Class 12/Question Bank/Competency Based
Created by Titas Mallick
Biology Teacher • M.Sc. Botany • B.Ed. • CTET (CBSE) • CISCE Examiner
Created by Titas Mallick
Biology Teacher • M.Sc. Botany • B.Ed. • CTET (CBSE) • CISCE Examiner
Competency Based Questions on Sexual Reproduction in Flowering Plants
1. Analyze the Scenario: A botanist observes that a particular plant species produces two types of flowers: one type that never opens (Cleistogamous) and another type that opens normally (Chasmogamous). Which of the following is most likely true? a) The plant relies solely on xenogamy. b) The closed flowers ensure heterozygosity. c) The plant produces pure lines for traits in the closed flowers. d) The open flowers are incapable of setting seeds. Answer: c) The plant produces pure lines for traits in the closed flowers. Explanation: Cleistogamous flowers never open, ensuring 100% self-pollination (Autogamy). Constant self-pollination leads to homozygosity and the development of pure lines for those traits.
2. Assertion (A): Apomictic seeds are highly advantageous for the hybrid seed industry. Reason (R): Apomixis prevents the segregation of characters in the hybrid progeny. a) Both A and R are true and R is the correct explanation of A. b) Both A and R are true but R is not the correct explanation of A. c) A is true but R is false. d) A is false but R is true. Answer: a) Both A and R are true and R is the correct explanation of A. Explanation: Hybrid seeds are expensive because farmers must buy them every year (traits segregate in F2). Apomixis produces seeds without fertilization (clones), so the desirable hybrid traits are fixed and do not segregate.
3. Evaluate the Impact: A farmer plants only female papaya plants to maximize yield but observes zero fruit set. What is the fundamental biological error? a) Papaya is monoecious. b) Papaya is dioecious; he ignored the need for male plants for pollination. c) Papaya is parthenocarpic. d) Papaya flowers are cleistogamous. Answer: b) Papaya is dioecious; he ignored the need for male plants... Explanation: Papaya is a dioecious species (male and female flowers on different plants). Without male plants nearby, there is no source of pollen for the female flowers to set seeds and fruit.
4. Assertion (A): Continued self-pollination often leads to inbreeding depression. Reason (R): Self-pollination introduces new genetic variations. a) Both A and R are true and R is the correct explanation of A. b) Both A and R are true but R is not the correct explanation of A. c) A is true but R is false. d) A is false but R is true. Answer: c) A is true but R is false. Explanation: Self-pollination reduces variation and increases homozygosity, which often exposes harmful recessive alleles (Inbreeding Depression). It does not introduce new variations.
5. Predict the Outcome: If a scientist removes the filiform apparatus from the synergids before pollination, what will happen? a) The egg cell will die. b) The pollen tube will fail to enter the synergid. c) The antipodal cells will proliferate. d) Double fertilization will occur twice. Answer: b) The pollen tube will fail to enter the synergid. Explanation: The filiform apparatus guides the pollen tube towards the egg apparatus by releasing chemical attractants and providing a physical entry point.
6. Analyze the Adaptation: A plant has flowers that are dull-colored, produce a strong fruity/fermenting odor, and bloom only at night. Which pollinator is it adapted for? a) Bees b) Wind c) Bats d) Birds Answer: c) Bats (Chiropterophily) Explanation: Bats are nocturnal and attracted to strong, musky or fermenting odors. They do not rely on bright colors (which are invisible in the dark).
7. Calculation: If a fruit contains 60 seeds, what is the minimum number of meiotic divisions required to produce them? a) 60 b) 75 c) 120 d) 90 Answer: b) 75 Explanation:
8. Assertion (A): The endosperm in angiosperms is typically triploid (3n). Reason (R): It is formed by the fusion of one male gamete with two polar nuclei. a) Both A and R are true and R is the correct explanation of A. b) Both A and R are true but R is not the correct explanation of A. c) A is true but R is false. d) A is false but R is true. Answer: a) Both A and R are true and R is the correct explanation of A. Explanation: This is the process of Triple Fusion (), a unique event in double fertilization.
