CQ1. A lab culture has cells with no nuclear membrane but green pigments that release O₂ in light. In Whittaker’s system this organism is best placed in:
CQ2. A soil microbe oxidises NH₃ to get energy and uses CO₂ as carbon source. Its nutrition type is:
CQ3. A museum specimen shows head fused with thorax under one carapace. This cephalothorax points to phylum:
CQ4. A crop has parallel leaf venation, fibrous roots and one cotyledon. It is best classified as:
CQ5. In mature xylem of a stem slide, which component is still living?
CQ6. Mangrove plants send vertical roots above waterlogged mud for gas exchange. These are:
CQ7. Potato stores food in a swollen underground tip with ‘eyes’ (buds). This is a:
CQ8. Pink legume nodules fix N₂ because nitrogenase is protected by low free O₂. The pink O₂-buffer protein is:
CQ9. Which bacterium typically forms nodules with legumes and fixes atmospheric nitrogen?
CQ10. In C4 plants, the first CO₂ acceptor in mesophyll is:
CQ11. During non-cyclic photophosphorylation, which set is produced?
CQ12. Net gain from complete glycolysis of one glucose to two pyruvate in cytosol is typically:
CQ13. The plasma protein converted to fibrin threads during clotting is:
CQ14. Among reptiles, a four-chambered heart (complete ventricular separation) is found in:
CQ15. Oversecretion of thyroxine typically causes:
CQ16. In angiosperms, fusion of one male gamete with two polar nuclei forms:
CQ17. F1 tall plant crossed with homozygous dwarf (tt) is a:
CQ18. Formation of mRNA from DNA is called:
CQ19. In grass → insect → frog → snake, the frog occupies the:
CQ20. The largest lymphoid organ in the human body is the:
3 marks · Apply processes to new situations · Try first, then show model answer.
AQ1. A farmer sees pink root nodules on pea. Explain (a) which microbe is likely present, (b) why the nodule looks pink, (c) how this helps plant protein synthesis.
Model Answer
(a) Rhizobium (symbiotic fixer). (b) Leghaemoglobin buffers O₂, giving pink colour. (c) Fixed NH₃ is used to make amino acids/proteins; plant gets usable N without buying nitrate fertiliser alone.
AQ2. At noon a green leaf releases O₂; at night the same cells take up O₂. Explain using light reaction and cellular respiration (sites and products).
Model Answer
Day: photolysis of H₂O in thylakoids → O₂ + ATP/NADPH; Calvin in stroma makes sugar. Night: no light reaction; mitochondria oxidise sugar (glycolysis cytosol → Krebs/ETC) and consume O₂ to make ATP. Both can occur in living cells; net O₂ exchange flips with light.
AQ3. Maize thrives in hot bright fields better than wheat for photorespiration risk. Using CO₂ acceptors and first products, explain C4 advantage.
Model Answer
C4: PEP accepts CO₂ in mesophyll → OAA (4C); CO₂ concentrated to bundle sheath for Rubisco/Calvin. C3: RuBP → PGA; more photorespiration in heat. C4 pump reduces O₂ competition at Rubisco.
AQ4. A student says glycolysis ‘gives 4 ATP net’. Correct the claim by naming the three phases and the true net yield.
Model Answer
Investment uses 2 ATP; cleavage splits hexose; payoff makes 4 ATP + 2 NADH → net 2 ATP + 2 NADH + 2 pyruvate per glucose in cytosol. ‘4 ATP’ ignores the 2 ATP spent early.
AQ5. After a high-fat meal, milky fluid appears in intestinal lymphatics. Contrast blood and lymph routes and why fats use lymph.
Model Answer
Blood: heart → arteries → capillaries → veins → heart (closed). Lymph: tissue fluid → vessels → nodes → ducts → veins (one-way). Long-chain fats as chylomicrons enter lacteals (lymph) then blood, avoiding direct portal flooding.
AQ6. A person with low fibrinogen and a damaged spleen faces two risks. Link each molecule/organ to function.
