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 3 of Solved CBSE Sample Paper for Class 12 Biology is given below with free PDF download solutions.<\/p>\n
Time: 3 Hours<\/strong> General Instructions:<\/strong><\/p>\n SECTION-A<\/strong><\/p>\n Question 1. Question 2. Question 3. Question 4. Question 5. SECTION-B<\/strong><\/p>\n Question 6. Question 7. Question 8. Question 9. Question 10. SECTION-C<\/strong><\/p>\n Question 11. Question 12. Question 13. Question 14. Question 15. Question 16. Question 17. Question 18. Question 19. Question 20. Question 21. Question 22. SECTION-D<\/strong><\/p>\n Question 23. SECTION-E<\/strong><\/p>\n Question 24. Question 25. Question 26. Answers<\/strong><\/p>\n SECTION-A<\/strong><\/p>\n Answer 1. Answer 2. Answer 3. Answer 4. Answer 5. SECTION-B<\/strong><\/p>\n Answer 6. Answer 7. Answer 8. Answer 9. Answer 10. SECTION-C<\/strong><\/p>\n Answer 11. Answer 12. Answer 13. The process of gametogenesis (oogenesis) in females begins from the part of the brain,\u00a0(called hypothalamus) which releases a hormone called gonadotropin releasing hormone or GnRH that further stimulates the release of hormones to act on gonads.In female, Follicle stimulating hormone acts on anterior pituitary which stimulates the\u00a0folliciles present in the ovary containing the developing eggs. It also stimulates the ovary\u00a0to produce the hormone, called oestrogen. This leads to the development of secondary sexual characteristics including the development of breasts and deposition of fat in some places. It also signals a drop in FSH and the production of LH (Leutinising hormone). This LH further causes the process of ovulation (i.e. the release of the egg in the females).<\/p>\n Answer 14. Answer 15. Answer 16. Answer 17. Answer 18. (\u0430) Weather and climate change by rising temperature and melting of ice caps, glaciers worldwide OR Answer 19. Answer 20. Answer 21. Answer 22. SECTION-D<\/strong><\/p>\n Answer 23. Answer 24. An antibody is represented as H2<\/sub>I2<\/sub> molecule. In our body, different type of antibodies are produced such as IgA, IgM, IgE, IgG. All these antibodies are found in blood. Most prevalent class of antibody 75-80% of total antibody. Protects against fungi, bacteria, toxins, etc.<\/p>\n It can cross placenta from mother to child and provides immune protection to newborns.<\/p>\n Responsible for Rh factor in blood.<\/p>\n<\/td>\n<\/tr>\n Third most common antibody.<\/p>\n If constitutes 5-10% total antibodies.<\/p>\n They are first to be produced in response to encounter with a pathogen.<\/p>\n Responsible for blood transfusion reactions in ABO blood system.<\/p>\n<\/td>\n<\/tr>\n Second most prevalent antibody.<\/p>\n It is about 15% of the total antibodies.<\/p>\n Secreted through parts lined by mucous system.<\/p>\n Found in secretions from nose, eyes, lungs and digestive tract, saliva, tears, etc.<\/p>\n Also found in colostrum, i.e., breast milk for newborns for immune protection.<\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n OR<\/strong> Answer 25. An antibody is represented as H2<\/sub>I2<\/sub> molecule. In our body, different type of antibodies are produced such as IgA, IgM, IgE, IgG. All these antibodies are found in blood. Most prevalent class of antibody 75-.80% of total antibody. Protects against fungi, bacteria, toxins, etc.<\/p>\n It can cross placenta from mother to child and provides immune protection to newborns.<\/p>\n Responsible for Rh factor in blood.<\/p>\n<\/td>\n<\/tr>\n Third most common antibody.<\/p>\n If constitutes 5-10% total antibodies.<\/p>\n They are first to be produced in response to encounter with a pathogen.<\/p>\n Responsible for blood transfusion reactions in ABO blood system.<\/p>\n<\/td>\n<\/tr>\n Second most prevalent antibody.<\/p>\n It is about 15% of the total antibodies.<\/p>\n Secreted through parts lined by mucous system.<\/p>\n Found in secretions from nose, eyes, lungs and digestive tract, saliva, tears, etc.<\/p>\n Also found in colostrum, i.e., breast milk for newborns for immune protection.<\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Answer 26. (2) The amount of energy flow in an ecosystem decreases with successive tropic levels as only 10% of energy gets transferred from one trophic level to next successive level. The energy lasts in the form of respiration and other important activities for maintaining life. If more trophic levels are present, the residual energy will be limited and decreases to such an extend that it cannot further support any trophic level by the energy flow. Thus, it is rightly said that the food chain is generally limited to the 3-4 trophic levels only. We hope the CBSE Sample Papers for Class 12 Biology Paper 3 help you. If you have any query regarding CBSE Sample Papers for Class 12 Biology Paper 3, drop a comment below and we will get back to you at the earliest.