.
2. Section A contains question number 1 to 5, Very Short Answer Type Questions of one mark each.
3. Section B contains question number 6 to 10, Short Answer Type Questions of two marks each.
4. Section C contains question number 11 to 22, Short Answer Type Questions of three marks each.
5. Section D contains question number 23, Value Based Question of four mark.
6. Section E contains question number 24 to 26, Long Answer Type Questions of five marks each.
7. There is no overall choice in the question paper, however, an internal choice is provided in one question of two marks, one question of three marks and all three questions of five marks. An examiner is to attempt any one of the question out of the two given in the question paper with the same question number.
8. No. of printed pages are three.

SECTION-A

Question 1.
Observe the pedigree chart and answer the following questions:
(a) Identity whether the trait is sex linked or autosomal.
(b) Give an example of a disease in human beings which shows such a pattern of inheritance.

Question 2.
Identify the reason for the selection of DNA polymerase from Thermus aquaticus for Polymerase Chain Reaction

Question 3.
Govt, of India has raised the marriageable age of females to 18 yrs and of males 21 yrs. Suggest any two measures adopted by the government for the purpose.

Question 4.
Thymus of a new born child was degenerating right from birth due to genetic disorder. Predict its two impacts on the health of the child.

Question 5.
Give an example of a chromosomal disorder caused due to non-disjunction of autosomes

SECTION-B

Question 7.
A single pea plant in your kitchen garden produces pods with seeds, but the individual papaya plant does not. Explain.

Question 8.
Suggest four important steps to produce a disease resistant plant through conventional plant breeding technology.

Question 9.
Name a genus of baculovirus. Why are they considered good biocontrol agents?

Question 10.
Explain the relationship between CFCs or Ozone in the stratosphere.

OR

Why are sacred groves highly protected?

SECTION-C

Question 11.
Why is breast feeding recommended during the initial period of an infant’s growth? Give reasons.

Question 12.
Give an example of an autosomal recessive trait in humans. Explain its pattern of inheritance with the help of a cross.

Question 13.
Describe the experiment that helped Louis Pasteur to dismiss the theory of spontaneous generation of life

Question 14.
Plant breeding technique has helped sugar industry in North India. Explain how.

Question 15.
Suggest and describe a technique to obtain multiple copies of a gene of interest in vitro.

Question 16.
What is GMO? List any five possible advantages of a GMO to a farmer.

Question 17.
During a school trip to ‘Rohtang Pass’, one of your classmate suddenly developed “altitude sickness”. But, she recovered after sometime.
(a) Mention one symptom to diagnose the sickness.
(b) What caused the sickness?
(c) How could she recover by herself after sometime?

Question 18.
How has RNAi technique help to prevent the infestation of roots into tobacco plants by nematode Meloidegyne incognitia?

Question 19.
“In a food chain, a trophic level represents a functional level, not a specie.” Explain. 3

OR

(a) Name any two places where it is essential to install electrostatic precipitators. Why is it required to do so?
(b) Mention one limitation of the electrostatic precipitator

Question 20.
Prior to a sports event, blood and urine sample of sports person are collected for drug tests.3
(a) Why is there a need to conduct such tests?
(b) Name the drugs the authorities usually look for.
(c) Write the generic names of two plants from which these drugs are obtained.

Question 21.
Describe the experiment that helped to demonstrate the semi conservative mode of DNA replication.

Question 22.
Given below is a list of six micro-organisms. State their usefulness to humans:
(a) Nucleopolyhedrovirus
(b) Saccharomycs cerebisiae
(c) Monascus purpureus
(d) Trichoderma polysporum
(e) Penicillium notatum
(f) Propionibacterium sharmanii

SECTION-D

Question 23.
Reproductive and Child Flealthcare (RCH) programme are currently in operation. One of the majof tasks of these programmes is to create awareness amongst people about the wide range of reproduction related aspects. As this is important and essential for building a reproductively healthy society.
(a) “Providing sex education in schools is one of the ways to meet this goal.” Give four points in support of your opinion regarding this statement.
(b) List any two ‘indicators’ that indicate a reproductively healthy society.

SECTION-E

Question 24.
(a) Explain the post-pollination events leading to seed production in angiosperms.
(b) List the different types of pollination depending upon the source of pollen grains.

OR

(c) Briefly explain the events of fertilisation and implantation in an adult human female.
(d) Comment on placenta as an endocrine gland.

Question 25.
(a) How are the following formed and involved in DNA packing in a nucleus of a cell? 5

• Histone octomer
• Nucleosome
• Chromatin

(b) Differentiate between Euchromatin and Heterochromatin.

OR

Explain the role of lactose as an inducer in a lac operon

Question 26.
(a) Why should we conserve biodiversity? How can we do it?
(b) Explain the importance of biodiversity hot spots and sacred groves.

OR

(a) Represent diagrammatically three kinds of age-pyramids for human populations.
(b) How does an age pyramid for human population at given point of time help the policy makers in planning for future

Answers

SECTION-A

Answer 1.

(a) Sex-linked.

