Previous Year Questions/ISC/Specimen papers
Created by Titas Mallick
Biology Teacher • M.Sc. Botany • B.Ed. • CTET (CBSE) • CISCE Examiner
BioNotesBioNotesCreated by Titas Mallick
Biology Teacher • M.Sc. Botany • B.Ed. • CTET (CBSE) • CISCE Examiner
Online
Complete specimen question paper and answer key for ISC Class XII Biology Paper 1 (Theory) 2027 examination with 18 questions across 4 sections covering all major biology topics.
Maximum Marks: 70
Time Allotted: Three Hours
Reading Time: Additional Fifteen Minutes
Note: The Specimen Question Paper in the subject provides a realistic format of the Board Examination Question Paper and should be used as a practice tool.
(Question 1, eighteen subparts, 1 mark each)
Answer the following questions briefly.
(i) Stuti ate a cake containing nuts and immediately developed swelling of the lips and difficulty in breathing. Identify the chemical responsible for Stuti's condition. (Recall) [1] (a) Insulin (b) Histamine (c) Interferon (d) Adrenaline
(ii) A survey was conducted to study the age structure of a human population — Adults: 60,000; Children: 35,000; Old: 50,000. Identify the MOST appropriate shape of the age pyramid. (Evaluate) [1] (a) Pyramidal (b) Triangular (c) Urn-shaped (d) Bell-shaped
(iii) In a single-stranded segment of a DNA molecule, the base ratio (A+T):(G+C) is found to be 0.3:1. What will be the ratio (A + G):(T + C) for the entire double-stranded DNA molecule? (Apply) [1] (a) 1:1 (b) 3:10 (c) 10:3 (d) 13:3
(iv) Identify the vectors used for cloning genes into eukaryotic organisms. (Recall) [1] (P) BAC (Q) Bacteriophages (R) Ti plasmid (S) Disarmed retroviruses (a) Only (P) and (Q) (b) Only (P) and (R) (c) Only (Q) and (S) (d) Only (R) and (S)
(v) In an ecosystem, interspecific interactions are marked (+) beneficial, (-) harmful, (0) neutral. Which represents amensalism? (Understand) [1] (a) Species A (-), Species B (0) (b) Species A (+), Species B (+) (c) Species A (-), Species B (-) (d) Species A (+), Species B (0)
(vi) Assertion: Excess dose of cocaine produces a sense of euphoria, increased energy and hallucinations. Reason: Cocaine interferes with the transport of dopamine leading to abnormalities in the brain. (Analyse) [1] (a) Both A and R true, R correct explanation of A (b) Both A and R true, R not correct explanation of A (c) A true, R false (d) Both A and R false
(vii) Assertion: In a majority of flowering plants, embryo sac development is called monosporic. Reason: Embryo sac develops from one of the two megaspores formed by meiosis of megaspore mother cell. (Analyse) [1]
(viii) A patient was found to have a mass of pancreatic cells in the liver producing large amounts of amylase; a tumor was found in the pancreas. What type of tumour had developed? (Understand) [1]
(ix) A research scholar isolated a novel restriction enzyme from Bacillus anthracis strain ZT4 — the third restriction enzyme extracted from this strain. Derive the scientific name using standard nomenclature rules. (Understand) [1]
(x) Why do leguminous crops fertilise the soil but cereals do not? (Understand) [1]
(xi) The pie chart represents global biodiversity of invertebrates. Which phylum does 'B' represent? (Recall) [1]
(xii) Construct an ecological pyramid of biomass for: Grass → Deer → Fleas. (Understand) [1]
(xiii) Sigma factor : Initiation :: __________ : Termination. (Understand) [1]
(xiv) A retroviral RNA undergoes reverse transcription producing a double-stranded DNA with a six-nucleotide palindromic sequence: 5′– GGA — – 3′ 3′– — — — – 5′ Obtain the six-nucleotide palindromic sequence on the 3′–5′ strand. (Create) [1]
(xv) A rural area has population density 150/sq. km over 250 sq. km. Total population? (Apply) [1]
(xvi)(a) Expand the abbreviation KVIC. (Recall) [1]
(xvi)(b) Alexander Fleming discovered an antibiotic later purified by a team of scientists. Name them. (Recall) [1]
(xvii) State the underlying principle of the ELISA test. (Recall) [1]
(xviii)(a) Give a reason: Our government has imposed strict conditions/regulations on Medical Termination of Pregnancy. (Recall) [1]
(xviii)(b) Give a reason: In the biolistic method of gene transfer, microparticles are preferred to be made of gold rather than copper. (Analyse) [1]
(Seven questions × 2 marks each)
An image represents an ecological hypothesis proposed by Paul Ehrlich (airplane with rivets popping out). Identify and explain this hypothesis. (Understand)
An alien gene was ligated at the Sal I site of pBR322 plasmid, affecting a selectable marker. (i) Name the selectable marker affected. (Recall)
(ii) State the underlying principle. (Recall)
A scientist retrieved an embryo just after implantation, for cloning. (i) Identify the specific stage retrieved. (Recall)
(ii) Which part is most suitable for cloning? (Understand)
Venn diagram of contraceptive methods (Lippe's loop, Multiload-375, LNG-20). (i) Which method occupies the shaded (common) region? (Analyse)
(ii) How does Multiload–375 function as a contraceptive agent?
