CBSE Class 12 Biology 2026
289 questions · 558 marks · every one with the board’s own marking-scheme answer.
Marks by chapter
Counted from the 289 questions listed below, as the 2026 papers print them. CBSE allocates marks per unit, not per chapter — this is what was observed, not an official CBSE weightage. Every year compared →
| Chapter | Marks | Share |
|---|---|---|
| Molecular Basis of Inheritance32 questions | 72 | 12.9% |
| Human Health and Disease30 questions | 61 | 10.9% |
| Human Reproduction28 questions | 58 | 10.4% |
| Biotechnology : Principles and Processes28 questions | 57 | 10.2% |
| Principles of Inheritance and Variation28 questions | 55 | 9.9% |
| Sexual Reproduction in Flowering Plants25 questions | 55 | 9.9% |
| Evolution25 questions | 40 | 7.2% |
| Microbes in Human Welfare22 questions | 38 | 6.8% |
| Biotechnology and its Applications17 questions | 31 | 5.6% |
| Biodiversity and Conservation16 questions | 26 | 4.7% |
| Ecosystem17 questions | 24 | 4.3% |
| Organisms and Populations10 questions | 22 | 3.9% |
| Reproductive Health11 questions | 19 | 3.4% |
289 questions from 2026
- Q1Choose the option that gives the correct number of pollen grains that will be formed after 325 microspore mother cells…1 mkasked 2×
- Q1In a human, the average gene consists of (i) bases and the largest known human gene contains (ii) bases. Select the…1 mk
- Q1Foetal ejection reflex in human female triggers the release of which hormone?1 mk
- Q1Perisperm present in seed of black pepper is remnant of1 mk
- Q1Identify the parts P, Q, R, S in the figure given below and select the option in the correct order.1 mk
- Q1Which of the following groups of cells in the male gonad represent haploid cells?1 mk
- Q1To separate repetitive DNA from bulk genomic DNA, which of the following method is used?1 mk
- Q1Caenorhabditis elegans is a nematode which is1 mk
- Q1Which part of the ovule hardens to form seed coat of a seed?1 mk
- Q1Identify the plant in which emasculation is not required for artificial hybridization.1 mk
- Q2Observe the contents 1, 2, 3 and 4 of soil samples I, II and III shown in the graph. If the temperature and moisture of…1 mk
- Q2Which of the following is a carrier for the disease Amoebiasis?1 mk
- Q2Microbes commonly used in kitchen are1 mk
- Q2The cells of endosperm have 24 chromosomes. What will be the number of chromosomes in the gametes?1 mk
- Q2Which one of the following statements is correct?1 mk
- Q2Which of the following is not a functional unit of an ecosystem?1 mk
- Q2Filiform apparatus in the embryo sac of an angiosperm is present at the micropylar tip of:1 mk
- Q2Which of the following is not a component of immune system?1 mk
- Q2Interferons are most effective in making non-infected cells resistant against the spread of which of the following…1 mk
- Q2Select the correct option:1 mk
- Q2The foetal ejection reflex in human triggers the release of hormone from. Fill in the blanks by choosing right option.1 mk
- Q2Self-incompatibility in some flowering plants is a mechanism that prevents self-fertilization. Fill in the blank with…1 mk
- Q2Select the phase of menstrual cycle in which the remaining parts of Graafian follicle transform into the corpus luteum.1 mk
- Q2Match the IUDs in Column I with suitable example in Column II.1 mk
- Q3Which of the following traits studied by Mendel in pea plant is a recessive trait?1 mk
- Q3What does I in restriction enzyme Hind S_2 I indicate?1 mk
- Q3During different phases of menstrual cycle, hormones are secreted. Choose the option showing the correct sequence of…1 mk
- Q3A female undergoing IVF treatment has blocked fallopian tube. The technique by which the embryo with more than 8…1 mk
- Q3A DNA molecule is 160 base pairs long. It has 30 % Guanine. How many Adenine bases are present in this DNA molecule?1 mk
- Q3In a dihybrid cross, 2400 individuals are produced in F_2 generation. Approximately how many will be phenotypically…1 mk
- Q3Match Column I with Column II and select the correct option:1 mk
- Q3A woman having genes for haemophilia on one X chromosome and a gene for colour blindness on another X chromosome…1 mk
- Q3Select the option that shows correct statements: (i) Corpus luteum secretes progesterone. (ii) Only FSH attains a peak…1 mk
