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How do Organisms Reproduce? – Class 10 Science notes, important questions and MCQs

NCERT Class 10 Science, chapter 7. Notes, key terms, important questions with answers and MCQs.

Chapter overview

Reproduction produces new individuals and passes DNA to them. It can be asexual (one parent, copies) or sexual (two parents, variation).

Asexual reproduction

Fission (Amoeba binary, Plasmodium multiple), fragmentation (Spirogyra), regeneration (Planaria), budding (Hydra, yeast).
Vegetative propagation: new plants from stem, root or leaf (Bryophyllum leaves, potato tubers); grafting and layering.
Spore formation (Rhizopus).

Sexual reproduction in flowering plants

Stamen (anther, filament) is male; pistil (stigma, style, ovary) is female.
Pollination: transfer of pollen to the stigma (self or cross).
Fertilisation forms a zygote; the ovule becomes the seed and the ovary becomes the fruit.

Human reproduction and health

Male: testes make sperm and testosterone. Female: ovaries release eggs; fertilisation in the fallopian tube; the embryo implants in the uterus and gets nourishment through the placenta.
Puberty brings changes due to hormones.
Contraception methods (barrier, hormonal, surgical) prevent pregnancy; barrier methods also protect against STDs.

Key terms

Binary fission: one cell splits into two equal cells
Pollination: transfer of pollen from anther to stigma
Zygote: the cell formed after fertilisation
Placenta: tissue joining the embryo to the mother's uterus for nutrition

Formulas

DNA copying with small changes produces variation

Important questions with answers

Why is variation useful for a species?2 marks

Variation helps some individuals survive when the environment changes (for example, heat-resistant bacteria in a heat wave), so the species does not get wiped out.

Distinguish between binary fission and multiple fission with examples.3 marks

In binary fission a parent cell splits into two daughter cells (Amoeba, Leishmania). In multiple fission the nucleus divides many times inside a cyst and many daughter cells are released at once (Plasmodium).

Describe the sexual reproduction events in a flower: pollination, fertilisation and the changes after fertilisation.5 marks

Pollination is the transfer of pollen from the anther to the stigma, by self- or cross-pollination through wind, water or animals. A pollen tube grows from the stigma through the style to the ovule and carries the male germ cell, which fuses with the female germ cell (egg) to form a zygote. After fertilisation, the zygote forms the embryo, the ovule becomes the seed, the ovary becomes the fruit, and the petals, sepals and stamens usually fall off.

Quick revision

Asexual = one parent; sexual = two parents and variation.
Fertilisation in humans happens in the fallopian tube.
Placenta supplies food and oxygen to the embryo.

Exam tips

Write example + organism pairs: budding–Hydra, regeneration–Planaria, spores–Rhizopus.
In plants, after fertilisation: ovule → seed, ovary → fruit.

Practice MCQs

Hydra reproduces by
1. budding
2. fission
3. spores
4. fragmentation
Show answer
Answer: (a) budding. Budding.
The male part of a flower is the
1. stamen
2. pistil
3. ovary
4. sepal
Show answer
Answer: (a) stamen. Stamen.
Amoeba reproduces by
1. binary fission
2. budding
3. spores
4. layering
Show answer
Answer: (a) binary fission. Binary fission.
After fertilisation, the ovary develops into the
1. seed
2. fruit
3. flower
4. leaf
Show answer
Answer: (b) fruit. Ovary → fruit.
Bryophyllum is propagated by
1. roots
2. spores
3. seeds only
4. leaves
Show answer
Answer: (d) leaves. Buds on leaf margins.
In humans, fertilisation normally takes place in the
1. uterus
2. ovary
3. vagina
4. fallopian tube
Show answer
Answer: (d) fallopian tube. Oviduct.
Which method of contraception also protects against sexually transmitted diseases?
1. copper-T
2. oral pills
3. surgery
4. condom
Show answer
Answer: (d) condom. Barrier method.
Why does sexual reproduction help a species survive?
1. it is faster
2. it avoids DNA copying
3. it needs one parent
4. it creates variation
Show answer
Answer: (d) it creates variation. Variation helps adaptation.

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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.