Q1. (b) Budding  ·  Q2. (b) Spore formation  ·  Q3. (b) Self-pollination  ·  Q4. (b) Ovary  ·  Q5. (b) Sperm  ·  Q6. (b) Day 14  ·  Q7. (b) Cervix  ·  Q8. (c) Frog  ·  Q9. (b) Vallisneria  ·  Q10. (b) 46

Q11. (i)  ·  Q12. (i)  ·  Q13. (i)

Q14. Gametogenesis  ·  Q15. Fertilisation  ·  Q16. Seed; fruit  ·  Q17. False. Petals are the coloured parts; sepals are the green outermost whorl.  ·  Q18. True.  ·  Q19. False. Copper-T is an intra-uterine device (a temporary contraceptive placed in the uterus), not a surgical method. Surgical methods include blocking the vas deferens or fallopian tubes.

Q20. (a)–(ii), (b)–(iv), (c)–(i), (d)–(v), (e)–(iii)

Q21. Pollination is the transfer of pollen from the anther to the stigma of a flower. Self-pollination is the transfer of pollen to the stigma of the same flower or another flower of the same plant. Cross-pollination is the transfer of pollen from the anther of one plant to the stigma of a flower on a different plant of the same type.

Q22. A clone is an offspring that is genetically identical to its parent. It is produced by mitosis, the cell division that gives two daughter cells with the same number of chromosomes as the parent cell.

Q23. The scrotum keeps the testes slightly cooler than normal body temperature, which is necessary for sperm formation.

Q24. Seminal vesicles and the prostate gland. The urethra is the common passage for both urine and sperm, carrying sperm from the vas deferens to outside the body.

Q25. In grafting, a healthy stem piece (scion) of a desired variety is inserted into a slit made on the stem of a healthy rooted plant (stock). The wound is wrapped to prevent pests and infection until it heals. It is useful because desirable varieties (e.g., high-yield fruits) can be grown on strong, disease-resistant roots, and the process is quick and reliable for mass propagation.

Q26. In external fertilisation, fusion occurs outside the body (e.g., fish, frog). In internal fertilisation, fusion occurs inside the female body (e.g., lizard, bird, mammal). External fertilisation produces many eggs with low survival; internal fertilisation protects the embryo and gives higher survival.

Q27. Light pollen grains are carried easily by wind over long distances, and producing them in large numbers increases the chance of reaching a stigma. A long, feathery stigma traps the airborne pollen effectively.

Q28. The lining thickens and becomes rich in blood vessels to receive and nourish a fertilised egg (zygote). If the egg is not fertilised, the lining is no longer needed and sheds through the vagina as menstruation.

Q29. Prenatal sex determination is often misused for selective abortion of female foetuses, which leads to an imbalance in the societal sex ratio. Maintaining a healthy sex ratio is essential for a balanced and forward-looking society, so the practice is banned by law.

Q30–Q31. Check your diagrams against Fig. 11.10 (flower) and Fig. 11.19 (female reproductive system) in the textbook. Include all required labels.

Q32. Warmth activates the yeast so it can reproduce and bud quickly. The cotton plug allows air exchange while keeping out dust and contaminating microbes.

Q33. Mould spores need warmth and moisture to germinate and grow. Darkness and avoidance of direct sunlight prevent the bread from drying out and keep conditions favourable for mould growth.

Q34. Fruit formation requires transfer of pollen from the anther to the stigma. Without stamens, no pollen is available, so no fruit forms. Muslin cloth prevents visits by insects and other external agents, so any fruit formed is due to self-pollination within the flower and not cross-pollination.

Q35. (1) Wind: about 2,500 to 20,000 pollen grains per seed (5,00,000 ÷ 200 to 10,00,000 ÷ 50). Insect: about 20 to 50 pollen grains per seed (20,000 ÷ 1,000 to 40,000 ÷ 800). (2) Insect pollination is more efficient, since it needs far fewer pollen grains per seed. (3) Wind-pollinated plants lose most pollen, so producing huge numbers raises the chance that some pollen reaches a stigma, making the strategy effective despite low efficiency.

Q36. (1) Hypothesis: Bee colonies increase fruit set and reduce fruit drop in apple orchards. (2) Independent variable: pollination method (natural vs. bee colony). Dependent variables: fruit set and fruit drop. Controlled parameters: apple variety and orchard conditions such as climate and soil. (3) The bee-colony orchard (Place B) has a higher fruit set (about 40% vs 26%) and much lower fruit drop (about 8% vs 35%), so it gives a higher apple yield. Insect pollinators improve pollination efficiency and reduce premature fruit loss.

Q37. (1) Next period: 28 days after 5 March, which is about 2 April. (2) Ovulation occurs around day 14 of the cycle. Counting day 1 as 5 March, day 14 is about 18 March. (3) The first days of the cycle are menstruation, when the uterine lining is shed. The egg matures in the ovary during the following days, so ovulation happens later in the cycle.

Q38. Sperm form in the testes (gametogenesis; reduced to 23 chromosomes by meiosis) and are stored and transported through the vas deferens, which joins the urethra. Seminal vesicles and prostate add nourishing fluids. Eggs form in the ovaries and are released during ovulation into the oviduct. During intercourse, sperm enter the vagina, travel through the reproductive tract and fuse with the egg in the oviduct to form a zygote. The zygote divides by mitosis while moving to the uterus and implants in the thickened, blood-rich lining, which marks the beginning of pregnancy.

Q39. In hydra, repeated cell division at a specific site forms a small outgrowth called a bud. The bud enlarges and separates from the parent to live independently. In Rhizopus, spores are formed in sac-like structures (sporangia) at the tips of hyphae. When released, the lightweight spores float in air and germinate into new individuals in favourable moist conditions. Comparison: both are asexual, involve a single parent, and produce clones through mitosis. Budding uses a body outgrowth, while spore formation uses tiny, lightweight, numerous reproductive units dispersed by air.

Q40. Barrier methods: condoms and vaginal covers, which stop sperm from reaching the egg. Hormonal methods: oral pills, which change egg release by altering hormones. Intra-uterine methods: Copper-T, placed in the uterus. Surgical methods: blocking the vas deferens (males) or fallopian tubes (females). Condoms act as a physical barrier, so they also reduce the spread of sexually transmitted infections such as HIV, gonorrhoea and syphilis, which pills and IUDs do not prevent.

Q41. Cutting: a shoot piece with nodes is planted in moist soil and grows roots; it is a quick and cheap method (e.g., rose, sugarcane). Layering: a flexible twig is buried while still attached to the parent, develops roots, and is then cut off; it suits plants with flexible stems and gives strong plants. Tissue culture: small plant parts (shoot tips) are grown in nutrient medium; it produces many disease-free plantlets in a short time (e.g., banana).

Q42. The claim is incorrect. (1) The menstrual cycle usually lasts 21 to 35 days, so the timing of ovulation changes between cycles and women. Day 14 is only typical for a 28-day cycle. (2) Ovulation is generally about 14 days before the next period, so in longer or shorter cycles it occurs on a different day. Stress, illness and hormonal changes can also shift the timing.