- Q3A man is found to have a sperm count of less than 20 million/mL and his wife is diagnosed with blockage in the oviduct.…1 mk
- Q3The features of some structures of human male reproductive system are given below. Choose the correct option that…1 mk
- Q4Exploration of molecular, genetic and species level diversity for gaining products of economic importance is called1 mk
- Q4Select the mismatched pair:1 mk
- Q4In Pisum sativum, the flower colour may be violet (V) or white (v). What proportion of the offspring in a cross of 'VV'…1 mk
- Q4The first movements of the foetus and appearance of hair on its head are usually observed during which month of…1 mk
- Q4What could be the reason of extinction of Abingdon Tortoise from Galapagos Islands?1 mk
- Q4Which of the following is an important parameter for assessing the impact of any biotic or abiotic factor on population…1 mk
- Q4Which of the following amino acid substitutions is responsible for causing sickle cell anemia?1 mk
- Q4Golden rice is a promising transgenic crop. When released for cultivation, it will help in:1 mk
- Q4Consider the following statements and choose the correct option: Statement I: Using vaccination and immunization…1 mk
- Q4Select the correct statement. All genes located on the same chromosome:1 mk
- Q5If a sperm nucleus is injected into an oocyte then all of the following events are bypassed except -1 mk
- Q5Thorns of Bougainvillea and tendrils of Cucurbita are examples of:1 mk
- Q5Pomato was produced by fusing protoplasts of1 mk
- Q5In a human female, menstrual cycle of 28 days is represented by the diagram given below. Select the correct statement…1 mk
- Q5If a genetic disease is transferred from a phenotypically normal but carrier female to only some of the male progeny,…1 mk
- Q5Taylor and colleagues performed an experiment on which of the following organisms to provide proof for…1 mk
- Q5What conclusion can be drawn if the forelimbs of an aquatic animal and a terrestrial animal have similar anatomical…1 mk
- Q5Choose the correct statements: (i) Polycistronic mRNA is generally found in eukaryotes. (ii) The RNA polymerase II…1 mk
- Q5Four different transcription units are shown below. Choose the option with the correct image.1 mk
- Q6Appearance of antibiotic-resistant bacteria is an example of evolution due to:1 mk
- Q6In an ecosystem, different species occupy different levels and vertical distribution of species is found. This is…1 mk
- Q6What would be the minimum possibility of a dominant trait being expressed in an offspring after a monohybrid test cross?1 mk
- Q6Name the extinct ancestor of humans who ate only fruits and hunted with stone weapons.1 mk
- Q6If A= species richness and B= Endemism then biodiversity hotspots have1 mk
- Q6Internal bleeding, muscular pain, blockage of the intestinal passage and anaemia are some of the symptoms caused due to…1 mk
- Q6S is the stimulant of central nervous system and interferes with the transport of T, a neurotransmitter. Identify S and…1 mk
- Q6How many of the following features are related to Nirodh-a popular brand of condoms? (i) Prevention of sexually…1 mk
- Q6Which of the following is not a component of detritus food chain?1 mk
- Q6Arrange the following in the correct sequence of their evolution and select the correct option: (i) Seaweed (ii)…1 mk
- Q6Current percentage of tropical rainforests covering the Earth's land surface is1 mk
- Q7A bacterium having radioactive thymidine in its DNA is allowed to multiply in a medium having non-radioactive thymidine…1 mk
- Q7Identify the statements that correctly describe Darwin's Theory of Evolution. (i) Overproduction of organisms leads to…1 mk
- Q7Which of the following sacred groves is found in Meghalaya?1 mk
- Q7A doctor identifies symptoms of nasal congestion, headache, sore throat, hoarseness and cough in a patient. The…1 mk
- Q7Two plants whose DNA has been sequenced are1 mk
- Q7Some cyanobacteria in aquatic and terrestrial environment that enrich the soil by fixing nitrogen are:1 mk
- Q7Nicotine affects blood pressure and heart rate due to release of certain adrenal hormones. Following are some of the…1 mk