<\/p>\n","protected":false},"excerpt":{"rendered":" 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 3. CBSE Sample Papers for Class 12\u00a0 Biology Paper 3 Board CBSE Class XII Subject Biology Sample Paper Set Paper 3 Category CBSE Sample Papers Students who are going to […]<\/p>\n","protected":false},"author":7,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_genesis_hide_title":false,"_genesis_hide_breadcrumbs":false,"_genesis_hide_singular_image":false,"_genesis_hide_footer_widgets":false,"_genesis_custom_body_class":"","_genesis_custom_post_class":"","_genesis_layout":"","footnotes":""},"categories":[6805],"tags":[],"yoast_head":"\n
\nMaximum Marks: 100
\n<\/strong><\/p>\n\n
\nCross hybridization among the selected parents during any plant breeding programme is meant to be a tedious and a time consuming process. Why?<\/p>\n
\nIn which phenomenon, a phenotype of the Fj hybrid offspring does not resemble any of the parent and is intermediate between the expression of two alleles?<\/p>\n
\nIt is often seen that replication of DNAdoes not initiate randomly anywhere in DNA, it instead begins at definite regions. Why is it so? Give reason.<\/p>\n
\nList two advantages of inbreeding in animals.<\/p>\n
\nProduction of antibiotics has been widespread by the pioneering efforts of which two scientists?<\/p>\n
\nHow is diapause different from hibernation?<\/p>\n
\nWhat are the two major aims and objectives behind the reproductive child healthcare programmes?
\nOR
\n<\/strong>Human Placenta acts as a structural and functional unit between a foetus and maternal body.\u00a0Justify the statement giving any two basic functions it performs.<\/p>\n
\nIn what way does the cell mediated system works in a body when it gets infected?<\/p>\n
\nBoth linear DNA and plasmid DNA of same length having one site for a restriction endonuclease are cut and separated on agarose gel electrophoresis. The plasmid DNA shows one DNA band, while a linear DNA shows two fragments. State the reason behind the fact.<\/p>\n
\nMention two functions of DNA polymerase.<\/p>\n
\nCo-dominance acts as the phenomenon of resemblance of off springs to both the parents. Justify the statement with the support of a well known example.<\/p>\n
\nStudents while performing the experiment were given two different vectors in two different bacterial colonies being cultured in a chromogenic substrate. They observed that the bacterial colonies with cloning vector A were colourless while those with coloning vector B were blue in colour. Explain the phenomenon and the procedure behind the fact that the students were trying to figure out.<\/p>\n
\nGametogenesis is the phenomenon known for the formation of haploid gametes taking place in both males and females. Observe the flowchart given below highlighting the influence of process of gametogenesis and answer the questions that follows.
\n![\"CBSE](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2018\/12\/CBSE-Sample-Papers-for-Class-12-Biology-Paper-3.1.png\")
\n(1) Identify the type of gametogenesis shown and in whom does it take place?
\n(2) Explain the role of different hormones involved in the complete process<\/p>\n
\nIf during the formation of male gametes, each pollen grain produces two male gametes. Then, deduce the number of pollen grains which would be required to fertilise five ovules present in a particular carpel. Give reasons to support your answer.<\/p>\n
\nMechanism of sex determination differentiates from one another in every living beings. Describe in detail about such mechanism in case of humans, birds and grasshoppers respectively<\/p>\n
\nIt is known that Global carbon in the biosphere is fixed through the process of photosynthesis.Explain how is it done and also mention the ways by which carbon is eventually returned to the atmosphere?<\/p>\n
\nIn what ways the biocontrol microbes controls their target species through a web of biological interactions? Explain giving some important examples.<\/p>\n
\nIt has been recorded that the temperature of the earth\u2019s atmosphere has increased 0.6\u00b0C.
