• Pollination: Pollen grains travel from the anther to the stigma (by wind, insects, water or birds).
• Pollen germination on stigma: The pollen grain lands on a compatible stigma and produces a pollen tube that grows down through the style into the ovary.
• Fertilisation: The male gamete (sperm cell) travels through the pollen tube and fuses with the egg cell (female gamete) inside the ovule.
• Formation of zygote: The fusion of egg + sperm produces a zygote, which later develops into an embryo (and eventually the seed).

• Explanation of Assertion (A) FALSE: The zygote does NOT immediately attach to the uterus wall. After fertilisation (which happens in the oviduct/fallopian tube), the zygote undergoes several rounds of mitotic cell division while slowly travelling through the oviduct towards the uterus. Only after reaching the uterus does implantation happen. So the process is not “immediate”.
• Explanation of Reason (R) TRUE: The uterus does prepare itself. After ovulation (around day 14 of the menstrual cycle), the uterus lining (endometrium) becomes thick, soft and rich in blood vessels – all in preparation to receive and nourish a fertilised egg. So the uterus wall is indeed prepared.

• Only one parent involved: In asexual reproduction, a single parent produces offspring. There is no mixing of genetic material from two different individuals.
• Based on Mitosis: The central process is mitosis – a type of cell division where the parent cell divides to produce two daughter cells, each with the exact same number and type of chromosomes as the parent. No chromosome shuffling or recombination occurs.
• No gametes or fertilisation: Gametes (sperm/egg) are not formed, so there is no random combination of chromosomes from two parents. Every new cell is an exact copy of the parent cell’s DNA.

• Fertilisation has occurred: When a sperm fertilises the egg, a zygote forms, which implants into the thickened uterine lining. The lining is now being used – it does not need to be shed.
• Hormonal changes: After implantation, the body releases hormones (such as human chorionic gonadotropin — hCG) that signal the ovaries to stop releasing new eggs. Without a new egg being released, the next ovulation cycle does not begin.
• Uterine lining is maintained: The thickened, blood-vessel-rich uterine lining is maintained throughout pregnancy to nourish the growing embryo/foetus. Since it is not shed, menstruation does not occur.

• Night-blooming flowers and white/pale colour: At night, there is no sunlight. Colours that are bright or vibrant during the day (reds, blues, purples) are not easily visible in darkness. However, white or light-coloured flowers reflect even small amounts of moonlight or starlight, making them visible to nocturnal pollinators such as moths, bats and some beetles.
• Day-blooming flowers and bright colours: During daylight, pollinators like bees, butterflies, and birds can see a full range of colours. So day-blooming flowers use vivid colours (yellow, red, purple, orange) to attract these pollinators.
• Additional factor: fragrance: Night-blooming flowers often compensate for reduced visibility by producing stronger fragrances. Moths, for example, are strongly guided by scent in the dark.

• No genetic variation: Since all plants are genetically identical, if the parent plant has no resistance to a particular disease or pathogen, none of the offspring will have it either. The entire crop becomes equally susceptible.
• No new combinations of genes: Sexual reproduction produces offspring with new gene combinations through meiosis and fertilisation. Some of these combinations may confer resistance to new diseases. Vegetatively propagated plants miss out on this advantage.
• Disease can spread rapidly: If one plant in a genetically uniform crop is infected, the pathogen can easily spread to all plants since all plants have the same susceptibility. There are no “resistant” individuals to slow the spread. Example: The Irish Potato Famine (1845) was partly because potato crops were grown by vegetative propagation, leading to genetically uniform plants that were all equally vulnerable to the Phytophthora blight.

1. Reduced genetic variation: In self-pollination, no new genetic material from another individual enters the gene pool. The offspring inherit genetic material only from one parent plant. Over generations, the population becomes genetically more and more uniform.
2. Inbreeding depression: Repeated self-pollination over many generations causes inbreeding. This increases the chances that offspring will receive two copies of the same harmful recessive gene (one from each side of the same parent), potentially expressing genetic disorders or weaknesses. This is called inbreeding depression and leads to weaker, less fit plants.
3. Reduced adaptability: Genetic diversity is the raw material for evolution and adaptation. A genetically uniform population has a very limited range of traits. If the environment changes (new disease, climate shift, new pest), the entire population may lack the variation needed to survive. This could lead to extinction.
4. No new trait combinations: Sexual reproduction with cross-pollination creates new combinations of characters through meiosis (assortment of chromosomes) and fertilisation. With only self-pollination, these new combinations are not generated and evolution slows down dramatically.
5. Short-term advantage, long-term risk: Self-pollination can be advantageous in the short term (especially if pollinators are absent), but over many generations, the lack of genetic diversity makes the species highly vulnerable.