- Q7Monascus purpureus is a yeast used commercially in the production of which one of the following?1 mk
- Q7Study the given pedigree and identify the disease represented.1 mk
- Q8Which one of the following evidences does not support Darwin's theory of natural selection?1 mk
- Q8Which type of selection is industrial melanism observed in moth, Biston betularia?1 mk
- Q8What is the role of histamine released by mast cells?1 mk
- Q8Microbes used for biocontrol of pest butterfly caterpillars is:1 mk
- Q8Which cells are responsible for producing antibodies in a human body?1 mk
- Q8Given below is the restriction site of a restriction endonuclease Pst I and the cleavage sites on a DNA molecule. 5^′…1 mk
- Q8Which of the following is not a symptom of Ascariasis?1 mk
- Q8Antivenom injection is an example of1 mk
- Q9The given diagram shows the skulls of two different mammals. Which of the following options accurately describes the…1 mk
- Q9Expression of a particular gene helps to identify transformants. What is this gene known as?1 mk
- Q9Which of the following is a secondary consumer?1 mk
- Q9Bacillus thuringiensis is used to control which one of the following pathogens/pests?1 mk
- Q9Match Column-I with Column-II and choose the correct option:1 mk
- Q9Every trophic level has a certain mass of living material at a particular time. What is it called?1 mk
- Q9Which of the following is used to visualize DNA bands under UV light after gel electrophoresis?1 mk
- Q9Choose a correct option that shows an interaction in which one species benefits while the other is neither harmed nor…1 mk
- Q9Elution means:1 mk
- Q9Match the items given in Column I with Column II and select the correct option.1 mk
- Q9C-peptide of human insulin is:1 mk
- Q10The smallest part of DNA molecule that can be changed by point mutation is:1 mk
- Q10Given below are stages of embryo sac formation from megaspore mother cell. Identify the correct option for the cell…1 mk
- Q10The recombinant protein obtained from transgenic animals that could be used to treat emphysema is:1 mk
- Q10Messelson and Stahl's experiment carried out centrifugation in CsCl_2 density gradient to separate:1 mk
- Q10Transgenic animals have their genetic material manipulated. Select the correct option in reference to transgenic…1 mk
- Q10In RNAi, genes are silenced using which of the following biomolecules?1 mk
- Q10Which of the following ecosystem is most productive in terms of net primary productivity?1 mk
- Q10A gene having non-coding introns and coding exons is known as:1 mk
- Q10A DNA molecule is 140 base pairs long. It has 20 % thymine. How many guanine bases are present in the molecule?1 mk
- Q10The idea of use and disuse of organs for evolution of organism was proposed by1 mk
- Q10In pBR322, tetracycline, resistance gene (tet ^R ) has recognition site for which of the following restriction…1 mk
- Q11Select the odd option in the context of convergent evolution.1 mk
- Q11Which one of the following is not a component required for Polymerase Chain Reaction (PCR)?1 mk
- Q11Connell's elegant field experiments on the rocky seacoast of Scotland, found that larger barnacles Balanus dominated…1 mk
- Q11The construction of the first recombinant DNA was done by using the native plasmid of:1 mk
- Q11Genetically modified tobacco plants were produced using Agrobacterium vectors. Which property of Agrobacterium helps in…1 mk
- Q11Which of the following statements about plasmids is incorrect?1 mk
- Q11Bt-toxin genes have been expressed in plants in order to provide resistance against: (i) lepidopterans and fungi (ii)…1 mk
- Q11If any organ fails to function satisfactorily, transplantation is the only remedy to enable the patient to live a…1 mk
- Q11Some statements regarding drugs and alcohol are given below: (i) Adolescents are more vulnerable to peer pressure. (ii)…1 mk
- Q12In the following figure, two ways of pairing of two homologous pairs of chromosomes are shown. Which of the following…1 mk
- Q12Protein encoded by gene Cry-I Ab controls the infestation of which of the following?1 mk
- Q12The biomass available in plants for consumption by herbivores and decomposers, is called:1 mk
- Q12Which connective tissue connects ovary to pelvic wall and uterus?1 mk
