Ans: Reproduction is the biological process by which organisms produce new individuals of the same species to ensure continuation of the species.

Ans: Vegetative propagation and budding are two modes of asexual reproduction in plants.

Ans: Pollination is the transfer of pollen grains from the anther of a flower to the stigma of the same or another flower.

Ans: Fertilisation is the fusion of the male gamete (pollen) with the female gamete (egg cell) inside the ovule to form a zygote.

Ans: Self-pollination: transfer of pollen from the anther to the stigma of the same flower or another flower on the same plant. Cross-pollination: transfer of pollen from the anther of one plant to the stigma of a flower on a different plant of the same species, aided by wind, water, or insects.

Ans: Vegetative propagation is a type of asexual reproduction in which new plants grow from vegetative parts like roots, stems, or leaves. Examples: (1) Potato grows from its tubers (stem). (2) Rose grows from stem cuttings.

Ans: Asexual reproduction: involves only one parent, no gamete formation, offspring are genetically identical (clones), e.g., budding in yeast. Sexual reproduction: involves two parents, formation and fusion of gametes, offspring show genetic variation, e.g., seed formation in flowering plants.

Ans: A flower has: (1) Sepals – protect the flower bud. (2) Petals – attract pollinators. (3) Stamens (male) – each has an anther (produces pollen) and filament. (4) Pistil (female) – has stigma (receives pollen), style, and ovary (contains ovules with egg cells). After pollination, pollen tube grows through the style to deliver the male gamete to the ovule for fertilisation, forming a seed inside the fruit (ripened ovary).

Ans: Advantages of sexual reproduction: (1) Produces genetic variation due to mixing of genes from two parents, which helps in adaptation and evolution. (2) Variations allow populations to survive changing environments. (3) Harmful mutations can be eliminated when offspring with unfavourable traits do not survive. Asexual reproduction only clones the parent, so a single disease can wipe out the entire population.

Ans: Seed germination is the process by which a seed develops into a seedling. Process: The seed absorbs water (imbibition), the embryo becomes active, the radicle (future root) emerges first, followed by the plumule (future shoot). The seedling grows using food stored in cotyledons. Conditions required: (1) Water – for metabolic activity and softening the seed coat. (2) Oxygen – for aerobic respiration to provide energy. (3) Suitable temperature – for enzyme activity (usually 25–35°C). (4) Light – needed by some seeds (e.g., lettuce) but not all. Factors that inhibit germination: hard seed coats, dormancy, and lack of water or oxygen.

Ans: Reproduction ensures the continuity of a species by producing new individuals. Without reproduction, a species would eventually become extinct. It also helps in maintaining population numbers and, in sexual reproduction, introduces genetic variation essential for evolution.

Ans: Hydra and yeast reproduce by budding. In both, a small outgrowth (bud) develops on the parent body, grows, and eventually detaches to form a new independent organism.

Ans: Fertilization is the fusion of a male gamete (sperm) with a female gamete (ovum/egg) to form a zygote. In humans, fertilization usually occurs in the fallopian tube (oviduct).

Ans: External fertilization: (1) Fusion of gametes occurs outside the body of the female. (2) Large number of gametes released. (3) Requires water as medium. (4) Less parental care; high mortality. Examples: frogs, fish, most aquatic animals. Internal fertilization: (1) Fusion of gametes occurs inside the body of the female. (2) Fewer gametes released. (3) Does not require external water. (4) Greater parental care; higher survival rate. Examples: reptiles, birds, mammals (including humans).

Ans: Vegetative propagation is a type of asexual reproduction in plants in which new plants develop from vegetative parts (roots, stems, or leaves) rather than seeds. The offspring are genetically identical to the parent plant. Examples of artificial vegetative propagation: (1) Cutting — a piece of stem is cut and planted in moist soil; roots develop and a new plant grows; e.g., rose, sugarcane. (2) Grafting — the stem of one plant (scion with desired characteristics) is joined to the rooted stem of another plant (rootstock); used for mango, apple to get seedless or better-quality fruits.