• Method 1: Cutting A stem cutting from the parent plant is placed in soil. The cutting grows roots and develops into a new plant with the same genetic material. Effective because: It is simple, fast and produces a plant identical to the parent. Used for roses, sugarcane, money plant, etc.
• Method 2: Grafting A stem piece (scion) from a desired plant is joined onto the rooted stem (rootstock) of another plant. The two parts unite and grow as one plant. Effective because: It preserves the desired characteristics (taste, yield) of the parent. Used for mango, apple, citrus.
• Method 3: Layering A branch of the parent plant is bent and the middle portion is buried in soil. It develops roots while still attached, then is cut and grown independently. Effective because: The new plant develops while still receiving nourishment from the parent, making survival very high.
• Method 4: Tissue Culture (Most Efficient) Small pieces of plant tissue (from the shoot tip/apical meristem) are placed in a sterile nutrient medium in a laboratory. Hundreds of genetically identical plantlets can be grown from one parent plant. Effective because: It produces thousands of clones very quickly, year-round, in a small space and the plants are disease-free. This has revolutionised farming, especially for banana cultivation.

• Hypothesis 1: Pollen germination rate varies with different sugar concentrations – i.e., some concentration is better than others for germination.
• Hypothesis 2: There is an optimal sugar concentration at which maximum pollen germination occurs.
• Hypothesis 3: Very high or very low sugar concentrations inhibit pollen germination (either too little energy/nutrients or osmotic stress).
• Hypothesis 4: Pollen tube length/growth rate increases (or decreases) as sugar concentration increases.
• Hypothesis 5: A minimum sugar concentration is necessary for germination – at 0% (plain water), pollen will not germinate.

(ii) Parameters (variables) to be kept the same (controlled variables):

• The type of pollen used – same species, same flower, collected at the same time.
• The amount/volume of pollen grains placed on each slide.
• Temperature – all slides kept at the same temperature, as temperature affects germination.
• Humidity/moisture conditions — same environment for all slides.
• Time of observation – germination is checked at the same time interval for all slides.
• The type of sugar used (e.g., sucrose in all) – only concentration should vary.
• The volume of solution on each slide should be equal.
• Light conditions – all slides kept under the same lighting.

1. Plant: Tomato. Observation: Stamens cover the stigma. Type of Pollination: Self-Pollination. Reason: Since the stamens (which produce pollen) physically surround and cover the stigma (which receives pollen), pollen can very easily fall directly onto the stigma of the same flower. This strongly favours self-pollination (autogamy).
2. Plant: Wheat. Observation: Flowers open after pollination. Type of Pollination: Self-Pollination (Cleistogamy). Reason: In wheat, pollination occurs while the flower is still closed (before it opens). This is called cleistogamy. Pollen from the anthers fertilises the stigma of the same closed flower – a guaranteed form of self-pollination. Wind pollination for cross-pollination is also possible in wheat when it opens, but self-pollination is the primary mechanism.
3. Plant: Papaya. Observation: Male and female flowers on different trees. Type of Pollination: Cross-Pollination (obligatory). Reason: Papaya is a dioecious plant – male flowers (with stamens/pollen) and female flowers (with pistil) are on separate trees. Since the pollen source (male tree) and the egg (female tree) are on different plants, cross-pollination by an external agent (usually insects) is the only option. Self-pollination is impossible.

• Hypothesis 1: Adding a bee colony to apple orchards increases the rate of pollination, which in turn increases fruit set percentage.
• Hypothesis 2: Better pollination (through bees) reduces premature fruit drop, because well-fertilised fruits develop more completely.
• Hypothesis 3: Mixed farming with beekeeping can compensate for the declining population of natural pollinators in the region and improve apple yield.