- Q12Cattle or goats are never seen browsing on the weed, Calotropis. Select the correct option for the reason.1 mk
- Q12According to IUCN, some of the extinctions include: (i) Dodo (ii) Indian gazelle (iii) Thylacine (iv) Steller's Sea Cow…1 mk
- Q12Which of the following fish led to the extinction of an ecologically unique assemblage of more than 200 species of…1 mk
- Q12The method of contraception that is hormone-based and prevents ovulation is:1 mk
- Q12Select the correct option for the pair of plants pollinated by water.1 mk
- Q13Assertion: Activated sludge contains large population of bacteria. Reason (R): These bacteria help in anaerobic…1 mk
- Q13Assertion: Genetically modified microbes help in crop protection. Reason (R): Bacillus thuringiensis (Bt) bacteria…1 mk
- Q13Assertion: Apomixis leads to production of genetically identical off- springs. Reason (R): Apomixis involves…1 mk
- Q13Assertion: When we see stars, we are apparently peeping into the past. Reason (R): What we see today is an object whose…1 mk
- Q13Assertion: After implantation, finger-like projections appear on the trophoblast called chorionic villi. Reason (R):…1 mk
- Q13Assertion: Cleistogamous flowers have assured seed set. Reason (R): Cleistogamous flowers are invariably autogamous and…1 mk
- Q13Assertion: The embryo with 8 to 16 blastomeres is called a morula. Reason (R): The morula continues to divide and…1 mk
- Q13Assertion: The population of melanized moths increased in industrial areas after Industrial Revolution. Reason (R): In…1 mk
- Q13Assertion: Pollen grains have a mucilaginous covering on them in most of the water pollinating plants. Reason (R):…1 mk
- Q13Assertion: Fossils provide direct evidence for evolution. Reason (R): Fossils help to trace evolutionary relationships…1 mk
- Q14Assertion: Repetitive sequences make up a very large portion of human genome. Reason (R): Repetitive sequences do not…1 mk
- Q14Assertion: The milk produced by transgenic cow 'Rosie' was nutritionally more balanced product for human babies than…1 mk
- Q14Assertion: Nucleopolyhedrovirus are useful, as they are good biological control agents. Reason (R): They are…1 mk
- Q14Assertion: The human blood group 'AB' exemplifies co-dominance. Reason (R): The gene for human blood group trait exists…1 mk
- Q14Assertion: Microbes are used for commercial production of alcohol and beverages. Reason (R): Yeast converts glucose…1 mk
- Q14Assertion: Ecosystems require a constant supply of energy to synthesize the molecules they require. Reason (R): This is…1 mk
- Q14Assertion: Net Primary Productivity (NPP) is always less than Gross Primary Productivity (GPP). Reason (R): A portion…1 mk
- Q14Assertion: The interaction between a whale and the small barnacles on its back is considered as commensalism. Reason…1 mk
- Q15Assertion: Under a particular set of selection pressure, organisms evolve towards the most efficient reproductive…1 mk
- Q15Assertion: Flocs are masses of bacteria associated with fungal filaments in secondary treatment of sewage. Reason (R):…1 mk
- Q15Assertion: Nucleopolyhedrovirus are useful as they are good biocontrol agents. Reason (R): They are species-specific,…1 mk
- Q15Assertion: The endometrium undergoes cyclic changes during the menstrual cycle. Reason (R): Perimetrium contracts…1 mk
- Q15Assertion: Trichoderma species are free living fungi that are very common in the root ecosystems. Reason (R): They are…1 mk
- Q15Assertion: DNA cannot pass through cell membrane of a bacterial cell. Reason (R): DNA is a hydrophilic molecule.1 mk
- Q15Assertion: IUCN Red List helps in identifying and protecting endangered species worldwide. Reason (R): The list…1 mk
- Q16Assertion: Repetitive sequences are stretches of DNA sequences that are thought to have no direct coding functions.…1 mk
- Q16Assertion: Besides curdling of milk, LAB also improves its nutritional quality by increasing Vitamin B12. Reason (R):…1 mk
- Q16Assertion: DNA Ligase is used to join DNA fragments. Reason (R): It catalyses the formation of glycosidic bonds between…1 mk
- Q16Assertion: In terrestrial ecosystem much larger fraction of energy flows through grazing food chain. Reason (R):…1 mk