(b) Haemophilia/Colourblindness.

 

Answer 2.
Identify the reason for the selection of DNA polymerase from Thermus aquaticus for Polymerase Chain Reaction.

Answer 3.
Incentives given to couples with small families/media publicity – posters of happy couples with two children (slogan-Hum Do Humare Do)/Motivate to promote smaller families by using contraceptive methods. (Any two)

Answer 4.
Thymus provides micro-environment for the development and maturation of T-lymphocytes; its degeneration will weaken the immune system so the child will be prone to frequent infections.

Answer 5.
Down’s Syndrome.
SECTION-B

Answer 6.
Pea: Flowers of pea plants are bisexual, monoecious / self pollinated (to produce pods with viable seeds.

Papaya: Dioecious plant/unisexual plant bearing male and female flowers on separate plants, unable to produce viable seeds as there is no cross pollination/it could be a male plant which is unable to produce fruit and seeds.

Answer 7.
Stop codon: does not code for any amino acid/terminates the synthesis of polypeptide chain. Unambiguous codon: one codon codes for one amino acid only
Degenerate codon: some amino acids are coded by more than one codon
Universal codon: genetic code is same for all organisms (bacteria to humans)

Answer 8.
Steps for producing disease resistant plants:

1. Screening of germplasm (for resistance sources)
2. Hybridization of selected parents !
3. Selection and evaluation of hybrids
4. Testing and release of new varieties

Answer 9.
Nucleopolyhedrovirus.
Species specific, narrow spectrum insecticidal application, no negative impact on non target organisms.

Answer 10.
UV rays act on CFC’s, release Cl atoms, which act on ozone to release O₂, resulting in ozone layer depletion/causing ozone hole.

 OR

Sacred groves are highly protected because of religious and cultural traditions, refuge for large number of rare and threatened plants/ecologically unique and biodiversity rich regions.

SECTION-C

Answer 11.
Colostrum, rich in nutrients, rich in antibodies/rich in IgA/provide passive immunity/provides :immunity to new born/helps to develop resistance in new born/readily available for new born? hygienic/develops a bond between mother and child.

Answer 12.
Sickle cell anaemia/Phenylketonuria/Thalassemia/O Blood group /Non-rolling of tongue / fused or attached ear lobes / inability to taste PTC (phenyl thiocarbamide).

Similar cross can be considered for any other trait mentioned above.

Answer 13.

Two pre sterilised flasks with killed yeast, one sealed, other open to air, differential growth of life in two flasks/life was found only in open flask. The given diagram can be considered in lieu of above explanation.
Life comes from pre-existing life (it came from air entering the flask)/proved the theory of biogenesis.

Answer 14.
Two species (Saccharum barberi and Saccharum officinarum) were crossed to get sugarcane varieties with high yield/thick stem/high sugar content/ability to-grow in North India.

Answer 15.
PCR/Polymerase Chain Reaction.
Separation/ denaturation of two strands of two dsDNA, using two sets of primers / small chemically synthesised oligonucleotides complementary to regions of DNAand (thermostable) DNA polymerase/Taq polymerase, extension of the primers, by enzyme using nucleotides replicates the DNA and if the process of replication is repeated many times, multiple copies of DNA are produced.
The following diagram can be considered in lieu of the explanation.

Answer 16.
1. Plants/bacteria/ fungi/ animals whose genes have been altered by manipulation.
2. Tolerance to abiotic stresses/like cold/drought/salt/heat, reduced reliance on chemical pesticides/pest resistant crops, reduce post harvest losses, increased efficiency of mineral usage by plants, enhanced nutritional value, to create tailor made plant.

Answer 17.
(a) Nausea/fatigue/heart palpitation
(b) Low atmospheric pressure at high altitude, body deprived of O₂.
(c) Increase in RBC, decreases binding capacity of haemoglobin, increased breathing rate, get acclimatised.

Answer 18.
Using Agrobacterium vectors, nematode specific genes introduced into host plant, produced sense antisense RNA in host cells, ds RNA – initiated RNAi, silenced specific mRNA of nematode, parasite could not survive in transgenic host.

Answer 19.
Position of a species in any trophic level is determined by the function performed by that mode of nutrition of species in a particular food chain. A given species may occupy more than one trophic level in the same ecosystem (in different food chains) at the given time. If the function of the mode of nutrition of species changes its position shall change in the trophic levels, same species can be at primary consumer level in one food chain and at secondary consumer level in another food chain in the same ecosystem at the given time.

OR

(a) Thermal power plants/smelters/ other particulate matter releasing industries.
To remove particulate matter (Any two)
(b) Very small particulate matter/less than 2.5 micrometres are not removed/velocity of air between plates must be low enough to allow the dust to fall/cannot work without electricity.