(i) Pie chart: 9000 pea plants, Hardy-Weinberg equilibrium, 360 plants are tt (homozygous recessive). (a) Frequency of dominant allele (T)? (Apply)
(b) Number of heterozygous pea plants? (Apply)
OR
(ii) A gene transcribes an mRNA of 603 nucleotides (incl. stop codon); the 150th nucleotide was deleted during replication. (a) How many amino acids remain unchanged before the mutation site? (Apply)
(b) Explain how the mutation affects the protein. (Analyse)
A couple unable to conceive for five years; wife has normal ovulatory cycles and healthy Fallopian tubes; husband has low sperm count. (i) Suggest an assisted reproductive technique. (Understand)
(ii) State one specific sperm abnormality (other than low count) that would necessitate this technique over standard IVF. (Understand)
(i) Cattle excreta is used to produce domestic fuel. (a) Name the largest component of this fuel. (Recall)
(b) Biological name of the microbe responsible. (Recall)
OR
(ii) Flowchart of Plasmodium life cycle (Mosquito bite → Liver stage → Stage X → Blood meal → Fertilisation → Sporogony → back to Mosquito bite). (a) Identify Stage 'X'. (Recall)
(b) Name the toxin responsible for recurring chills and fever in malaria. (Recall)
(Seven questions × 3 marks each)
(i) Draw a neat, labelled diagram of the Graafian follicle. (Recall)
OR
(ii) Draw a neat, labelled diagram of the L.S. of an anatropous ovule. (Recall)
(i) A biotechnologist inserts a drought-tolerance gene into isolated wheat somatic cells and needs to regenerate thousands of genetically identical, pathogen-free plants. (a) Which technique should be used? (Understand)
(b) Explain two major steps. (Understand)
OR
(ii) Bar graph: β-galactosidase activity — Medium A: 2, Medium B: 95 — with lac operon states. (a) Why is the operon switched OFF in one medium? (Understand)
(b) Explain the lac operon as negative regulation, with reference to the operator site. (Understand)
(i) pBR322 was used in making genetically engineered insulin. What was its possible role? (Analyse)
(ii) Can this plasmid be used for gene transfer in plants? Substantiate. (Evaluate)
Graph: seasonal variation in Net Primary Productivity (surface vs. 1m depth) in a marshy area of India. (i) Account for the difference in primary productivity at points 'X' and 'Y'. (Analyse)
(ii) GPP of a terrestrial ecosystem is 2700 kg/m²/yr; 3/10th of energy is used for respiration. Calculate NPP. (Apply)
Describe three types of natural selection, illustrating each with a suitable graph. (Recall)
mRNA of E. coli: 5′ GUG GCU CAA 3′ → derived as valine, alanine, glycine. Then asked to derive mRNA from arginine, serine, proline (unsuccessful). (i) Why could Sneha not derive the mRNA sequence? (Understand)
(ii) GCU codon changed to GCA and the amino acid remained alanine in a fungal cell. Which feature of the genetic code enabled this? (Recall)
(iii) Deduce the anticodon sequence of the tRNA (5′→3′). (Apply)
Patients A (Typhoid) and B (Chikungunya) — lymphocytes produced immunological proteins 'X' and 'Y' respectively. Protein X: slow but long-lasting, not effective against cancer cells. Protein Y: rapid but temporary, effective against cancer cells. (i) Identify proteins 'X' and 'Y'. (Understand)
(ii) How does protein 'Y' develop an immunological response in Chikungunya? (Analyse)
(Three questions × 5 marks each)
(i) Marfan Syndrome (FBN1 gene mutation) — pedigree chart given (three generations, affected individuals in each generation, both sexes affected, appears in every generation). (a) Identify the type of inheritance. (Understand)