- Q16Assertion: The pyramid of biomass in a pond aquatic ecosystem is always inverted. Reason (R): The biomass of consumers…1 mk
- Q16Assertion: The use of chitinase enzyme is necessary for the separation of DNA from yeast cells but not in the case of…1 mk
- Q16Assertion: Hardy-Weinberg principle says that allele frequencies in a population are stable. Reason (R): Hardy-Weinberg…1 mk
- Q17A health officer visiting two different regions reported the following symptoms in patients: Region A - Sustained high…2 mk
- Q17Is it possible for a trait to be inherited by an organism but not expressed in its phenotype? Justify and illustrate…2 mk
- Q17Mention the sites of action of the hormones 'GnRH' and 'FSH' during spermatogenesis. Write one function of each of…2 mk
- Q17The diagram below shows the sequence of amino acids in part of haemoglobin molecule. (i) If the base * T is substituted…2 mk
- Q17How do 'implants' act as an effective method of contraception in human females? Mention one advantage of implants over…2 mk
- Q17Define Humoral immune response. Name any two types of antibodies found to give humoral immune response in humans.2 mk
- Q17State the role of thymus as a lymphoid organ. Name the cells that are released from it and mention their functions.2 mk
- Q17Draw a labelled diagram of the embryonic stage that gets implanted in the human uterus. State the functions of two…2 mk
- Q17A person complains of persistent itching in the groin region and scalp. The person also shows dry and scaly lesions on…2 mk
- Q17What is the role of LAB (Lactic Acid Bacteria) in preparation of curd? Mention two health benefits of consuming curd.2 mk
- Q17A patient reports a high fever, chills and sweating. His blood shows the presence of a toxic substance. (i) Identify…2 mk
- Q17Mention the functions of each of the following: (i) Tassels of Corn Cob (ii) Scutellum OR Farmers prefer apomictic…2 mk
- Q18(i) Rearrange the following in correct order of their appearance on Earth between 2 million years and 40,000 years ago:…2 mk
- Q18Identify a, b, c and d in the following table with reference to birth control.2 mk
- Q18Briefly describe the process of DNA extraction from a fungal cell. Name the chemicals used in the process.2 mk
- Q18How do scientists use microinjection and gene gun in biotechnology?2 mk
- Q18A patent with Type I diabetes is unable to produce sufficient insulin. How has recombinant DNA technology helped in…2 mk
- Q18Name the muscular and glandular layers of female uterus. Mention one function of each. OR (i) Why are STI (Sexually…2 mk
- Q18(i) How does a farmer use dormancy of seed to his advantage? (ii) Differentiate between pea seed and castor seed. OR…2 mk
- Q18(i) Mention any two characteristics of Neanderthal man that lived near East and Central Asia. (ii) Identify the…2 mk
- Q18Write one way by which apomictic seeds can be developed. Why do farmers prefer apomictic seeds over hybrid seeds?2 mk
- Q18Explain the mutually rewarding relationship between Yucca plant and species of moth. OR Pollination success will be…2 mk
- Q18Define the term 'amniocentesis'. Why has the government imposed a statutory ban in spite of its importance in the…2 mk
- Q19Study the figures given below and answer the questions. Cross - A Cross - B Identify in which of the crosses the…2 mk
- Q19Write the importance of following in biotechnology: Ori (Origin of Replication) Enzyme Polymerase used in Polymerase…2 mk
- Q19A laboratory assistant collected three water samples, namely river water, untreated sewage water and secondary effluent…2 mk
- Q19State any four reasons why Mendel succeeded in his genetic hybridisation experiments on garden peas.2 mk
- Q19Name the lymphoid organ that acts as a large reservoir of erythrocytes. Explain its role as a lymphoid organ.2 mk
- Q19Differentiate between opioids and cannabinoids on the basis of their Receptor site in human body. Mode of action in…2 mk
- Q19After significant reduction of BOD during secondary treatment of sewage, what further processes are carried out?…2 mk
- Q19Write any two advantages of producing plants by micro-propagation.2 mk
- Q19Study the sequence of bases in a DNA molecule that is shown below and answer the questions. What are such sequences…2 mk
