NCERT Class 9 Science Reproduction How Life Continues Solutions
Short Intro
This chapter explains how living organisms reproduce and ensure continuity of life. Students learn about asexual and sexual reproduction in plants and animals, pollination, fertilisation, reproductive systems in humans, menstruation, pregnancy, and methods of birth control with detailed explanations and solved questions.
Quick Information Box
| Topic | Details |
|---|---|
| Chapter Name | Reproduction: How Life Continues |
| Class | Grade 9 |
| Subject | Science |
| Main Topics | Reproduction in Plants and Humans |
| Important Processes | Pollination, Fertilisation, Meiosis |
| Human Chromosomes | 46 |
| Gametes Chromosomes | 23 |
Concepts Used (Topics Covered)
- Asexual Reproduction
- Budding and Spore Formation
- Sexual Reproduction
- Meiosis and Gamete Formation
- Pollination and Fertilisation
- Self and Cross Pollination
- Flower Structure
- Reproduction in Animals
- Human Male Reproductive System
- Human Female Reproductive System
- Menstrual Cycle
- Pregnancy and Childbirth
- Contraceptive Methods
- Sexually Transmitted Infections (STIs)
Important Formulas
- Number of Chromosomes in Human Gametes
= 23 - Number of Chromosomes in Human Body Cells
= 46 - Fertilisation
Male Gamete + Female Gamete → Zygote - Menstrual Cycle Duration
≈ 28 days - Ovulation
Occurs approximately on Day 14
Questions & Step-by-step Solutions with Explanation
Q1. Artificial Pollination Experiment
Question:
A flower’s anthers are removed before maturity and pollen from another plant is dusted onto stigma. Which process is ensured?
Solution:
Pollen is transferred from one plant to another plant of same species.
Answer:
Cross-pollination
Q2. Correct Sequence in Plant Reproduction
Given:
(i) Pollen germination on stigma
(ii) Fertilisation
(iii) Pollination
(iv) Formation of zygote
Solution:
First pollination occurs, then pollen germinates, fertilisation takes place, and finally zygote forms.
Correct Order:
(iii) → (i) → (ii) → (iv)
Q3. Assertion and Reason
Assertion:
The zygote formed after fertilisation immediately attaches to uterus wall.
Reason:
The uterus wall is always prepared to receive zygote.
Solution:
Zygote first divides repeatedly before implantation.
Uterus lining changes cyclically and is not always ready.
Answer:
(iv) A is false but R is true.
Q4. Why Asexual Reproduction Produces Identical Offspring
Solution:
Asexual reproduction involves only mitosis.
No fusion of gametes occurs.
Therefore offspring receive identical genetic material from parent.
Answer:
Offspring are genetically identical because only mitotic division occurs.
Q5. Why Menstruation Stops During Pregnancy
Solution:
During pregnancy, uterus lining is needed to nourish embryo.
Therefore uterine lining is not shed.
Answer:
Menstruation stops because the uterus retains its thick lining for embryo development.
Q6. Why Night Blooming Flowers are White
Solution:
White or light coloured flowers are easily visible at night.
This helps attract pollinators like moths and insects.
Answer:
Night flowers are light coloured to attract pollinators in darkness.
Q7. Why Vegetatively Propagated Plants are Vulnerable
Solution:
Vegetative propagation produces clones with little variation.
If disease affects one plant, all similar plants may be affected.
Answer:
Lack of genetic variation makes them more vulnerable to diseases.
Q8. Effect of Only Self-pollination
Solution:
Self-pollination reduces genetic variation.
Over generations, adaptability decreases.
Answer:
Genetic diversity decreases due to lack of mixing of genes.
Q9. Method for Producing Identical Plants Quickly
Solution:
Vegetative propagation or tissue culture can be used.
These methods produce clones rapidly.
Answer:
Vegetative propagation is suitable for producing identical plants quickly.
Q10. Pollen Germination Experiment
(i) Possible Hypotheses
- Sugar concentration affects pollen germination.
- Optimum sugar concentration gives maximum germination.
(ii) Parameters to Keep Constant
- Temperature
- Type of pollen
- Time duration
- Slide conditions
- Quantity of solution
Q11. Type of Pollination
Tomato:
Self-pollination because stamens cover stigma.
Wheat:
Wind pollination
Papaya:
Cross-pollination because male and female flowers are on different plants.
