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Reproduction: How Life Continues – Class 9 Science notes, important questions and MCQs

NCERT Class 9 Science, chapter 11. Notes, key terms, important questions with answers and MCQs.

Chapter overview

Reproduction lets living things produce young ones of their kind. It can be asexual, with a single parent, or sexual, with two parents and gametes.

Asexual reproduction

Binary fission (Amoeba, bacteria), budding (Hydra, yeast), fragmentation (Spirogyra), spore formation (Rhizopus, ferns).
Vegetative propagation in plants: potato (tuber), ginger (rhizome), onion (bulb), Bryophyllum (leaf buds).
Offspring are nearly identical to the parent (clones).

Sexual reproduction

Male and female gametes fuse (fertilisation) to form a zygote.
Plants: flowers carry stamens (male) and pistils (female); pollination brings pollen to the stigma.
Animals: internal fertilisation (humans, birds) or external fertilisation (frogs, fish).
The zygote divides to form an embryo; oviparous animals lay eggs, viviparous give birth.

Key terms

Gamete: a reproductive cell (sperm or egg)
Zygote: the fertilised egg
Oviparous: animals that lay eggs
Viviparous: animals that give birth to young ones

Formulas

Gamete + gamete → zygote → embryo → young one

Important questions with answers

What is the difference between oviparous and viviparous animals?2 marks

Oviparous animals lay eggs that develop outside the body (hen, frog). Viviparous animals give birth to young ones that develop inside the mother (human, cow).

Explain vegetative propagation with two examples and two advantages.3 marks

Vegetative propagation is the growth of a new plant from a vegetative part such as stem, root or leaf. Examples: potato from the "eyes" of a tuber; Bryophyllum from buds on leaf margins. Advantages: plants grow faster and bear fruit earlier; all offspring are identical to the parent, so good traits are kept.

Compare asexual and sexual reproduction (at least four points) and explain why sexual reproduction is important for evolution.5 marks

Asexual: one parent, no gametes, offspring identical to the parent, fast, and common in simple organisms (fission, budding, spore formation). Sexual: two parents, male and female gametes fuse to form a zygote, offspring show variation, slower and needs more energy. Sexual reproduction mixes genes from two parents, producing variation; some variants survive better when the environment changes, so species can adapt and evolve over generations.

Quick revision

Asexual = one parent, no gametes.
Fertilisation forms the zygote.
Potato reproduces through its eyes (buds on the tuber).

Exam tips

Learn one example for every method of asexual reproduction.
Fish and frogs lay many eggs because external fertilisation wastes many.

Practice MCQs

Yeast reproduces mainly by
1. binary fission
2. budding
3. spores
4. fragmentation
Show answer
Answer: (b) budding. Budding.
The fertilised egg is called a
1. zygote
2. gamete
3. embryo
4. spore
Show answer
Answer: (a) zygote. Zygote.
Animals that lay eggs are
1. viviparous
2. parasitic
3. asexual
4. oviparous
Show answer
Answer: (d) oviparous. Oviparous.
Potato is propagated by its
1. tuber (stem)
2. root
3. leaf
4. seed only
Show answer
Answer: (a) tuber (stem). Modified stem with buds.
Frogs show
1. internal fertilisation
2. fragmentation
3. budding
4. external fertilisation
Show answer
Answer: (d) external fertilisation. In water.
Bread mould (Rhizopus) reproduces by
1. budding
2. fission
3. spores
4. layering
Show answer
Answer: (c) spores. Spore formation.
Offspring produced by asexual reproduction are nearly identical because
1. they come from two parents
2. they live together
3. they eat the same food
4. they come from one parent without mixing of genes
Show answer
Answer: (d) they come from one parent without mixing of genes. No fusion of gametes.
Which is a viviparous animal?
1. cow
2. frog
3. hen
4. lizard
Show answer
Answer: (a) cow. Gives birth to young ones.

All chapters of Class 9 Science

Written by Kundali IQ from standard, well-established facts to help with revision. This is not an official NCERT publication; always read your textbook too.