- Q19Study the flow chart and answer the following questions: Identify A, B and C in the flow chart. Give one another…2 mk
- Q19Study the schematic cross between male and female honey bee given below and answer the questions that follow. Identify…2 mk
- Q19What did Henking observe in his experiments on insects that led to the discovery of sex chromosome? How did his…2 mk
- Q20(i) Given below is the schematic representation of the process of electrophoresis. Identify the alphabets representing…2 mk
- Q20Suggest how a virus-free healthy plant can be obtained from a diseased sugarcane plant. OR In order to force bacteria…2 mk
- Q20Mendel published his work on inheritance in 1865, but it remained unnoticed for over three decades. State the reasons…2 mk
- Q20Explain the type of interaction between: (i) Egret and Cattle (ii) Cuckoo and Crow OR Biodiversity exists at various…2 mk
- Q20In some cases, measuring population density by counting individuals may not be feasible. Mention two other parameters…2 mk
- Q20Analyse the following two cases of sex determination in different organisms: Case I: Males have (XO) sex chromosomes…2 mk
- Q20Why and how can bacteria be made 'competent'?2 mk
- Q20Write the role of 'ori' and 'restriction' site in a cloning vector pBR322.2 mk
- Q21Given below is a pyramid found in an ecosystem, where each bar represents the standing crop available in the trophic…2 mk
- Q21A child is born with a genetic disorder due to the deletion of a gene. Name such a gene studied by you. Explain how…2 mk
- Q21Biodiversity must be conserved as it plays an important role in many ecosystem services that nature provides. Explain…2 mk
- Q21A foreign company patented the medicinal use of turmeric already known to Indian households. Name and define this…2 mk
- Q21Differentiate between grazing food chain and detritus food chain. OR Ecological pyramids are widely accepted but they…2 mk
- Q21GEAC is a regulatory body under the Ministry of Environment, Forest and Climate Change in India. Write the full form of…2 mk
- Q21(i) What is primary productivity of an ecosystem and how is it expressed? (ii) Explain the equation given below: NPP =…2 mk
- Q21(i) Name the organ that forms a connection between foetus and the uterus of a pregnant human female. (ii) How does it…2 mk
- Q21One of the salient features of the genetic code is that it is nearly universal from bacteria to humans. Mention two…2 mk
- Q21Explain any two methods of vectorless gene transfer. OR Name the most commonly used bioreactor. List the advantages of…2 mk
- Q22There are limitations of traditional breeding techniques that led to promotion of micro-propagation? Mention two…3 mk
- Q22Draw a sectional view of seminiferous tubule of a human. Label the following cells in the seminiferous tubule: (i)…3 mk
- Q22Differentiate between wind-pollinated and insect-pollinated flowers. Give an example of each type.3 mk
- Q22Do all pollen grains remain viable for the same length of time? Support your answer with two suitable examples. How are…3 mk
- Q22List any three outbreeding devices that flowering plants have developed for cross-pollination and explain how they help…3 mk
- Q23Draw a diagram of human ovum prior to fertilization. Label any four parts. Explain how polyspermy is avoided during…3 mk
- Q23Give the scientific name of the organism used by Morgan to study sex-linked traits. Write any four reasons why this…3 mk
- Q23Study the diagram given below: Name and explain the procedure shown in the diagram. Mention one of its advantage and…3 mk
- Q23What is pedigree analysis? Mention its importance in human genetics. (2 pts.) Analyse the following pedigree and write…3 mk
- Q23What is meant by translation in protein synthesis? Explain charging of tRNA (aminoacylation of tRNA) and mention its…3 mk
- Q23Explain the polygenic inheritance pattern with the help of a suitable example.3 mk
- Q23Construct a complete transcription unit with promoter and terminator on the basis of the hypothetical coding strand…3 mk
- Q23Draw a labelled diagram of a 'replicating fork' showing the polarity. Why does DNA replication occur within such 'fork'?3 mk
- Q24Study the given chart showing evolution of plants. Answer the following questions: Identify the plant which acts as an…3 mk
