Reproduction in Plants and Animals
Reproduction in Plants and Animals
Reproduction gives 2 questions in the Part-III paper and is examined through the modes rather than the biology of any one organism. Naming the mode from an example is the standard format, so learn each mode by its example rather than by its definition alone.
Asexual and Sexual Reproduction
| Point | Asexual | Sexual |
|---|---|---|
| Parents | One | Two |
| Gametes | Not involved | Male and female gametes fuse |
| Offspring | Identical to the parent | Show variation |
| Speed | Fast | Slower |
The key contrast is variation: asexual reproduction produces copies, sexual reproduction produces variation, and variation is what allows a species to adapt. That reasoning is asked more often than the definitions.
Modes of Asexual Reproduction
| Mode | Meaning | Example |
|---|---|---|
| Binary fission | Parent splits into two | Amoeba, bacteria |
| Budding | A bud grows and detaches | Yeast, Hydra |
| Spore formation | Spores germinate into new organisms | Fungi, ferns, moss |
| Fragmentation | Body breaks into pieces that grow | Spirogyra |
| Vegetative propagation | New plant from root, stem or leaf | Potato, ginger, rose, Bryophyllum |
Bryophyllum reproduces from buds on the margins of its leaves, which is the standard leaf example. Potato grows from the eyes of the tuber, and rose and sugarcane from stem cuttings. Vegetative propagation is used commercially because the new plants are identical to the parent and mature faster.
✗ Yeast reproduces by binary fission | ✓ Yeast reproduces by budding; Amoeba uses binary fission
Sexual Reproduction in Plants
Pollination is the transfer of pollen from anther to stigma. Fertilisation is the fusion of the male gamete with the egg. The two are different stages and the words are regularly swapped in options.
- Self-pollination occurs within the same flower or plant.
- Cross-pollination occurs between two flowers of the same kind on different plants.
- Agents of pollination are wind, water, insects and animals.
- After fertilisation the ovary becomes the fruit and the ovule becomes the seed.
- Seeds are dispersed by wind, water, animals and by explosion of the fruit.
Wind-dispersed seeds are light and often winged, as in the drumstick and maple; water-dispersed seeds float, as in the coconut; animal-dispersed seeds have hooks or are eaten with the fruit. Dispersal matters because it prevents overcrowding and lets a species spread — a reason question, not a naming one.
Reproduction in Animals
- Oviparous animals lay eggs — birds, most fish, frogs, reptiles.
- Viviparous animals give birth to young ones — humans, cows, dogs.
- Internal fertilisation happens inside the female body, as in humans and birds.
- External fertilisation happens outside, as in frogs and most fish.
- Metamorphosis is a drastic change of body form — tadpole to frog, caterpillar to butterfly.
Note that the platypus is a mammal that lays eggs, which is the standard exception offered in options. Frogs show both external fertilisation and metamorphosis, which makes them the most examined animal in this topic.
परागण और निषेचन अलग-अलग चरण हैं — पहले परागण, फिर निषेचन।
TRE pointer: Biology is worth about 14 of the 40 science questions in Part-III, and reproduction is a reliable 2 of them. The yeast buds, Amoeba divides pair and the pollination versus fertilisation distinction are the two items asked almost every year. The platypus exception appears whenever oviparous and viviparous are set. With five options and −1/3 for a wrong answer, the mode-and-example table is worth memorising outright.
60-Second Recap
- Asexual reproduction gives identical offspring; sexual reproduction gives variation.
- Binary fission in Amoeba, budding in yeast and Hydra, spores in fungi, fragmentation in Spirogyra.
- Bryophyllum reproduces from leaf margins; potato from tuber eyes.
- Pollination is pollen transfer; fertilisation is the fusion of gametes.
- Ovary becomes the fruit, ovule becomes the seed; dispersal prevents overcrowding.
- Oviparous animals lay eggs, viviparous give birth; the platypus is the mammal exception.
Frequently Asked Questions
What is the difference between pollination and fertilisation?
Pollination is the transfer of pollen grains from the anther to the stigma, and it happens first. Fertilisation is the fusion of the male gamete with the egg inside the ovule, and it happens afterwards. The two terms are regularly swapped in options.
How does yeast reproduce?
By budding. A small outgrowth forms on the parent cell, grows, and eventually detaches as a new individual. Amoeba, by contrast, reproduces by binary fission, splitting into two equal cells. Both examples are set together to test whether the modes are clearly separated.
Why is vegetative propagation used by farmers?
Because the new plants are genetically identical to the parent, so a desirable variety is reproduced exactly, and they usually flower and bear fruit sooner than plants grown from seed. Potato, ginger, sugarcane and rose are all propagated this way commercially.
Which mammal lays eggs?
The platypus, which is the standard exception to the rule that mammals are viviparous. It is offered as an option whenever a question asks candidates to sort animals into egg-laying and live-bearing groups, since most candidates apply the rule without exception.