Answer 20.
(a) To detect drug abuse/use of banned drugs/use of cannabinoids/anabolic steroids/narcotic analgesic/diuretics/hormones/drugs used to accelerate performance / increase muscle strength/bulk/promote aggressiveness/to ensure fair game.
(b) Cannabinoids/cocaine/coca alkaloid / coke /crack/ hashish /charas/ganj a /hemp plant extract.
(c) Cannabis/Atropa/Erythroxylum/Datura. (Any two)

Answer 21.
Matthew Meselson and Franklin Stahl grew E.coil in ¹⁵NH₄C1 for many generations to get ¹⁵N incorporated into DNA. Then the cells are transferred into ¹⁴NH₄C1. The extracted DNA are centrifuged in CsCl and measured to get their densities, DNA extracted from the culture after one generation (20 minutes), showed intermediate hybrid density, DNA extracted after two generations (40 minutes) showed light DNA and hybrid DNA.

A correctly labelled diagrammatic representation in lieu of the above explanation of experiment to be considered.

Answer 22.
(a) As bio control agents / species specific / narrow spectrum insecticidal application / no negative impacts on plants / mammals / birds / fish / non target insects / Integrated Pest Management.
(b) Used in bread making/brewing industry/ethanol/CO, production
(c) Cholesterol lowering agent/competitively inhibiting the enzyme responsible for synthesis of cholestrol
(d) Produces cyclosporin-A/immuno suppressive agent
(e) Produces antibiotic penicillin
(f) Produces large holes in swiss cheese/products large amount of CO₂ in swiss cheese.

SECTION-D

Answer 23.
(a)

• Provide right information to the young so as to discourage children from believing in myths and
• misconception about sex related aspects.
• Proper information about reproductive organs
• Proper information about adolescence and related changes
• Safe hygienic practices
• STDs/AIDS
• Available birth control options
• Care of pregnant mothers
• Post natal care
• Importance of breast feeding
• Equal opportunities for male and female child
• Awareness of problems due to uncontrolled population growth
• Sex abuse
• Sex related crimes (Any four)

(b) Better awareness about sex related matters/increase in number of assisted deliveries/better post natal care/decrease in IMR (Infant Mortality Rate)/decrease MMR(Matemal Mortality Rate)/increase in number of couples with small families/better detection and cure of STDs/ overall increased medical facilities for sex related problems/total well being in all aspects of reproduction/physical-behavioural-social /physically and functionally normal reproductive organs/normal emotional and behavioural interaction among all sex related aspects. (Any two)

SECTION-E

Answer 24.
(a) Pollen pistil interaction, germination of pollen tube that carries two male gametes, double
fertilization / syngamy and triple fusion, development of endosperm, development of embryo, maturation of ovule into seed.
(b) Autogamy/self pollination/Geitonogamy Xenogamy/cross pollination

OR

(a) Fertilization:

• Sperm comes in contact and enters the secondary oocyte
• Activates / induces secondary oocyte to complete meiosis II leads to formation of ovum/ootid
• The haploid nucleus of sperm and that of ovum fused to form a diploid zygote completing the process of fertilization

Implantation:

• Trophoblast layer of blastocyst attaches to the endometrium (of the uterus)
• The uterine cells divide rapidly and cover the blastocyst,
• The blastocyst becomes embedded in the endometrium and the implantation is

Answer 25.
(a)
1. Eight molecules of (positively charged basic proteins called) histones are organised to form histone octamer.
2. Negatively charged DNA wrapped around positively charged histone octamer to give rise to nucleosome
3. Nucleosome constitute the repeating unit of a structure called chromatin

(b)

Euchromatin	Hetrochromatin
1. Loosely packed	1. Densely packed
2. Stains light	2. Stains dark
3. Transcriptionally active	3. Transcriptionally inactive (Any two differences)

OR

Lactose/inducer binds with repressor protein, inactivates it, frees operator gene, RNA polymerase freely move over structural genes/RNA polymerase access to the promoter, transcribing to, lac mRNA, which on translation, produce transacetylase, permease, β-galactosidase.
The following diagram to be considered in lieu of above explanation.

Answer 26.
(a)
(1) Narrowly utilitarian-related examples like derive economic benefits from nature food (cereals, pulses, fruits)/firewood/fibre/construction materials/industrial products (tannins, lubricants, dyes, resi’ns, perfumes) / product of medicinal importance/drugs.

• Broadly utilitarian — 20% of total 0₂ from Amazon forests / pollination / aesthetic pleasures.
• Ethical — millions of species (plants, animals, microbes) share this planet/we need to realise that every species has an intrinsic value (even if it may not have any economic value to us)/we have a moral duty to care for their well being and pass on our biological legacy to future generations.

(2)

• In situ conservation / biosphere reserves/ national parks / sanctuaries / sacred groves.
• Ex situ conservation/zoological parks /botanical gardens/wild life safari parks/cryopreservation/seed banks/tissue culture (eggs in vitro).

(b) Hot spots – regions with high level of species richness, high degree of endemism Sacred groves – tracts of forest containing tree/wildlife were venerated, and given total protection/to protect last refuges for a large number of rare and threatened plants.

OR

(b) Planning of health/ education/transport/ infrastructure/finance/food/employment can depend on the age-pyramid analysis of a population. (Any two explanations)

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