(ii) Parameters in the experiment:

• Independent variable (what changes): Pollination method – Natural pollination (Place A) vs. Mixed farming with bee colony (Place B).
• Dependent variables (what is measured): Fruit set percentage (number of fruits formed / total fruit-bearing branches × 100) and fruit drop percentage (premature falling of fruits).
• Controlled variables (kept same): Apple variety, location conditions (both in Himalayan region), time of experiment, size of orchard, care and irrigation practices.

(iii) Comparison and Analysis:
Based on the data shown in the bar graph:

• Place B (with bee colony) shows significantly higher fruit set percentage compared to Place A (natural pollination). This means more flowers successfully converted into fruits where bees were present.
• Place B shows significantly lower fruit drop percentage compared to Place A. When fruits are properly pollinated and fertilised, they develop fully and do not fall off prematurely.
• Place A has lower fruit set and higher fruit drop, reflecting the problem of insufficient pollinators in the wild Himalayan habitat.

Overall, Place B demonstrates a far higher effective apple yield per orchard compared to Place A.
(iv) Inference from the data:
Introducing a bee colony through mixed farming significantly improves pollination efficiency in apple orchards. This leads to higher fruit set and lower premature fruit drop, resulting in better apple yields. The data supports the hypothesis that the decline in natural pollinators is a major cause of declining apple yield in the Himalayan region, and that beekeeping is an effective, sustainable solution to this problem. It also highlights the crucial ecological role of pollinators in agricultural productivity.

1. The menstrual cycle length varies among individuals: The textbook states that the cycle repeats “typically every 21–35 days (often around 28 days)”. Day 14 is approximately the midpoint of a 28-day cycle, and ovulation tends to occur at the midpoint. However, for a person with a 21-day cycle, ovulation may happen around day 7, and for a 35-day cycle, ovulation may happen around day 21. Saying “always day 14” ignores this natural variation.
2. Even in the same individual, cycle length and ovulation day can vary: Factors like stress, illness, significant weight change, travel, sleep disturbance, and hormonal imbalances can shift the timing of ovulation in any given month. A person who usually ovulates on day 14 might ovulate on day 11 or day 17 in a different month.
3. The “day 14” rule is based on the idealized 28-day cycle: It is a generalisation used for educational purposes and approximate family planning. Medical professionals and researchers acknowledge that actual ovulation day is variable and can only be reliably confirmed through methods like tracking basal body temperature, monitoring cervical mucus, or using ovulation predictor kits.

• Cutting: A stem segment is cut, stripped of leaves on the lower half and planted at an angle in soil mixed with compost. Roots develop from the nodes. Examples: money plant, sugarcane, rose.
• Grafting: A stem piece (scion) from one plant (Plant B) is inserted into a slit made in a rooted plant (Plant A, the stock) of another variety. Both join and grow together. It is used to combine desirable qualities of two varieties – for example, grafting a high-yield rose variety onto a disease-resistant root stock. Farmers learn modern grafting through Krishi Vigyan Kendras (KVKs).
• Layering: A flexible twig of a plant (e.g., lemon) is bent and buried partially in soil while still attached to the parent. Roots develop in 10–15 days. The rooted twig is then cut from the parent and grows independently.
• Tissue Culture: Tiny pieces of shoot tip (apical meristem) are grown on sterile artificial nutrient media in a laboratory. Thousands of genetically identical, virus-free plantlets are produced rapidly. This has revolutionised banana farming by providing mass-produced healthy plantlets.
• Natural vegetative propagation: Potato and ginger sprout from fleshy underground stems; Bryophyllum leaves sprout tiny plantlets from their margins.

In Simple Animals and Fungi:

• Budding (Yeast and Hydra): In yeast, a small outgrowth (bud) forms on the parent cell, enlarges and separates. In hydra, repeated cell division at a specific site produces a bud that grows and detaches to live independently. Multiple buds can form simultaneously on one hydra.
• Spore Formation (Fungi): Moulds like Rhizopus and Aspergillus produce millions of lightweight, single-celled spores in sac-like structures (sporangia) or on swollen vesicles on hyphae. Spores disperse through air and germinate rapidly when they land on moist, nutrient-rich surfaces.

Common Cellular Basis — Mitosis:
All methods of asexual reproduction are ultimately driven by mitosis – a type of cell division that produces two daughter cells each having the same number of chromosomes as the parent cell. Because only one parent’s DNA is involved, all offspring are genetically identical to the parent and to each other – they are called clones. This method is fast and allows rapid population increase under favourable conditions, but creates no genetic variation.

