Ans: Flower is the reproductive organ of angiosperms. Male part — Stamen: anther (produces pollen) + filament. Female part — Carpel: stigma + style + ovary (with ovules). Pollination: transfer of pollen from anther to stigma. Self-pollination (same flower/plant) or cross-pollination (different plants, by wind/insects/water). After landing on stigma, pollen germinates — pollen tube grows through style carrying two male gametes. Fertilisation: one male gamete fuses with egg → zygote (future embryo); other male gamete fuses with polar nuclei → endosperm (nutrition for seed) — called double fertilisation, unique to angiosperms. Ovule → seed; ovary → fruit.

Ans: Binary fission: organism divides into two equal halves. Example: Amoeba, Bacteria. Budding: a bud forms on parent body and grows into new organism. Example: Hydra (animal), Yeast (fungus). Spore formation: light, tiny spores are produced that germinate into new organisms. Example: Rhizopus (bread mould). Fragmentation: organism breaks into pieces, each grows into a new individual. Example: Spirogyra (alga). Vegetative propagation: new plant grows from vegetative parts — stem (potato tubers), leaf (Bryophyllum), root (sweet potato). Regeneration: organism regenerates from fragments. Example: Planaria (flatworm).

Ans: Hydra reproduces asexually by budding. A small outgrowth (bud) develops on the side of the parent body. Cells in the bud divide by mitosis and form a miniature Hydra. When the bud is fully formed with a mouth and tentacles, it detaches from the parent and lives independently. Hydra can also reproduce sexually: sperm are released into water and fertilise eggs on another Hydra; the fertilised egg (zygote) develops into a new Hydra. Hydra also has remarkable regeneration ability — a small piece can grow into a complete organism.

Ans: The menstrual cycle is a monthly (~28-day) cycle in females of reproductive age. Day 1–5: Menstruation — uterine lining (endometrium) sheds as blood (if no fertilisation occurred). Day 6–13: Follicular phase — oestrogen causes endometrium to thicken; an egg matures in the ovary. Day 14: Ovulation — mature egg released from ovary. Day 15–28: Luteal phase — progesterone maintains thickened endometrium in preparation for embryo. If fertilisation does not occur, progesterone levels fall, endometrium breaks down, and menstruation begins again. The cycle prepares the uterus for a possible pregnancy every month.

Ans: Variation is the raw material for evolution. Organisms with variations that are better suited to their environment are more likely to survive and reproduce (natural selection). Sexual reproduction creates variation because: (1) It combines genetic material from two different parents. (2) During meiosis, chromosomes exchange segments (crossing over), creating new gene combinations. (3) Random fertilisation of different sperm and eggs further increases diversity. This means offspring are never identical to each other or to their parents, increasing adaptability of the species to changing environments.

Ans: Deoxyribonucleic acid.

Ans: The ovary develops into the fruit, and the ovule develops into the seed.

Ans: In the fallopian tube (oviduct).

Ans: Regeneration is the ability of an organism to grow a complete new individual from a cut or broken body piece. Examples: Planaria and Hydra.

Ans: Hydra and yeast.

Ans: The testes produce sperms (male gametes) and the male hormone testosterone.

Ans: Sperm formation requires a temperature lower than the normal body temperature. The scrotum keeps the testes about 2–3°C cooler than the inside of the body.

Ans: Pollination is the transfer of pollen from the anther to the stigma of a flower; it occurs outside the ovule. Fertilisation is the fusion of the male gamete with the egg (female gamete) to form a zygote; it occurs inside the ovule in the ovary. Pollination precedes fertilisation.

Ans: It involves only one parent, no gametes are formed and no fusion of gametes occurs. The two daughter cells are genetically identical to the parent.

Ans: Unisexual flowers contain either stamens or carpels but not both, e.g. papaya and watermelon. Bisexual flowers contain both stamens and carpels, e.g. hibiscus and mustard.

Ans: Binary fission: one parent cell divides into two daughter cells; occurs in favourable conditions; e.g. Amoeba, Leishmania. Multiple fission: one parent cell divides into many daughter cells simultaneously; often occurs inside a cyst under unfavourable conditions; e.g. Plasmodium. In both cases the nucleus divides first.

Ans: Rhizopus has thread-like hyphae. Some hyphae grow upright and bear round sporangia at their tips, which contain hundreds of spores. Spores have a tough protective covering and remain viable under unfavourable conditions. When the sporangium bursts, the spores are carried by air and on landing on a moist, suitable surface germinate and grow into new Rhizopus. Spore formation is an asexual method.

Ans: Barrier: a condom prevents sperms from reaching the egg and also protects against sexually transmitted infections. Chemical: oral contraceptive pills change the hormonal balance so that eggs are not released. Surgical: vasectomy (blocking the vas deferens) in males or tubectomy (blocking the fallopian tubes) in females stops the gametes from meeting.

Ans: A flower has sepals (outermost, green, protect the bud), petals (coloured, attract insects for pollination), stamens (male part; the anther produces pollen grains containing male gametes; the filament supports the anther) and the carpel or pistil (female part). The carpel has the stigma (sticky tip that receives pollen), style (tube that connects stigma to ovary) and ovary (swollen base containing ovules; each ovule has an egg cell). After fertilisation, the ovule becomes the seed and the ovary becomes the fruit.

Ans: Male: testes (produce sperms and testosterone, located in the scrotum for a lower temperature), vas deferens (carries sperms), seminal vesicles and prostate gland (add fluids to nourish and carry the sperms, forming semen), urethra (common passage for urine and semen) and penis. Female: ovaries (produce eggs and hormones), fallopian tubes (carry the egg; fertilisation occurs here), uterus (where the embryo implants and develops), cervix and vagina (birth canal). The placenta supplies nutrition to the foetus during pregnancy.