- Q24What is the carrying capacity of a species in a habitat? Explain the growth curve that takes this capacity into account.3 mk
- Q24Chasmogamous flowers remain open and expose their reproductive parts. Explain how this structural feature supports…3 mk
- Q24Explain how the following microbes act as biocontrol agents: Bacillus thuringiensis Nucleopolyhedrovirus3 mk
- Q24Draw a neat diagram of enlarged view of one microsporangium of a Young anther of an angiosperm. Label the different…3 mk
- Q24Answer the following questions: Explain the different ways by which apomictic seeds can be developed. Mention one…3 mk
- Q24Mention the scientific name of the source plant and the part from which opioids are extracted. How are morphine and…3 mk
- Q24Draw a figure of E. coli vector pBR322 and label the following: (i) Origin of replication (ii) Ampicillin resistance…3 mk
- Q24How is Hardy-Weinberg expression (p^2+2 pq+q^2)=1 derived? List any two factors that disturb the genetic equilibrium.3 mk
- Q24Explain the three different ways in which natural selection operates. Explain with the help of graphs.3 mk
- Q25What is a genetic code? Why did scientists feel the need to propose a genetic code? Genetic code is said to be…3 mk
- Q25Define adaptive radiation. How did Darwin explain adaptive radiation?3 mk
- Q25How do some viruses cause cancer in humans? How do benign tumours turn malignant? How do malignant tumours harm the…3 mk
- Q25In vitro fertilization (IVF) is a popular method these days that is helping childless couples to bear a child. Write…3 mk
- Q25What is primary productivity? Why does it vary in different types of ecosystems? Why is the assimilation of energy at…3 mk
- Q25Draw a neat diagram of megasporangium of an angiosperm and label any six parts.3 mk
- Q25Mention a product of human welfare obtained with the help of each one of the following: Saccharomyces cerevisiae…3 mk
- Q25Give the schematic representation of oogenesis in human female. Indicate chromosome number also.3 mk
- Q25Draw a neat diagram of a maize grain showing the internal structure and label any five parts.3 mk
- Q26Transgenic animals are produced by man. Explain any three ways in which such animals can be beneficial to humans.3 mk
- Q26Write the scientific name of the nematode that infects tobacco plants. Also name the part of the plant that it infects.…3 mk
- Q26Compare homologous and analogous organs by giving any one point of difference. Mention the type of evolution each…3 mk
- Q26S.L. Miller conducted an experiment in 1953 to simulate the conditions of early earth in a laboratory setup. Answer the…3 mk
- Q26How is insulin different from proinsulin? Explain all the stages of how human insulin is produced through rDNA…3 mk
- Q27Study the following cases: Case I: A person bitten by a rabid dog is immediately given an injection of antitoxin for…3 mk
- Q27Suggest and describe a technique through which a healthy sugarcane plant can be obtained from virus infected sugarcane…3 mk
- Q27Explain Gause's 'Competitive Exclusion Principle' with the help of a suitable example.3 mk
- Q27A farmer grew two varieties of corn crop in field A and B. He grew normal corn crops in field A and GM corn crops in…3 mk
- Q27Study the graph given below and answer the questions that follow: (i) Write the status of food and space in the curves…3 mk
- Q27Cow dung and water are mixed and fed into a biogas plant to allow digestion of biowastes. The person performing this…3 mk
- Q27Who discovered Penicillin and how? Explain. Why is this discovery considered accidental? In what way did it prove to be…3 mk
- Q28There are many animals, which have become extinct in the wild, but continue to be maintained in zoological parks.…3 mk
- Q28A person inhales dust and pathogens but does not always fall sick. Explain how the body protects against such…3 mk
- Q28Observe the given picture carefully. A mixture of DNA with fragments ranging from 100 base pairs to 1800 base pairs…3 mk
- Q28Name the cells of the human body attacked by HIV first, when it gains entry into a human body. How does this virus…3 mk
- Q28Describe the experiment conducted by T.H. Morgan on Drosophila melanogaster involving eye colour and body colour. How…3 mk