9. Identify the mismatch: Which pair is correct? a) Light, non-sticky pollen - Entomophily b) Long, ribbon-like pollen with mucilage - Hydrophily c) Bright red flowers, no scent - Chiropterophily d) Feathery stigma - Zoophily Answer: b) Long, ribbon-like pollen with mucilage - Hydrophily. Explanation: These are adaptations for water-pollinated plants (like Zostera) to prevent the pollen from getting wet and to aid in floating.
10. Critical Thinking: Evolutionary advantage of coleoptile and coleorhiza in monocots? a) Nutrition. b) Photosynthesis. c) Physical protection to the delicate plumule and radicle during soil penetration. d) Nitrogen fixation. Answer: c) Physical protection... Explanation: These sheaths protect the growing tips of the embryonic shoot and root as they push through abrasive soil particles during germination.
11. Assertion (A): Emasculation is necessary in artificial hybridization of papaya. Reason (R): Papaya plants produce unisexual flowers. a) Both A and R are true. b) Both A and R are true but R is not explanation. c) A is true but R is false. d) A is false but R is true. Answer: d) A is false but R is true. Explanation: Emasculation is the removal of anthers from a bisexual flower. Since papaya is unisexual (dioecious), the female flower has no anthers to remove.
12. Analyze the structure: Premature degeneration of the Tapetum in an anther leads to: a) Delayed dehiscence. b) Sterile pollen grains due to lack of nutrition. c) Thickened epidermis. d) Fast cell division. Answer: b) Sterile pollen grains due to lack of nutrition. Explanation: The tapetum is the innermost nutritive layer. If it fails, the developing microspores don't get the nourishment (and sporopollenin) needed to mature.
13. Application: Sequence for hybridizing a self-pollinating crop? a) Emasculation -> Bagging -> Pollination -> Rebagging b) Bagging -> Emasculation -> Pollination -> Rebagging Answer: a) Emasculation -> Bagging -> Pollination -> Rebagging. Explanation: First remove anthers (Emasculation) to prevent selfing, then cover (Bagging) to prevent stray pollen, then add desired pollen, then cover again (Rebagging).
Vanilla is an orchid native to Mexico, pollinated by Melipona bees. In Madagascar, it grows but sets no fruit naturally.
14. Analyze: Why failure in Madagascar? Answer: The specific co-evolved pollinator (Melipona bee) was absent in the new habitat.
15. Evaluate: Hand-pollination involves lifting a flap (rostellum) to touch anther to stigma. What barrier is this? Answer: (b) Herkogamy. This is a physical or spatial barrier that prevents the plant from self-pollinating naturally.
In Wheat, temperatures >35°C lead to shriveled, non-viable pollen.
16. Diagnose: Failure point? Answer: (c) Microsporogenesis or Pollen Viability. The male gametophyte is failing due to heat.
17. Hypothesize: Which anther layer is damaged? Answer: (c) Tapetum. It is the most metabolically active and sensitive layer; its failure starves the pollen.
Farmers save seeds from hybrid tomatoes, but the F2 plants show loss of yield and variation.
18. Explain: Why loss of hybrid vigor? Answer: Because during meiosis in the hybrid (F1) plant, the alleles Segregate and Assort Independently, breaking up the specific "winning" combination of genes that gave the hybrid its superior traits.
19. Propose: Biological solution to "fix" the vigor? Answer: (c) Apomixis. If the hybrid can produce seeds asexually (clones), the vigor will be maintained forever.
20. Designing an Experiment: Pollinator identification. Answer:
21. Journey of the Male Gamete (Concept Map): Answer: Microspore Mother Cell (2n) --(Meiosis)--> Microspore (n) --(Mitosis)--> Pollen Grain (Vegetative + Generative cells) --(Pollination)--> lands on Stigma --(Germination)--> Pollen Tube --(Generative cell Mitosis)--> 2 Male Gametes --(Enters Synergid)--> Syngamy (with Egg) & Triple Fusion (with 2 Polar Nuclei).
22. Formulating a Hypothesis: Desert seed germination. Answer:
23. Analyzing & Redesigning: Urban allergies (All-male trees). Answer:
/Class-12/Question-Bank/Competency-Based/Unit_1_Chapter_1_Sexual_Reproduction_in_Flowering_Plants_Competency_Questions.mdx