🌱 Class 9 Science – Reproduction: How Life Continues Original Visual Revision Notes
Aligned with the Class 9 Science syllabus. Independently created study material. Not affiliated with or endorsed by NCERT.
💡 Think about this first! Every single person alive today exists because of one remarkable chain — your parents, their parents, their parents, going all the way back millions of years without a single break! This unbroken chain is possible only because of reproduction. Some living things copy themselves all alone (like a broken piece of starfish that grows into a whole new starfish!), while others need a partner. In this lesson, we discover all the clever ways life keeps itself going — from tiny yeast cells to flowering plants to human babies.
🌱 Topic 1: What is Reproduction
Reproduction means making new living beings.
All living things reproduce to continue their kind.
Parents produce offspring that look like them.
Without reproduction, species would disappear forever.
There are two main types of reproduction.
🔀 Topic 2: Asexual vs Sexual
Asexual means only one parent is needed.
Offspring are exact copies of the single parent.
Sexual means two parents are needed together.
Sexual offspring get traits from both parents.
Sexual reproduction creates variation in offspring.
🌿 Topic 3: Vegetative Propagation
New plants grow from stems, roots, or leaves.
A cutting is a stem piece planted in soil.
Rose plants grow easily from stem cuttings.
Layering means bending a stem into the ground.
Grafting joins two different plant parts together.
🦠 Topic 4: Budding and Spore Formation
In budding, a small bud grows on parent.
The bud gets bigger and then separates out.
Yeast and hydra reproduce by making buds.
Spores are tiny cells that grow into new organisms.
Bread mould spreads by releasing many tiny spores.
🔬 Topic 5: Meiosis and Gametes
Gametes are special cells for sexual reproduction.
Male gamete is called a sperm cell.
Female gamete is called an egg cell.
Meiosis is cell division that halves chromosome number.
Human body cells have 46, gametes have 23.
🌼 Topic 6: Parts of a Flower
Sepals are green covers that protect the bud.
Petals are colourful parts that attract insects.
Stamen is the male part that makes pollen.
Pistil is the female part with ovary inside.
A bisexual flower has both stamen and pistil.
🐝 Topic 7: Pollination Types
Pollination is transfer of pollen to the pistil.
Self-pollination happens inside the same flower.
Cross-pollination moves pollen between two flowers.
Wind, water, and insects help carry the pollen.
Bees and butterflies are common pollinators.
🌱 Topic 8: Fertilisation and Seed Formation
Pollen tube grows down into the ovule.
Male cell joins with egg cell inside ovule.
This joining is called fertilisation.
After fertilisation, ovule becomes a seed.
The ovary grows bigger and becomes a fruit.
🧑 Topic 9: Human Reproductive System
Males have testes that produce sperm cells.
Females have ovaries that produce egg cells.
The uterus is where the baby grows safely.
Sperm joins egg inside the fallopian tube.
The fertilised egg attaches to the uterus wall.
🌟 Topic 10: Puberty and Menstrual Cycle
Puberty is when the body becomes able to reproduce.
It usually starts between ages 10 and 14.
Hormones cause body changes during this time.
The menstrual cycle repeats about every 28 days.
If no baby forms, the uterus lining sheds.
🎨 Section 2 — Easy Illustrations
Fig 1: Budding in hydra — from parent to new organism in three stages
Fig 2: Parts of a flower with labels
Fig 3: Self pollination stays in one flower, cross pollination needs two flowers
Fig 4: From pollination to seed formation in four steps
Fig 5: Oviparous animals lay eggs, viviparous animals give birth to live young
🔬 Section 3 — Worked Examples
💡 Example 1: Chromosome Numbers after Meiosis
A plant body cell has 32 chromosomes. How many chromosomes will its gamete have?
1
Body cell chromosome count = 32.
2
Meiosis divides the chromosome number by 2.
3
Gamete chromosomes = 32 ÷ 2 = 16.
Gamete = Body cell chromosomes ÷ 2
Answer: Each gamete will have 16 chromosomes.
💡 Example 2: Zygote Chromosome Count
A male frog gamete has 13 chromosomes. A female frog gamete also has 13 chromosomes. How many chromosomes will the baby frog have?
1
Male gamete (sperm) = 13 chromosomes.
2
Female gamete (egg) = 13 chromosomes.
3
Zygote = sperm + egg = 13 + 13 = 26.
Zygote = Male gamete + Female gamete
Answer: The baby frog will have 26 chromosomes.
💡 Example 3: Menstrual Cycle Timing
A girl’s menstrual period started on the 3rd of a month. Her cycle length is 28 days. When will her next period start?
1
Current period started = Day 3 of month.
2
Cycle length = 28 days.
3
Next period = 3 + 28 = Day 31 of same month (or Day 1 of next month if month has 30 days).
Next period = Start date + Cycle length
Answer: The next period starts on the 31st day (about 4 weeks later).
📋 Section 4 — Cheat Sheet
Term
Meaning
Reproduction
Process of making new living organisms.
Asexual Reproduction
One parent makes offspring on its own.