- Q28Given below is an equation describing the growth pattern of a population: dN / dt=rN Mention the type of growth model…3 mk
- Q28Explain the level of biodiversity at genetic, species and ecological levels with the help of one example each.3 mk
- Q29Read the following passage and answer the questions that follow: Gene expresses itself in a cell system as a…4 mk
- Q29Gene manipulation is a fast emerging science. It started with the development of recombinant DNA molecules. This…4 mk
- Q29Read the following passage and answer the question that follow: The data below shows the concentration of nicotine…4 mk
- Q29Read the following passage and answer the questions that follow: The process of copying genetic information from…4 mk
- Q30Below is shown a pond that represents a self-sustaining natural ecosystem with both biotic and abiotic components…4 mk
- Q30The diagram below shows the distribution of two barnacle species, Chthamalus and Balanus on a rocky sea shore. When…4 mk
- Q30A student performed some crosses in plants and represented the result in the form of bar graphs as shown below. Each…4 mk
- Q30Read the following passage and answer the questions that follow: India is one of the megadiverse countries housing…4 mk
- Q30Read the following passage and answer the questions that follow: Immunity in our body is of two types (i) Innate…4 mk
- Q30Read the following passage and answer the questions that follow: We know that plasmids and bacteriophages are the most…4 mk
- Q31In angiosperms, the female gametophyte develops from a single cell of megasporangium. (i) Name that cell of…5 mk
- Q31In the given diagram - 'A' is an embryonic stage that gets transformed into 'B', which in turn gets implanted in the…5 mk
- Q31(i) Describe the series of experiments conducted by Frederick Griffith. Comment on the significance of the result…5 mk
- Q31Briefly explain the events of fertilisation and implantation in an adult human female. OR (i) Arrange the following…5 mk
- Q31The following questions are based on the classic experiment conducted by Hershey and Chase. (i) Why were bacteriophages…5 mk
- Q31(i) Explain the role of stigma in pollen pistil interaction. (ii) Describe the post pollination events leading to…5 mk
- Q31Trace the events from fertilization till implantation of blastocyst in human female. Also mention the site where…5 mk
- Q32(i) Explain any two basic principles/core techniques on which biotechnology is based. (ii) Describe any three key tools…5 mk
- Q32(i) Draw the structure of an antibody molecule and label any four of its parts. (ii) Differentiate between active and…5 mk
- Q32Write the types and locations of the genes causing thalassemia in humans. State the cause and symptoms of the disease.…5 mk
- Q32(i) Watson and Crick's discovery of double helical structure was based on which two findings. Also mention the name of…5 mk
- Q32Observe the segment of mRNA given below and answers the questions given below: (i) Explain and illustrate the steps…5 mk
- Q32(i) Identify the structure shown above and name the process taking place. (ii) Write the source of energy for the…5 mk
- Q32Work out separate monohybrid crosses up to F_2 generation between two pea plants and two Antirrhinum plants, both…5 mk
- Q32Study the flow chart given below. Name the hormones involved at each stage and explain their functions. OR (i) Draw a…5 mk
- Q32Describe how the lac operon operates both in the presence and absence of an inducer in E. coli. OR (i) Differentiate…5 mk
- Q33(i) Name the protozoan species that is responsible for causing the most serious and even fatal malarial disease. (ii)…5 mk
- Q33A 30 year old man was admitted to a hospital with recurrent infections, weight loss, prolonged fever. His blood report…5 mk
- Q33(i) Draw a neat sectional view of seminiferous tubule of a human testes showing spermatogenesis. Label any five stages.…5 mk
- Q33(i) EcoR I has played a very important role in rDNA technology. (I) Explain the convention for naming EcoR I. (II)…5 mk
- Q33Oogenesis is a discontinuous process that begins before birth and is completed after puberty. (i) Trace the development…5 mk
Other Biology years
Answers come from CBSE’s own marking schemes. How we source them.