Is it correct to say: Confusing budding in Hydra with budding in Yeast?

Both bud, but Yeast is a unicellular fungus while Hydra is a multicellular animal. Same mechanism at different levels of organisation.

Is it correct to say: Calling fragmentation and regeneration the same?

Fragmentation = pieces break apart and each grows into an adult (Spirogyra). Regeneration = replacing lost parts (Hydra, Planaria) — usually not a full reproductive mode.

Is it correct to say: Saying pollen is the female gamete?

Pollen carries MALE gametes. Female gamete is inside the OVULE.

Is it correct to say: Confusing pollination with fertilisation?

Pollination = transfer of pollen from anther to stigma. Fertilisation = fusion of male gamete with egg inside the ovule.

Is it correct to say: Writing chromosome number of human sperm as 46?

Sperm and egg are HAPLOID (23 chromosomes). Zygote formed after fertilisation is DIPLOID (46).

Is it correct to say: Assuming menstruation happens without ovulation?

Menstruation follows an unfertilised ovulation cycle. Ovulation → no fertilisation → uterine lining shed as menstrual flow.

Formula sheet (PDF) →

Biology · Chapter 7

How do Organisms Reproduce?

Modes of asexual and sexual reproduction, flower structure, human reproductive system, contraception and reproductive health — NCERT Class 10 Science Ch 7

8 formulas · 3 solved examples · 6 practice questions · Board weight: 6 marks · CBSE Class 10 · 2025–26 syllabus

Board Exam Tips

→Labelled diagram of a bisexual flower with function of stamen and carpel — reliable 3-mark answer.
→Difference between fission, budding, fragmentation, regeneration, spore formation and vegetative propagation — 3 marks.
→Human male + female reproductive systems: labelled diagrams appear every year.
→Menstrual cycle timeline (about 28 days) — draw a small chart.
→Contraception methods classified: mechanical, chemical, IUD, surgical — 2-3 marks.

Formulas(8)

Reproduction TypesBoard favourite

Reproduction = Asexual (1 parent, clones) + Sexual (2 parents, variation)

Fission

Parent cell ⟶ 2 (binary) or many (multiple)

Budding

Parent ⟶ parent + bud \to new individual

Vegetative PropagationBoard favourite

Root/Stem/Leaf ⟶ new plant

Sexual Reproduction Steps

Gametogenesis \to Fertilisation \to Zygote \to Embryo \to Development

Pollination and Fertilisation in Flower

Pollen \to stigma \to pollen tube through style \to ovary \to fusion with egg

Menstrual Cycle Length

Cycle \approx 28 days; ovulation on day \approx 14

Human Chromosome Count in GametesBoard favourite

Gamete: n = 23; Zygote: 2 n = 46

Solved Examples

1Solved Exampleeasy4 steps

List any four modes of asexual reproduction with one example each.

Fission — Amoeba (binary), Plasmodium (multiple).

2Solved Exampleboard4 steps

Draw a labelled diagram of a bisexual flower and describe the function of stamens and carpels.

Parts to label: sepals, petals, stamen (anther + filament), carpel (stigma + style + ovary).

3Solved ExampleHOTS4 steps

Explain how contraception methods are classified. Give one example from each class and mention one limitation.

Mechanical / barrier — physically prevent sperm from reaching egg (condom, diaphragm). Also protect against STIs. Failure rate ~2-15%.

Traps & Common Mistakes

Common Mistakes6

1
Confusing budding in Hydra with budding in Yeast
✓Both bud, but Yeast is a unicellular fungus while Hydra is a multicellular animal. Same mechanism at different levels of organisation.
2
Calling fragmentation and regeneration the same
✓Fragmentation = pieces break apart and each grows into an adult (Spirogyra). Regeneration = replacing lost parts (Hydra, Planaria) — usually not a full reproductive mode.
3
Saying pollen is the female gamete
✓Pollen carries MALE gametes. Female gamete is inside the OVULE.
4
Confusing pollination with fertilisation
✓Pollination = transfer of pollen from anther to stigma. Fertilisation = fusion of male gamete with egg inside the ovule.
5
Writing chromosome number of human sperm as 46
✓Sperm and egg are HAPLOID (23 chromosomes). Zygote formed after fertilisation is DIPLOID (46).
6
Assuming menstruation happens without ovulation
✓Menstruation follows an unfertilised ovulation cycle. Ovulation → no fertilisation → uterine lining shed as menstrual flow.

Practice Yourself

Practice Yourself6 questions

Q1
Name one plant that reproduces (a) by leaves, (b) by stems, (c) by roots.
Q2
Give two differences between self and cross pollination.
Q3
State two functions of the placenta.
Q4
What are secondary sexual characters? Give one example each in males and females.
Q5
Name any two sexually transmitted infections (STIs) and one method to prevent them.
Q6
Why is variation important for a species?

Notes

How do Organisms Reproduce?

Reproduction ensures continuity of species and, when sexual, generates variation — the raw material of evolution.

Two big categories

Asexual — one parent; offspring are genetic clones. Fast; useful when conditions are stable.
Sexual — two parents; gamete fusion; offspring have new combinations of genes. Slower but adaptive.

Modes of asexual reproduction

Mode	Example
Binary fission	Amoeba
Multiple fission	Plasmodium
Budding	Yeast, Hydra
Fragmentation	Spirogyra
Regeneration	Planaria
Spore formation	Rhizopus, ferns
Vegetative propagation	Potato, ginger, Bryophyllum

Sexual reproduction — flower

Male part (stamen) = anther + filament. Anther produces pollen.
Female part (carpel) = stigma + style + ovary. Ovary contains ovules.
Pollination: pollen → stigma (self or cross).
Fertilisation: pollen tube delivers male gametes to ovule; double fertilisation gives zygote (2n) + endosperm (3n).
After fertilisation: ovary → fruit; ovule → seed.

Human reproduction — quick anatomy

Male: testes (produce sperm + testosterone) → vas deferens → seminal vesicles + prostate (semen) → urethra.
Female: ovaries (produce eggs + oestrogen/progesterone) → fallopian tube (site of fertilisation) → uterus (implantation) → vagina.
Puberty → menstrual cycle (~28 days) → ovulation on day ~14.

Reproductive health

Contraception: barrier (condom), hormonal (pill), IUD (copper-T), surgical (vasectomy/tubectomy).
STIs: gonorrhoea, syphilis, HIV/AIDS — best prevented by barrier methods.
Prenatal sex determination is illegal in India (PCPNDT Act).