Q12. Apple Orchard Investigation
(i) Hypothesis
Bee pollination increases fruit yield.
(ii) Parameters
- Presence of bees
- Fruit setting
- Fruit drop
- Number of flowers
(iii) Data Analysis
Place B with beekeeping shows:
- Higher fruit setting
- Lower fruit drop
(iv) Inference
Pollinators increase successful pollination and crop yield.
Q13. Ovulation Claim
Statement:
“Ovulation always occurs on day 14.”
Solution:
This is not always correct.
Reasons:
- Menstrual cycles vary among females.
- Stress, illness, and hormones affect ovulation timing.
Answer:
The statement is incorrect.
Q14. Why External Fertilisation Produces Many Eggs
Solution:
Many eggs are destroyed or eaten in water.
Producing large numbers increases survival chances.
Answer:
External fertilisation requires many eggs due to low survival rate.
Q15. Which Fertilisation Gives More Protection
Solution:
Internal fertilisation protects gametes and embryo inside body.
Answer:
Internal fertilisation provides more protection.
Q16. Function of Flower Parts
| Flower Part | Function |
|---|---|
| Sepal | Protects bud |
| Petal | Attracts pollinators |
| Stamen | Produces pollen |
| Pistil | Female reproductive part |
Q17. Why Pollination is Necessary
Solution:
Pollination transfers pollen grains to stigma.
This enables fertilisation and seed formation.
Answer:
Pollination is essential for fruit and seed formation.
Q18. Human Male Reproductive System
Main Parts:
- Testes
- Scrotum
- Vas deferens
- Urethra
- Penis
Function:
Production and transfer of sperm.
Q19. Human Female Reproductive System
Main Parts:
- Ovary
- Oviduct
- Uterus
- Cervix
- Vagina
Function:
Production of eggs and development of foetus.
Q20. What Happens During Fertilisation
Solution:
Sperm fuses with egg in oviduct.
A zygote is formed.
Answer:
Fusion of male and female gametes forms zygote.
Q21. Menstrual Cycle Stages
| Days | Process |
|---|---|
| 1–5 | Menstruation |
| 6–14 | Uterus lining rebuilds |
| 14 | Ovulation |
| 15–28 | Thickening of uterus lining |
Q22. Why Condoms are Important
Solution:
Condoms prevent:
- Pregnancy
- Sexually transmitted infections
Answer:
Condoms act as protective barrier methods.
Q23. Difference Between Sperm and Egg
| Feature | Sperm | Egg |
|---|---|---|
| Size | Small | Large |
| Number | Millions | Few |
| Movement | Motile | Non-motile |
Q24. IVF Technique
Solution:
Fertilisation occurs outside body in laboratory dish.
Embryo is implanted into uterus.
Answer:
IVF helps couples facing fertility problems.
Common Mistakes
- Confusing pollination with fertilisation
- Mixing self-pollination and cross-pollination
- Forgetting functions of flower parts
- Confusing mitosis and meiosis
- Incorrect understanding of menstruation cycle
Exam Tips
- Draw labelled diagrams of flower and reproductive systems.
- Learn definitions carefully.
- Revise menstrual cycle stages regularly.
- Remember differences between sperm and egg.
- Practice assertion-reason questions.
Practice MCQs
1. Transfer of pollen to stigma is called:
A. Fertilisation
B. Pollination
C. Germination
D. Budding
Answer:
B. Pollination
2. Male reproductive part of flower:
A. Pistil
B. Ovary
C. Stamen
D. Ovule
Answer:
C. Stamen
3. Human gametes contain:
A. 46 chromosomes
B. 23 chromosomes
C. 92 chromosomes
D. 12 chromosomes
Answer:
B. 23 chromosomes
4. Fertilisation in frogs is generally:
A. Internal
B. External
C. Artificial
D. Vegetative
Answer:
B. External
5. Which method prevents STIs?
A. Copper-T
B. Oral pills
C. Condoms
D. Surgery
Answer:
C. Condoms
FAQ Section
Q1. What is reproduction?
It is the biological process through which organisms produce new individuals.
Q2. What is pollination?
Transfer of pollen grains from anther to stigma.
Q3. What is fertilisation?
Fusion of male and female gametes.
Q4. Why is meiosis important?
It reduces chromosome number to half in gametes.
Q5. What is menstruation?
Monthly shedding of uterine lining when fertilisation does not occur.
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