2. What is pollination? Distinguish between self-pollination and cross-pollination.
Answer
Pollination is the transfer of pollen grains from the anther (male part) of a flower to the stigma (female part) of the same or different flower of the same species.
Feature
Self-Pollination
Cross-Pollination
Transfer
Pollen from anther to stigma of the same flower or another flower on the same plant
Pollen transferred between flowers of different plants of the same species
Agents needed
None (no external agent)
Wind, insects, birds, water
Genetic variation
No variation
Creates variation
Advantage
Guaranteed reproduction even in isolation
Produces varied, often more vigorous offspring (hybrid vigour)
Example
Wheat, pea, rice
Maize, sunflower, mango
Agents of cross-pollination: Wind (anemophily), insects (entomophily), birds (ornithophily), water (hydrophily).
3. Describe the process of fertilisation in flowering plants.
Answer
Fertilisation in plants is the fusion of the male gamete (from pollen) with the female gamete (egg cell in ovule).
Steps: 1. Pollination — Pollen grain lands on the stigma of the pistil 2. Pollen germination — Pollen grain absorbs sugary fluid from stigma and germinates 3. Pollen tube growth — A pollen tube grows down through the style towards the ovary 4. Release of male gametes — Two male gametes travel down the pollen tube into the ovule 5. Double fertilisation (unique to angiosperms):
6. After fertilisation:
One male gamete fuses with the egg cell → forms zygote (2n)
Second male gamete fuses with the secondary nucleus → forms endosperm (3n) — food for developing embryo
Ovule develops into a seed
Ovary develops into a fruit
4. What is vegetative propagation? Give examples and its advantages.
Answer
Vegetative propagation is a form of asexual reproduction in plants where new plants grow from vegetative parts (roots, stems, or leaves) rather than seeds.
Natural vegetative propagation:
Plant part
Examples
Underground stems (tubers)
Potato, yam
Bulbs
Onion, garlic, tulip
Runners/Stolons
Grass, strawberry
Rhizomes
Ginger, turmeric, banana
Leaves
Bryophyllum (buds on leaf margins)
Artificial vegetative propagation:
Cutting — stem cutting planted in soil (rose, sugarcane)
Grafting — joining stem of one plant onto rooted stock (mango, apple)
Layering — bending a stem so it touches soil; roots form before cutting (jasmine)
Tissue culture — growing cells in lab (orchids, banana)
Plants that do not produce viable seeds can be propagated
Earlier flowering and fruiting
5. Explain the process of human reproduction (fertilisation to birth).
Answer
Male reproductive system: Testes produce sperm; sperm travel through vas deferens; mixed with seminal fluid from accessory glands; ejaculated through urethra.
Female reproductive system: Ovaries release egg (ovum) during ovulation; egg travels through the fallopian tube.
Fertilisation:
Occurs in the fallopian tube (oviduct)
One sperm penetrates the egg → zygote (fertilised egg, 2n)
If fertilisation does not occur, egg degenerates
Development: 1. Zygote undergoes cell division (cleavage) → morula → blastocyst 2. Implantation — Blastocyst embeds in the uterine wall (endometrium) — about 7 days after fertilisation 3. Placenta forms — connects mother and embryo; transfers oxygen, nutrients, and removes waste 4. Embryo develops into foetus over 9 months (gestation period) 5. Parturition (birth) — after approximately 40 weeks, the baby is born through the birth canal
6. What is regeneration? Give an example.
Answer
Regeneration is the ability of an organism to regrow lost or damaged body parts.
In simple organisms, entire new individuals can regenerate from fragments.
Planaria (flatworm): If cut into pieces, each piece regenerates into a complete new worm. This is also a form of asexual reproduction called fragmentation.
Hydra: Can regenerate a complete organism from a small piece.
Starfish: Can regrow lost arms; an arm with part of the central disc can regenerate an entire new starfish.
Lizards: Can regrow lost tails (limited regeneration).
Significance: Regeneration involves dedifferentiation (cells revert to stem-cell-like state) and then redifferentiation into specific cell types.
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Frequently Asked Questions
Asexual reproduction: involves only one parent, no gametes, offspring are genetically identical (clones) to the parent. Fast and energy-efficient. Examples: binary fission (Amoeba), budding (Hydra), fragmentation (Planaria), spore formation (fungi), vegetative propagation (plants). Sexual reproduction: involves two parents and gametes (sperm + egg), offspring have genetic variation. Slower but creates diversity — better for adaptation.