• Self-pollination: Pollen reaches the stigma of the same flower or the same plant. It is reliable but produces no variation.
• Cross-pollination: Pollen is transferred from the anther of one plant to the stigma of another plant of the same species, aided by pollinators. It creates genetic variation.

Pollination Strategies:
Nature has evolved diverse pollination strategies depending on the pollinator:

• Wind pollination (wheat, maize, rice): Light, smooth pollen produced in millions; long feathery stigmas trap them. Wind-pollinated plants produce vastly more pollen (5–10 lakh grains per flower) but achieve fewer seeds (50–200).
• Insect pollination (sunflower, hibiscus, marigold): Flowers are brightly coloured, fragrant, and nectar-producing; pollen is large and sticky; stigma is sticky. Fewer pollen grains (20,000–40,000) but more seeds formed (800–1,000) due to higher efficiency.
• Water pollination (Vallisneria, Hydrilla): Water currents carry pollen between aquatic flowers. Bird pollination (coral tree, hibiscus): Birds like sunbirds and Indian white-eyes carry pollen while collecting nectar.

Fertilisation:
Once pollen lands on a compatible stigma, it germinates and produces a pollen tube that grows down through the style into the ovary. The male gamete travels through this tube and fuses with the egg cell in the ovule. This fusion of gametes is fertilisation, forming a zygote.
Seed and Fruit Formation:
The fertilised zygote develops into an embryo. The ovule develops into a seed, while the ovary wall enlarges and develops into a fruit surrounding the seeds. Seeds are dispersed by wind, water or animals. When conditions (water, warmth, air) are favourable, the seed germinates and grows into a new plant.
Importance of Genetic Variation:
Cross-pollination introduces new combinations of genetic characters in offspring. This variation helps plant populations adapt to changing environments, resist diseases, and evolve. In contrast, exclusively self-pollinating populations gradually lose genetic diversity, becoming more vulnerable to disease and environmental change. Plant breeders exploit cross-pollination through artificial hybridisation to develop high-yielding and disease-resistant varieties.

• Testes (singular: testis): Two oval-shaped organs located in the scrotum outside the body. The scrotum keeps the testes cooler than body temperature, which is essential for sperm production. The testes also secrete male hormones that control sperm production and trigger puberty changes in boys.
• Vas deferens: A long tube through which sperm travel from the testes toward the urethra.
• Seminal vesicles and Prostate gland: These accessory glands add fluids that nourish sperm, keep them active and aid movement.
• Urethra: A common passage for both urine and sperm; opens outside through the penis.
• Sperm structure: Each sperm has a head (containing 23 chromosomes of genetic material) and a long tail that helps it swim toward the egg.

Sperm are produced in millions, are actively motile and contain no stored nutrients.
Female Reproductive System:
The female reproductive system produces eggs, provides the site for fertilisation and nourishes the developing baby. Its major components are:

• Ovaries: A pair of organs that produce egg cells (female gametes) and secrete female hormones. At birth, a girl’s ovaries contain millions of immature eggs.
• Fallopian tubes (Oviducts): Connect each ovary to the uterus. The egg is released into the oviduct during ovulation, and fertilisation typically occurs here.
• Uterus: A muscular, bag-like organ where the fertilised egg implants and the foetus develops during pregnancy.
• Cervix: The narrow passage connecting the uterus to the vagina.
• Vagina: The birth canal and entry point for sperm.

From Gamete Formation to Implantation:
The process of gamete formation (gametogenesis) occurs through meiosis in the gonads. In males, millions of sperm are produced continuously. In females, from puberty onward, usually one mature egg is released from an ovary every month (ovulation, ~day 14 of the cycle).
During sexual intercourse, millions of sperm enter through the vagina, swim through the uterus, and reach the egg in the oviduct. When a sperm successfully fuses with the egg, a zygote is formed – with 23 + 23 = 46 chromosomes restored. The zygote undergoes repeated mitotic divisions while travelling down to the uterus. It then implants into the thickened inner lining of the uterus, which has developed a rich blood supply in preparation. This implantation marks the beginning of pregnancy.