Ans: Pollination is the transfer of pollen grains from the anther of a stamen to the stigma of a carpel. Self-pollination: (1) Pollen is transferred to stigma of the same flower or another flower on the same plant. (2) No genetic variation produced. (3) Examples: wheat, pea, tomato. Cross-pollination: (1) Pollen is transferred from flowers of one plant to the stigma of flowers of another plant of the same species. (2) Produces genetic variation in offspring. (3) Requires agents like wind, water, insects or birds. Examples: sunflower, maize.

Ans: Methods of asexual reproduction: (1) Binary fission — parent body divides into two daughter cells; e.g., Amoeba, Paramecium, bacteria. (2) Multiple fission — parent divides into many daughter cells simultaneously; e.g., Plasmodium (malarial parasite). (3) Budding — a small outgrowth (bud) forms on parent body, grows and detaches; e.g., Hydra, yeast. (4) Spore formation — microscopic spores formed in sporangia; released and germinate in suitable conditions; e.g., Rhizopus (bread mould), ferns. (5) Fragmentation — parent breaks into pieces, each piece grows into a new organism; e.g., Spirogyra (algae). (6) Regeneration — if organism is cut into pieces, each piece can form a new organism; e.g., Planaria, Hydra. (7) Vegetative propagation — new plants from vegetative parts; e.g., Bryophyllum from leaves.

Ans: Fertilization in humans: The male releases millions of sperms into the female reproductive tract during intercourse. Sperms swim through the cervix and uterus into the fallopian tube. If a mature ovum (released from ovary during ovulation) is present, one sperm penetrates it and fuses to form a zygote. The zygote contains 46 chromosomes (23 from each parent). Embryo development: (1) Zygote undergoes rapid cell division (cleavage) to form a ball of cells called morula. (2) Further division forms blastocyst (hollow ball). (3) Blastocyst implants into the uterine wall (endometrium) — implantation. (4) Placenta develops — connects embryo to mother; supplies oxygen, nutrients and removes CO2 and waste via mother's blood. (5) Embryo develops all organs over ~9 months (gestation period). (6) At birth, the fully developed baby (foetus) is delivered through the vagina.

Ans: Asexual reproduction: one parent; no gametes; no fertilization; offspring genetically identical (clones); no variation; faster; requires less energy; e.g., bacteria, Hydra, Amoeba. Sexual reproduction: two parents (usually); gametes formed by meiosis; fertilization occurs; offspring genetically different from parents; genetic variation present; slower; requires more energy; e.g., humans, frogs, flowering plants. Significance of sexual reproduction for evolution: (1) Meiosis (gamete formation) and fertilization introduce enormous genetic variation. (2) Variation provides raw material for natural selection — individuals better adapted to the environment survive and reproduce. (3) Over many generations, accumulated variation leads to formation of new species (speciation). (4) A genetically varied population is less vulnerable to extinction — if one variant is killed by a disease or environmental change, other variants may survive. (5) Asexual populations (all identical) can be wiped out entirely by a single pathogen. Thus, the variation produced by sexual reproduction is the engine of evolutionary change.

Ans: Male reproductive system: (1) Testes — primary sex organs; located in scrotal sac outside body (lower temperature needed for sperm production); produce sperms and hormone testosterone. (2) Epididymis — stores and matures sperms. (3) Vas deferens — tube carrying sperm from epididymis to urethra. (4) Seminal vesicles and prostate gland — produce secretions that form seminal fluid (nourishes sperms). (5) Urethra — common passage for urine and semen. (6) Penis — copulatory organ; deposits semen in female. Female reproductive system: (1) Ovaries — produce eggs (one per month, alternately); secrete oestrogen and progesterone. (2) Fallopian tubes (oviducts) — carry egg from ovary to uterus; site of fertilization; lined with ciliated cells to move egg. (3) Uterus (womb) — pear-shaped; site of implantation and fetal development; endometrium (inner lining) thickens each month for implantation. (4) Cervix — narrow lower part of uterus connecting to vagina. (5) Vagina — birth canal; receives penis during intercourse.