Model Answer
Fibrinogen → fibrin clot mesh; low level → bleeding risk. Spleen filters blood and houses lymphocytes; damage impairs blood filtration/immune surveillance.
AQ7. Child A has excess GH; adult B has excess thyroxine. Name likely gland issues and one contrasting symptom pair.
Model Answer
A: anterior pituitary GH excess → gigantism (height). B: hyperthyroidism → high BMR, weight loss, heat intolerance (not height growth like child GH). Different axes: somatotrophs vs thyroid hormone.
AQ8. A toxin blocks Na⁺ channels only on the axon. Which labelled parts still receive signal, and what fails?
Model Answer
Dendrites/cell body may still receive synaptic input; axon cannot propagate action potential to terminals → no neurotransmitter release to next cell. Axon = output cable.
AQ9. Coconut water is liquid endosperm. Explain its origin using double fertilisation products.
Model Answer
One male gamete + egg → zygote (2n embryo). Other + polar nuclei → PEN (3n) → endosperm. Coconut water/kernel = endosperm nourishing embryo.
AQ10. Peepal syconium is a closed receptacle with a pore. Name the inflorescence type and one label you must draw.
Model Answer
Hypanthodium (Ficus). Labels: fleshy receptacle, ostiole, male/female flowers inside. Not a simple raceme.
AQ11. Couple wants reversible barrier method vs permanent female surgical method. Name one each and mode of action.
Model Answer
Barrier: condom — blocks sperm meeting ovum. Surgical: tubectomy — cut/tie oviducts so ovum never meets sperm. Barrier reversible; tubectomy permanent sterilisation.
AQ12. Fill the pathway: ovary releases egg → meets sperm in ___ → zygote → cleavage → ___ → implants in ___.
Model Answer
Fallopian tube/oviduct; morula (then blastocyst); uterus/endometrium. Order: ovary → tube fertilisation → morula → uterine implantation.
AQ13. TTRR (tall red) × ttrr (dwarf white). State F1 phenotype and F2 phenotypic ratio if independent assortment.
Model Answer
F1 all TtRr tall red. F2 9 tall red : 3 tall white : 3 dwarf red : 1 dwarf white (9:3:3:1).
AQ14. Mirabilis red × white gives all pink F1. What is F2 phenotypic ratio and why not 3:1?
Model Answer
1 red : 2 pink : 1 white. Heterozygote intermediate (incomplete dominance) so phenotype tracks genotype 1:2:1, not 3:1 complete dominance.
AQ15. Why does lagging strand need Okazaki fragments and DNA ligase while leading strand does not?
Model Answer
DNA pol only builds 5′→3′. At fork, one template allows continuous leading synthesis; the other needs short fragments (Okazaki) later joined by ligase.
AQ16. In E. coli, lactose appears in medium. Name inducer effect and where RNA polymerase binds.
Model Answer
Lactose/allolactose acts as inducer (inactivates repressor). RNA polymerase binds promoter; structural genes z,y,a transcribed for lactose enzymes.
AQ17. Build one producer + three consumers chain and state trophic level of the top carnivore.
Model Answer
e.g. grass → grasshopper → frog → snake. Snake = 4th trophic level (tertiary consumer). Producers always level 1.
AQ18. Which floral adaptation forces self-pollination, and name one that promotes cross-pollination instead.
Model Answer
Cleistogamy (closed flowers) forces selfing. Cross promoted by dichogamy, self-incompatibility, unisexual flowers, etc.
AQ19. Weaned child on starchy gruel develops oedema and moon face; another is severely wasted without oedema. Name both PEM types.
Model Answer
Oedema/moon face → kwashiorkor (protein lack). Severe wasting no oedema → marasmus (energy + protein starvation). Both undernutrition/PEM.
AQ20. Hepatitis B vaccine is recombinant; vaccination trains memory cells. Link production (L30) to immune memory (L31).
Model Answer
L30: antigen gene expressed in microbes → purified protein vaccine. L31: antigen triggers adaptive immunity → antibodies + memory B/T cells so later infection is faster-controlled.