• Phase 1: — Menstruation (Days 1–5): The cycle begins on day 1 when menstruation starts. The thick, blood-vessel-rich inner lining of the uterus (endometrium), which was built up in the previous cycle to receive a possible zygote, sheds. This lining, along with blood, passes out through the vagina. Menstruation usually lasts 3–7 days.
• Phase 2: Follicular/Rebuilding Phase (Days 6–14): After menstruation, the uterine lining gradually rebuilds itself. Simultaneously, an egg begins maturing inside the ovary under the influence of hormones.
• Phase 3: Ovulation (Day ~14): A mature egg is released from one ovary into the fallopian tube. This is called ovulation. The egg travels toward the uterus. It remains viable for fertilisation for approximately one day.
• Phase 4: Luteal/Secretory Phase (Days 15–28): The uterine lining continues to thicken and fill with blood vessels, preparing to receive and nourish a fertilised egg. If no fertilisation occurs by approximately day 28, the lining starts breaking down and the next menstruation begins, restarting the cycle.

If Fertilisation Occurs:
When a sperm fuses with the egg in the oviduct, a zygote is formed. The zygote divides repeatedly and travels to the uterus, where it implants into the prepared uterine lining. Once implantation occurs, the menstrual cycle stops for the duration of pregnancy (~9 months). The uterine lining is maintained to support and nourish the growing embryo and foetus.
If Fertilisation Does Not Occur:
The egg degenerates within about a day. The thickened uterine lining is no longer needed and breaks down. Menstruation occurs (days 1–5 of the next cycle), and the entire cycle repeats.
This cycle, regulated by hormones from the ovaries and pituitary gland, is a hallmark of a healthy female reproductive system. Menstruation is a normal, healthy process – not something to be ashamed of – and requires clean menstrual hygiene practices.

• External Fertilisation: In many aquatic animals (frogs, most fish), the female releases eggs into water and the male releases sperm over them. Fertilisation occurs outside the body. Key features:
  • Very large numbers of eggs are produced (frogs: 5,000–50,000; fish: 100s–1,000s) because many are lost to water currents, predators, and environmental hazards.
  • Survival rate of young ones is low.
  • Larvae hatch from eggs and pass through intermediate feeding stages before transforming into adults (e.g., tadpole → frog; caterpillar → butterfly).
• Internal Fertilisation: In reptiles, birds, and mammals (including humans), sperm are deposited inside the female body, where they fertilise the egg. Key features:
  • Far fewer eggs are produced (lizards: 2–20; birds: 1–15) because each is protected and nourished much better. Survival rate is moderate to high.
  • Reptiles and birds lay eggs with sufficient yolk to nourish the embryo until hatching. Mammals (including humans) retain the developing embryo inside the mother’s uterus.

Human Pregnancy – Three Trimesters:
Human pregnancy lasts approximately nine months and is divided into three trimesters:

1. First Trimester (Months 1–3): The fertilised egg (zygote) divides and develops into an embryo during the first two months. Major organs — brain, heart, limbs, eyes — begin forming. From about the ninth week, the developing embryo is called a foetus. This is the most critical period; the mother must avoid harmful substances (alcohol, certain medicines) and ensure good nutrition.
2. Second Trimester (Months 4–6): The foetus grows bigger and stronger. The mother can usually feel its movements. Organ systems continue developing. The foetus develops recognisable human features.
3. Third Trimester (Months 7–9): The baby grows rapidly, gains weight, and gets ready for independent life outside the womb. The brain and lungs mature. At the end, strong uterine contractions push the foetus out through the birth canal during childbirth.

Importance of Maternal Health:
A mother’s physical and emotional health during pregnancy directly affects the baby’s growth and safety:

• She should eat a balanced diet rich in proteins, vitamins, iron, and calcium.
• Regular medical check-ups are essential to monitor foetal development and the mother’s health.
• She must avoid harmful substances — smoking, alcohol, and unprescribed medicines can cause birth defects.
• Adequate rest and light exercise, as advised by the doctor, support a healthy pregnancy.
• Emotional well-being and family support reduce stress, which benefits both mother and baby.
• Breastfeeding after birth provides complete nutrition and immunity to the newborn.
• Post-partum depression (anxiety and fatigue after delivery) is a recognised, treatable condition — mothers experiencing it should consult healthcare workers such as doctors or ASHA workers.

India’s more than 10 lakh ASHA (Accredited Social Health Activist) workers play a vital role in promoting maternal care, safe deliveries, hygiene, and family planning across rural communities under the National Health Mission.