(b) If parents are heterozygous, calculate probability of an unaffected child using a Punnett square. (Apply)
OR
(ii) Prisha has two nucleotides — (1) with a reactive 2′–OH group on the sugar, (2) without it. Which should she choose as ideal genetic material? (Analyse)
(i)(a) Differentiate: (1) Leydig cells vs Sertoli cells — based on location in testis. (Analyse)
(2) Corpus luteum vs Placenta — based on endocrine function. (Analyse)
(b) What would happen if the zona pellucida disappears prematurely at the morula stage? (Evaluate)
(c) Name and state the function of the middle wall of the human uterus. (Recall)
OR
(ii)(a) Why are fresh pollens used for pea hybridisation but preserved pollens mandatory for wheat? (Analyse)
(b) Table: Fruit X — integument cells develop into embryo; Fruit Y — ovary develops into seedless fruit via phytohormones; Fruit Z — peduncle contributes to fruit formation. (1) Which exhibits polyembryony? Will embryos show genetic variation? Justify. (Evaluate)
(2) Identify the fruit type of 'Y'. (Recall)
(i) Predator-prey graph (prey peaks lead, predator peaks lag) over 12 years. (a) Assume 80% of the predator population is wiped out by a viral disease at Year 6. Construct the graph from Year 6 onward. (Create)
(b) Interpret the population dynamics responsible for the changes. (Analyse)
OR
(ii) A population of 100 beetles introduced into an environment with carrying capacity 500; intrinsic rate of increase r = 0.2/year. (a) Calculate the change in population size after the first year. (Apply)
(b) Draw the population growth curve (logistic/S-shaped) labelling: Initial population, Carrying capacity, Phase of maximum growth rate, Stationary phase. (Create)
Compiled as a solved question–answer reference from the ISC Specimen Question Paper 2027 (Biology Paper 1, Theory) and its official Answer Key, CISCE.
(i) Answer: (b) Histamine**
(ii) Answer: (c) Urn-shaped**
(iii) Answer: (a) 1:1**
(iv) Answer: (d) Only (R) and (S)**
(v) Answer: (a) Species A (-), Species B (0)**
(vi) Answer: (a) Both Assertion and Reason are true, and Reason is the correct explanation for Assertion.**
(vii) Answer: (c) Assertion is true and Reason is false.** (Note: Embryo sac develops from one of the FOUR megaspores, not two — hence Reason is false.)
(viii) Answer: Metastatic tumour**
(ix) Answer: Ban Z III** (Genus initial + species initial + strain + Roman numeral for order of isolation)
(x) Answer:** Legumes have a symbiotic association with Rhizobium bacteria which fixes atmospheric nitrogen, while cereals do not have this association.
(xi) Answer: Phylum Mollusca**
(xii) Answer:** An inverted-then-upright (spindle-shaped) pyramid — broad base (Grass), narrower middle (Deer), with a small bulge/wider top (Fleas), since parasite biomass at the top can exceed that of the host level immediately below it while still being far less than producer biomass.
(xiii) Answer: Rho factor**
(xiv) Answer: 3′ – CCTAGG – 5′**
(xv) Answer:** Total population = 150 × 250 = 37,500
Answer: Khadi and Village Industries Commission**
Answer: Ernest Chain and Howard Florey**
(xvii) Answer: Antigen–antibody reaction**
Answer:** It prevents illegal misuse for sex-selective abortions (female foeticide).
Answer:** Gold is inert and non-toxic, whereas copper is reactive and toxic.
Answer: Rivet Popper Hypothesis**
(i) Answer: Tetracycline resistance (Tet^R) gene**
(ii) Answer: Insertional inactivation**
(i) Answer: Blastocyst**
(ii) Answer: Inner cell mass**
(i) Answer: Intrauterine device (IUD)**
(ii) Answer:** Multiload-375 is a copper-releasing IUD; copper reduces sperm motility and increases phagocytosis of sperm.