\n(1) What has caused this increase?
\n(2) Explain its consequences.
\nOR
\n<\/strong>Due to uncontrolled excessive hunting, the population of tigers in a forest has become zero. Discuss the long-term effects of this situation on the population of deer in that forest.<\/p>\n
\n(1) What happens when Meloidegyne incognitia consumes cells with RNAi gene?
\n(2) How agrobacterium vectors are also proved useful in genetic engineering?<\/p>\n
\nAjay went with his father to see this friend in the hospital. They saw that doctor there was advising Ajay’s friend about the personal hygiene. What according to you is the importance of personal hygiene? List any six measures every person or a society should follow to prevent diseases from spreading by contaminated food and water.<\/p>\n
\nGive reasons for the following:
\n(1) Competition between intraspecific species tend to be more intense than the interspecific species.
\n(2) Lichens show obligate mutualism.
\n(3) Population of different species are not capable of breeding with each other.<\/p>\n
\nWith the help of a flowchart, show the process by which the genetic information from one strand of DNA is copied in to RNA in case of prokaryotes.<\/p>\n
\nWhile having lunch in canteen, Prateek was discussing with his friends about the movie in which the hero used to donate his sperms to help the couples undergoing infertility. Listening this one of Prateek\u2019s friend argued against such thing and said that this type of activity and movies are just to earn money and they should be banned.Discuss four points with appropriate23.explanation how Prateek will make him understand that helping out couples in such a way is not incorrect.<\/p>\n
\nWhat do you understand by the term \u2018antibodies\u2019 in our body? Explain in detail about the different types and roles of antibodies.
\nOR<\/strong>
\nDrugs like LSD, barbiturates, amphetamines, etc. are used as medicines to help patients with mental illness. However, excessive doses and abusive usage are harmful. Enumerate the major adverse effects of such drugs in humans.<\/p>\n
\n(1) Define the term antibody. Highlight the structural importance of antibody molecule.
\n(2) Name different types of antibodies found in the blood, mentioning the functions of each.<\/p>\n
\n(1) It has been seen since a long time that different organisms and their population are connected to each other through a special connection. Identify that connection and write about its different types.
\n(2) Length of a food chain within an ecosystem generally limited to 3-4 trophic levels. Justify.<\/p>\n
\nThis is because cross hybridization as a step in a plant breeding programme involves a collection of pollen grains from the desired plants and other pollination techniques to incorporate the desired traits.<\/p>\n
\nIncomplete Dominance.<\/p>\n
\nReplication of DNA molecule begins at a definite region called Ori or (origin of replication) because it is this site which binds the pre-replication complex or a protein complex that recognizes, unwinds and begins to copy DNA.<\/p>\n
\nAdvantages of inbreeding in animals are
\n<\/span><\/strong>(1)\u00a0 Necessary in evolving a pure line in any animal breed.
\n<\/span>(2) Increases homozygosity<\/span><\/p>\n
\nErnest Chain and Howard Florey have made the production of antibiotics widespread by pioneering efforts.<\/p>\n
\nHibernation is the phenomenon commonly depicted by cold-blooded animals, which escape cold by hiding themselves in shelters such as burrows muds, etc revealing minimum , physiological activity. It is performed by large animals while, on the other hand, diapause is a\u00a0stage of suspended development which takes place during unfavourable conditions like stress,\u00a0etc. The growth and development gets resumed on the return of favourable conditions. This is usually performed by microscopic or very small organisms like zooplanktons etc.<\/p>\n
\nWhat are the two major aims and objectives behind the reproductive child healthcare programmes?
\nOR
\n<\/strong>Human Placenta acts as a structural and functional unit between a foetus and maternal body.Justify the statement giving any two basic functions it performs.<\/p>\n
\nIn what way does the cell mediated system works in a body when it gets infected?<\/p>\n
\nBoth linear DNA and plasmid DNA of same length having one site for a restriction endonuclease are cut and separated on agarose gel electrophoresis. The plasmid DNA shows one DNA band, while a linear DNA shows two fragments. State the reason behind the fact<\/p>\n
\nTwo functions of DNA polymerase are\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/strong>
\n(1) It adds nucleotides to the DNA and removes RNA primer from DNA.