5 marks · Integrate concepts across chapters · Deep understanding.
ZQ1. Trace how a legume plant builds protein: atmospheric N₂ → amino acid, and carbon skeletons from photosynthesis → respiration ATP. Name key enzymes/sites.
Model Answer
N₂ fixed by Rhizobium nitrogenase (nodules; O₂ buffered by leghaemoglobin) → NH₃ → amino acids (amination/transamination). Carbon: CO₂ fixed Calvin/C4 → sugars; respiration (glycolysis cytosol, Krebs/ETC mitochondria) yields ATP/NADH for biosynthesis. Integration: N supply + C skeletons + energy.
ZQ2. Why are food chains short? Use photosynthetic capture, ~10% transfer, and cellular respiration energy loss.
Model Answer
Producers capture little of sunlight into biomass. Each trophic step transfers roughly ~10%; rest lost as heat via metabolism/respiration. Insufficient energy remains for many levels → short chains (L25) rooted in photosynthesis input and respiration loss (L11–L12).
ZQ3. Compare living cells specialised for: (i) storage in stem tuber, (ii) gas exchange root in swamp, (iii) conduction of water. Name tissue/modification.
Model Answer
(i) Parenchyma in stem tuber (potato). (ii) Pneumatophores. (iii) Xylem vessels/tracheids (dead conduits) with living xylem parenchyma assisting. Structure matches storage vs aeration vs bulk flow.
ZQ4. A runner’s heart rate rises, adrenaline surges, and later antibodies form after a vaccine. Assign systems and time scales.
Model Answer
Heart rate: neural + endocrine (ANS, adrenaline) seconds–minutes (L15/L17). Vaccine: adaptive immunity days–weeks — B/T lymphocytes, memory (L31). Fast electrical/chemical vs slower clonal immune response.
ZQ5. Seed forms after double fertilisation; a monohybrid test cross checks a tall plant’s genotype. Connect sporophyte seed to Mendelian test.
Model Answer
Double fertilisation → embryo + endosperm in seed (next sporophyte generation). Phenotype tall may be TT or Tt; test cross with tt distinguishes: all tall → TT; 1:1 tall:dwarf → Tt. Life cycle meets genetics.
ZQ6. Incomplete dominance gives pink flowers; transcription makes mRNA for pigment enzyme. Outline DNA → trait path and why heterozygote is pink.
Model Answer
Gene (DNA) transcribed → mRNA translated → enzyme/protein → pigment. Heterozygote has one functional allele → intermediate enzyme/pigment → pink (incomplete dominance), not full red.
ZQ7. To mass-produce human insulin, which central-dogma step is engineered in bacteria, and which rDNA tools cut/join DNA?
Model Answer
Insert human insulin gene into plasmid; bacteria transcribe/translate it (hijack dogma). Restriction enzymes cut; ligase joins; host amplifies recombinant plasmid (L30 tools + L23 expression).
ZQ8. Uncontrolled population growth strains food supply. Link J/S curves to PEM risk in children 1–5 years.
Model Answer
J-curve: resources abundant, exponential rise. S-curve: limited food, approaches carrying capacity. Crowding + poor weaning diets → marasmus/kwashiorkor PEM in young children (L28) when protein-energy intake fails (L21/L25 pressures).
ZQ9. Compare first-generation attenuated vaccine idea (Jenner/cowpox logic) with recombinant hepatitis B vaccine production.
Model Answer
First-gen: weakened/related live organism trains immunity (historical cowpox→smallpox protection). Recombinant: antigen gene cloned, protein harvested — no whole pathogen; safer defined antigen, still induces antibodies/memory (L30 production + L31 adaptive response).
ZQ10. Blue-green algae colonise bare rock, then lichens, mosses, shrubs, trees. Name the ecological process and the kingdom of the pioneer prokaryote.
Model Answer
Primary ecological succession (seral stages to climax). Pioneer blue-green algae = cyanobacteria → Monera (prokaryotes). Succession rebuilds community structure over time (L25) starting from L2 microbes.