(i) (a) Answer: p = 0.8** (q² = 360/9000 = 0.04, q = 0.2, so p = 1 – 0.2 = 0.8)
(b) Answer:** 2pq = 2 × 0.8 × 0.2 = 0.32 of 9000 = 2880 plants
(ii) (a) Answer: First 49 amino acids remain unchanged** (150th nucleotide falls within the 50th codon (nucleotides 148–150), so the first 49 codons/amino acids are unaffected)
(b) Answer:** The 50th amino acid and all subsequent amino acids are likely to be altered due to a frameshift mutation.
(i) Answer: Intracytoplasmic Sperm Injection (ICSI)**
(ii) Answer:** Poor sperm motility / abnormal shape of sperm
(i) (a) Answer: Methane**
(b) Answer: Methanococcus**
(ii) (a) Answer: Merozoite**
(b) Answer: Haemozoin**
(i) (ii)
(i) (a) Answer: Micropropagation / Plant tissue culture**
(b) Answer:**
(ii) (a) Answer:** In Medium A, only glucose is present and the inducer (lactose) is absent, so the repressor protein remains bound to the operator site, blocking RNA polymerase. Thus the operon is switched OFF.
(b) Answer:** In Medium B, only lactose is present. It stops the repressor protein from binding to the operator site, allowing RNA polymerase to transcribe the structural genes — the operon gets switched ON.
(i) Answer:** The plasmid acted as a suitable vector.
(ii) Answer: No.** It lacks the T-DNA / vir gene system necessary for transferring DNA into plant cells.
(i) Answer:** Primary productivity decreases with a decrease in temperature.
(ii) Answer:** R = 3/10 × 2700 = 810 kg/m²/yr NPP = GPP − R = 2700 − 810 = 1890 kg/m²/yr
Answer:**
(i) Answer:** Due to degeneracy of the genetic code — because one amino acid can be coded by more than one codon, the exact mRNA sequence cannot be uniquely determined from the amino acid sequence.
(ii) Answer:** Genetic code is universal. (Note: This reflects degeneracy of the code enabling synonymous codon substitution without changing the amino acid — the answer key states "Genetic code is universal.")
(iii) Answer: 5′ UUG AGC CAC 3′**
(i) Answer: X — Antibodies; Y — Interferons**
(ii) Answer:** Interferons stimulate the cellular DNA to produce a series of antiviral proteins/enzymes. These enzymes bind to viral mRNA and block viral protein synthesis.
(i) (a) Answer: Autosomal dominant**
(b) Answer:**
| A | a | |
|---|---|---|
| A | AA | Aa |
| a | Aa | aa |
Probability of unaffected child (aa) = 25%
(ii) Answer: Nucleotide (2).**
Answer:**
| Leydig cells | Sertoli cells |
|---|---|
| Located in the interstitial spaces (connective tissue) surrounding the seminiferous tubules | Located in the seminiferous epithelium within the seminiferous tubules |
Answer:**
| Corpus luteum | Placenta |
|---|---|
| Secretes progesterone | Secretes chorionic gonadotropin, estrogen, progesterone, relaxin, hPL |
(b) Answer:** Without the zona pellucida (which prevents adhesion), the morula may prematurely attach to the wall of the Fallopian tube, potentially leading to an ectopic pregnancy.
(c) Answer: Myometrium** — brings about powerful contractions of the uterus during parturition.
Answer:** Pea belongs to family Leguminosae, whose pollen remains viable for several months to years. Wheat pollen, however, remains viable for only about 30 minutes, so preserved (stored) pollen must be used to allow controlled hybridisation.
(b) Answer: Fruit X.** It will not exhibit genetic variation, because the embryo develops from the cells of the integument by mitosis, not by fertilisation (apomictic/adventive embryony).
Answer: Parthenocarpic fruit**
(i) (a) Answer:** From Year 6, plot the predator curve starting at ~20% of its Year-6 value (a sharp drop), then rising gradually over subsequent years as prey become abundant; plot the prey curve dipping initially (predation still occurring) before rising sharply due to reduced predation pressure, then gradually declining again as predators recover — approaching a new cyclical balance.
(b) Answer:**
(ii) (a) Answer:** dN/dt = rN(K−N)/K dN/dt = 0.2 × 100 × (500−100)/500 dN/dt = 20 × 0.8 = 16
(b) Answer:** An S-shaped (sigmoid) logistic growth curve: