Ans: Vegetative propagation is a type of asexual reproduction in which new plants arise from the vegetative parts of a parent plant — such as stems, roots, or leaves — without the formation of seeds. Since it involves only one parent, the offspring are genetically identical to the parent. Examples: Potato and ginger sprout new plants from their fleshy underground stems, and Bryophyllum develops tiny plantlets along the edges of its leaves.

Ans: Budding is a type of asexual reproduction in which repeated cell division at a specific site on the parent’s body produces a small outgrowth called a bud. The bud gradually enlarges and eventually separates from the parent to live independently as a new individual. In hydra, one can often observe many buds growing on the parent’s body simultaneously. This is an example of asexual reproduction in a multicellular animal.

Ans: Mould grows from spores present in the air. These spores are lightweight, usually single-celled structures that float through air currents and settle on moist surfaces. However, spore germination requires warmth and moisture. When bread is kept in a warm, moist environment (25–35°C), the spores find ideal conditions and reproduce rapidly. In a refrigerator, the low temperature slows or completely stops the reproduction of mould. This is why refrigeration is used to preserve perishable food — it prevents the growth of moulds and bacteria by denying them the warmth they need to reproduce.

Ans: The central process behind all asexual reproduction is mitosis — a type of cell division that produces two daughter cells, each having the same number of chromosomes as the parent cell. Because the offspring receive an exact copy of the parent’s genetic material, they are genetically identical to the parent. Such genetically identical offspring are called clones. This method is fast and helps organisms increase their population rapidly, especially when environmental conditions are favourable.

Ans: The horticulturist should use grafting. In grafting, a healthy rooted plant (Plant A, e.g., a wild rose) is taken and a slit or wound is created on one of its twigs. A stem cutting from a different variety (Plant B, e.g., a yellow or pink rose) is then inserted and fitted into this slit. The wound is covered with cotton cloth or wrapping film to prevent pest entry until it heals, and other branches of Plant A are cut. By grafting stem cuttings from both yellow and pink rose plants onto Plant A, the horticulturist can get all three flower colours on a single plant.

Ans: A complete flower has four parts: sepals, petals, stamen, and pistil. The stamen is the male part of the flower; it consists of a filament and an anther. The anther produces pollen grains that contain the male gametes. The pistil is the female part consisting of three sub-parts — stigma, style, and ovary. The ovary contains ovules, and each ovule has an egg cell (female gamete).

Ans: Self-pollination is the transfer of pollen grains from the anther to the stigma of the same flower or another flower on the same plant. Cross-pollination is the transfer of pollen grains from the anther of a flower on one plant to the stigma of a flower on another plant of the same species. Self-pollination does not require a pollinator, while cross-pollination often depends on external agents such as wind, water, insects, or birds.

Ans: Wheat is wind-pollinated. Its pollen grains are light, small, and produced in very large numbers (5,00,000–10,00,000 per flower). The stigma is long and feathery to trap airborne pollen. Sunflower, on the other hand, is pollinated by insects such as bees and butterflies. Its flowers are brightly coloured, produce nectar, and give off fragrance to attract pollinators. The pollen grains of insect-pollinated plants are large, sticky, or spiny so they can attach to an insect’s body, and the stigma is also sticky. Despite producing far fewer pollen grains, insect-pollinated plants form more seeds per flower (800–1,000 seeds) compared to wind-pollinated grasses (50–200 seeds).

Ans: Fertilisation in plants is the fusion of the male gamete (from the pollen tube) with the female egg cell inside the ovule. After fertilisation, the fertilised egg is called a zygote, which then develops into an embryo. The ovule develops into a seed and the ovary surrounding the ovules enlarges and develops into a fruit. When conditions like water, air, and temperature are favourable, the seed germinates and grows into a new plant.

Ans: Tissue culture is a technique in which plantlets are propagated from the shoot tip (apical meristem) of a selected plant in a controlled laboratory environment. In banana farming, tissue culture provides farmers with mass-produced, healthy plantlets that are free from viruses. This ensures high crop yields and eliminates diseased plants. It is considered asexual reproduction because it involves only one parent plant, and all the plantlets produced are genetically identical to the parent — they are clones. No fusion of male and female gametes takes place.

Ans: Meiosis is a special type of cell division in which the chromosome number of a parent cell (diploid) is reduced to half (haploid) in the daughter cells. These haploid cells are called gametes (sperm and eggs in animals; pollen and egg cells in plants). Meiosis is essential for sexual reproduction because it prevents the chromosome number from doubling in every generation. When two haploid gametes fuse during fertilisation, the chromosome number is restored to the normal diploid number in the resulting zygote.

Ans: (a) Testes: They produce male germ cells called sperm. They are located in the scrotum, which keeps them slightly cooler than body temperature — a condition necessary for sperm formation. The testes also produce a hormone that controls sperm production and causes physical changes during puberty. (b) Vas deferens: It is a long tube through which sperm travel from the testes, ultimately opening into the urethra. (c) Seminal vesicles: These glands add fluids to nourish the sperm and help them remain active and move.

Ans: Ovulation is the process in which one mature egg is released from one of the ovaries, typically occurring around day 14 of the menstrual cycle. Before ovulation, the uterus prepares itself by thickening its inner lining. The released egg travels from the ovary to the oviduct, where it may be fertilised by a sperm. In the given example, if the period started on 1st April, the next period would be expected around 29th April (28 days later), and ovulation would most likely occur around 15th April (approximately day 14 of that cycle).

Ans: Menstruation (or a period) is the process in which the thickened inner lining of the uterus, along with some blood, sheds and leaves the body through the vagina. It occurs when an egg is not fertilised — the lining that had built up to receive a potential zygote is no longer needed and so breaks down. Menstruation usually lasts 3 to 7 days. The full cycle of ovulation, uterus preparation, and menstruation repeats typically every 21–35 days (often around 28 days), beginning at puberty and continuing until menopause (around age 50).

Ans: Frogs use external fertilisation — eggs are released into water and sperm are released over them. Many eggs are destroyed by water currents or eaten by predators, so frogs must produce 5,000–50,000 eggs at a time to ensure some survive. Birds use internal fertilisation, which occurs safely inside the female’s body. After fertilisation, each egg is laid with enough yolk to nourish the developing embryo until it hatches. Because the embryo is well-protected and nourished, the chances of survival are much higher, so birds need to lay only 1–15 eggs. In general, animals with external fertilisation produce more eggs to compensate for greater loss, while internal fertilisation allows fewer eggs with higher survival rates.