\n(2) It also proofreads the created portion of DNA<\/p>\n
\nCo-dominance is the phenomenon in which two alleles expressed themselves independently when present in a single organism, i.e. they neither show dominant recessive relationship nor they show an intermediate condition. Thus, it is true to say that co-dominance acts as the phenomenon of resemblance of offspring to both the parents.
\nFor example,<\/strong> ABO blood grouping in humans beings.
\nThe four phenotypes to blood groups in humans, \u2018A\u2019, \u2018B\u2019, \u2018AB\u2019, \u2018O\u2019 are produced by the three different alleles i.e. IA<\/sup>, IB<\/sup> and i of the immunogene.
\nThe alleles IA<\/sup> and IB<\/sup> are completely dominant over \u2018i\u2019 an allele, which means that when IA<\/sup> and i are present in an individual only IA<\/sup> expresses and on the other hand when IB<\/sup> and i are present only IB<\/sup> will express, as an allele i does not produce any sugar.
\nBut eventually in the case, where an individual possesses both IA<\/sup> and IB<\/sup>, both the alleles expresses their own types of antigens and the person is said to be having any of the blood group as mentioned below. This is because alleles IA<\/sup> and IB<\/sup> are co-dominant with each other.
\n![\"CBSE](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2018\/12\/CBSE-Sample-Papers-for-Class-12-Biology-Paper-3.2.png\")
<\/p>\n
\nStudents were working to differentiate recombinants and non-recombinants DNA on the basis of production of colour in the presence of a chromogenic substrate.
\nDuring this phenomenon, a recombinant DNA is inserted within the coding sequence of an enzyme 1-galactosidase that results in an inaction of the enzyme. Due to which, the bacterial colonies having plasmid inserted within it shows no colouration at all and those without plasmid tends to show blue colour.<\/p>\n
\n(1) The process shown in the figure above is oogenesis. It is a type of gametogenesis which occurs in females.
\n(2) The hormones involved in the process of oogenesis in females similar to those involved in the process of spermatogenesis in males with a only difference, that is, oogenesis hormones acts on ovaries to stimulate the complete process.<\/p>\n
\nEach pollen grain generates to produce two male gametes that are carried through a pollen tube to the embryo sac. This pollen tube enters the embryo sac through the filliform apparatus of one of the synergids present at the micropylar end and releases two male gametes.Out of these two male gametes, one fuses with the egg cell while, the other fuses with the\u00a0 secondary nucleus. Therefore, one pollen grain can fertilise only one ovule. Therefore, in order\u00a0to process fertilisation of five ovules, five pollen grains will be required.<\/p>\n
\nSex determination mechanism in humans, birds and grasshopper are as follows:<\/strong>
\n\u00a0(1) Humans:<\/strong> In case of human beings, females have homogametic (XX) and males have heterogametic (XY) sex chromosome. Hence, in this case, the sperm is responsible for the determination of sex of the offspring.
\n(2) Birds:<\/strong> In case of birds, females have heterogametic (ZW) and males have homogametic
\n(ZZ) sex chromosomes. Hence, egg is responsible for the sex determination of the offspring,
\n(3) Grasshopper:<\/strong> These show XO type of sex determination. Some species of grasshoppers\u00a0bears X-chromosome while, others do not have sex chromosome. The female have homogametic (XX) and the male have heterogametic (XO) sex chromosome.<\/p>\n
\nThe CO2<\/sub> is added to the atmosphere mainly by burning of the fossil fuels, volcanic activities and by the process of respiration. Decomposers also contribute substantially to CO2<\/sub> pool by their processing of waste materials and dead organic matter of land and oceans.
\nAbout 4 x 1013<\/sup> kg of carbon is fixed annually in the biosphere through photosynthesis.<\/p>\n
\nBiological control refers to the use of biological methods for controlling plant diseases, pests and weeds etc.
\nSome examples of biological controls are:
\n<\/strong>(1) Ladybird and dragonfly are used to get rid of aphids and mosquitoes respectively.
\n(2) Bacillus thuringiensis is used for the control of butterfly caterpillar.
\n(3) Fungus species Trichoderma are used in controlling infection in roots.
\n(4) Baculoviruses are used as narrow spectrum insecticidal applications<\/p>\n
\n(1) Increase in atmospheric concentration of greenhouse gases (CO2<\/sub>) has resulted in the rise of atmospheric temperature by 0.6\u00b0C (global warming).
\n(2) Consequences for the increase in temperature are<\/p>\n
\n(b)\u00a0\u00a0 Rise in water levels of seas and oceans.
\n(c) Affects food production.
\n(d) Sudden changes in rainfall pattern and occurrence of frequent floods, droughts, hurricanes.<\/p>\n
\n<\/strong>If the number of predators (tigers) get reduced, the number of prey (deer) population will increase which will increase the pressure on the vegetation. As a result, plant population will decrease due to overgrazing. Little vegetation puts pressure on deer population and as a result deer population will decrease due to starvation, death or migration. Thus, ultimately the tigers (predators) will be affected.<\/p>\n
\n(1) If Meloidegyne incognitia consume cells with RNAi gene, silencing of specific mRNA occurs due to a complimentary dsRNA molecule formation which binds and prevents translation of mRNA (silencing) thus, causing death of the nematode.
\n(2) Agrobacterium vectors are used for the introduction of nematode-specific genes into the host plant by producing both sense and antisense RNA into host cells. As these two RNA\u2019s are complementary to each other, they form dsRNA and initiates silencing the specific mRNA of the nematode.<\/p>\n
\nPreventive measures for diseases spread by contaminated food and water are
\n(1) Proper disposal of water and excreta.
\n(2) Cleaning and disinfection of pools, water tanks and other water reservoirs.
\n(3) Storing raw and the cooked food separately.
\n(4) Cooking food in clean water and keeping it at safe temperature.
\n(5) Body should be clean, nails and hairs should be cut regularly
\n(6) Hygienic practice should be adopted at hotels and restaurants<\/p>\n
\n(1) Intraspecific competition is more intense because the requirements of individuals of same species are very similar.
\n(2) Lichens set a good example of obligate mutualism because of the naturalistic relationship between the fungi and algae or cyanobacteria in which an algae prepares food, while the fungus helps in the absorption of nutrients and provide protection.
\n(3) Different species in a population are unable to breed with each other because of various types of biological and physical barriers.<\/p>\n
\n![\"CBSE](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2018\/12\/CBSE-Sample-Papers-for-Class-12-Biology-Paper-3.3.png\")
<\/p>\n
\nPrateek will share following points with his friend in the support of the discussion.<\/p>\n\n
\n(1) Antibody is a type of a protein molecule produced by B-Lymphocytes in response to pathogens present in our blood to fight with them. T-Cells do not secrete antibodies directly however, they help B-Cells to produce them. Each antibody molecule has four peptide chains. Out of the four chains two small chains are called light (landa) chains and two large chains are called heavy (H) chains.<\/p>\n
\n![\"CBSE](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2018\/12\/CBSE-Sample-Papers-for-Class-12-Biology-Paper-3.4.png\")
<\/p>\n\n\n
\n Types of Antibodies<\/strong><\/td>\n Functions<\/strong><\/td>\n<\/tr>\n \n IgG<\/td>\n \n \n IgM<\/td>\n \n \n IgA<\/td>\n \n
\nHarmful effects of drugs like LSD, barbiturates, amphetamines etc are:<\/strong><\/p>\n\n
\n(1) Antibody is a type of a protein molecule produced by B-Lymphocytes in response to pathogens present in our blood to fight with them. T-Cells do not secrete antibodies directly. However, they help
\nB-Cells to produce them. Each antibody molecule has four peptide chains. Out of the four chains, two small chains are called light (landa) chains and two large chains are called heavy (H) chains.<\/p>\n
\n![\"CBSE](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2018\/12\/CBSE-Sample-Papers-for-Class-12-Biology-Paper-3.5.png\")
<\/p>\n\n\n
\n Types of Antibodies<\/strong><\/td>\n Functions<\/strong><\/td>\n<\/tr>\n \n IgG<\/td>\n \n \n IgM<\/td>\n \n \n IgA<\/td>\n \n
\n(1) Different organisms or population of an ecosystem are connected to each through a sequence or a series of connection called food chain. Through this chain the food and its contained energy is passed as a food of a later member of a sequence. It is actually known as a feeding chain of organisms in an ecosystem.
\nThere are mainly two types of food chains in the ecosystem:<\/strong><\/p>\n\n
\nFor example,
\n![\"CBSE](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2018\/12\/CBSE-Sample-Papers-for-Class-12-Biology-Paper-3.6.png\")
\n<\/strong><\/p>\n