Sexual Reproduction
Two parents combine gametes for offspring.
Vegetative Propagation
New plant grows from stem, root, or leaf.
Budding
A bud grows on parent and separates out.
Spore Formation
Tiny cells spread to form new organisms.
Gamete
A sex cell (sperm in males, egg in females).
Meiosis
Cell division that halves chromosome number.
Pollination
Transfer of pollen from stamen to stigma.
Fertilisation
Male cell joins female cell to form zygote.
Zygote
Cell formed when sperm and egg join together.
Pistil
Female part of flower: stigma, style, ovary.
Stamen
Male part of flower: anther and filament.
Oviparous
Animals that lay eggs (birds, reptiles).
Viviparous
Animals that give birth to live young.
Puberty
Age when the body can reproduce (10–14 years).
Menstrual Cycle
Monthly cycle of uterus lining (about 28 days).
🏠 Section 5 — Take-Home Handout
Part A: Fill in the Blanks
1. Reproduction means making new _______ beings.
2. In asexual reproduction, only _______ parent is needed.
3. Hydra reproduces by growing a small _______.
4. The female part of a flower is called the _______.
5. Meiosis reduces the chromosome number by _______.
Part B: True or False
1. Sexual reproduction needs two parents. _______
2. Spores are very large cells that we can see easily. _______
3. Cross pollination moves pollen to a different flower. _______
4. After fertilisation, the ovary becomes a seed. _______
5. Human gametes have 23 chromosomes each. _______
Part C: Solve These
1. A cat body cell has 38 chromosomes. How many chromosomes will its egg cell have?
2. A dog sperm has 39 chromosomes. A dog egg also has 39 chromosomes. How many chromosomes will the puppy have?
3. A girl’s period started on the 5th of June. Her cycle is 28 days. When will the next period start?
Part D: Match the Columns
Column A
Column B
Your Answer
1. Budding
A. Transfer of pollen to stigma
2. Pollination
B. Sperm joins with egg cell
3. Fertilisation
C. Baby grows inside mother
4. Viviparous
D. Yeast and hydra do this
5. Meiosis
E. Halves the chromosome number
Part E: Draw and Label
Draw a simple flower. Label: Sepal, Petal, Stamen (male), and Pistil (female).
In asexual reproduction, only one parent is needed.
Hydra reproduces by growing a small bud.
The female part of a flower is called the pistil (carpel).
Meiosis reduces the chromosome number by half.
Part B: True or False — Answers
True. Sexual reproduction requires two parents — a male and a female — to produce offspring.
False. Spores are tiny, microscopic cells, far too small to see with the naked eye.
True. Cross pollination transfers pollen from the stamen of one flower to the pistil of a different flower.
False. After fertilisation, the ovary becomes a fruit and the ovule inside becomes the seed. The ovary does not become the seed itself.
True. Meiosis halves the chromosome number, so each human gamete (egg or sperm) has 23 chromosomes.
Part C: Solve These — Step-by-Step Solutions
Q1. A cat body cell has 38 chromosomes. How many chromosomes will its egg cell have?
1
Egg cells are made by meiosis, which halves the chromosome number.
2
Egg cell chromosomes = 38 ÷ 2 = 19 chromosomes.
Answer: The cat’s egg cell will have 19 chromosomes.
Q2. A dog sperm has 39 chromosomes. A dog egg also has 39 chromosomes. How many chromosomes will the puppy have?
1
At fertilisation, sperm chromosomes combine with egg chromosomes.
2
Puppy’s chromosomes = 39 + 39 = 78 chromosomes.
Answer: The puppy will have 78 chromosomes in its body cells.
Q3. A girl’s period started on the 5th of June. Her cycle is 28 days. When will the next period start?
1
Add 28 days to 5 June.
2
June has 30 days, so 30 − 5 = 25 days remain in June. 28 − 25 = 3 extra days go into July.
3
Next period = 3 July.
Answer: The next period will start on 3 July.
Part D: Match the Columns — Answers
Column A
Match
Column B
1. Budding
→ D
Yeast and hydra do this
2. Pollination
→ A
Transfer of pollen to stigma
3. Fertilisation
→ B
Sperm joins with egg cell
4. Viviparous
→ C
Baby grows inside mother
5. Meiosis
→ E
Halves the chromosome number
🔄 Section 6 — Revision Flashcards
Light side = Question. Dark side = Answer.
What is reproduction?
Making new living beings from parents.
How many parents does asexual reproduction need?
Only one parent is needed.
What is vegetative propagation?
New plant from stem, root, or leaf.
What does meiosis do?
It halves the chromosome number.
Name the four parts of a flower.
Sepal, petal, stamen, and pistil.
What is fertilisation?
Sperm cell joins with egg cell.
What are oviparous animals?
Animals that lay eggs outside the body.
How long is the human menstrual cycle?
About 28 days from start to start.
🧠 Section 7 — Mind Map
Fig 6: Mind map of reproduction and its key topics
⚠ This is independently created study material aligned with the Class 9 Science syllabus. Not affiliated with or endorsed by NCERT or any government body.