NCERT Solutions for Class 9 Science Chapter 11 – Reproduction: How Life Continues

Introduction

NCERT Solutions for Class 9 Science Chapter 11, Reproduction: How Life Continues, help students understand how living organisms produce new individuals and maintain the continuity of life. This chapter from the new NCERT textbook, Exploration: A Textbook of Science for Grade 9, introduces the importance of reproduction and explores the different ways in which organisms reproduce.

The solutions provide clear explanations for the questions and activities in the textbook. Students can use them to understand important biological concepts, study diagrams and processes, revise key terms, and prepare effectively for examinations.

NCERT Intext Solution

(For question see NCERT)

1. Question

Answer: The next process is fertilisation. The male gamete will travel through the pollen tube and fuse with the female gamete (egg cell) inside the ovule, forming a zygote.

2. Question

Answer: These seeds are adapted for wind dispersal (anemochory).

Reason: They have light, feathery, hair-like structures that help them float and travel long distances with the wind.

3. Question

Answer: This is cross-pollination.

Reason: Pollen is transferred from the flower of one plant variety to the stigma of a flower of another plant variety, leading to seed formation.

4. Question

Answer: Animals with external fertilisation produce more eggs because many eggs and sperms are lost in the environment and do not get fertilised. Also, many fertilised eggs may be eaten by predators or fail to develop. Producing a large number of eggs increases the chances that some offspring will survive.

5. Question

Answer: Internal fertilisation provides greater protection to the gametes because fertilisation occurs inside the female’s body, where the gametes are protected from environmental hazards, drying out, and predators.

Therefore, gametes are more protected in internal fertilisation than in external fertilisation.

6. Question

Answer: Ravi is entering adolescence (puberty). These are common physical changes that occur during adolescence due to hormonal changes.

7. Question

Answer: If Rina’s menstrual cycle is 28 days, her next period is expected 28 days after 5th March.

5 March + 28 days = 2 April

Next period is most likely on 2 April.

8. Question

Answer: A human zygote has 46 chromosomes (23 pairs).

Reason:

• Sperm contributes 23 chromosomes.
• Egg contributes 23 chromosomes.
• After fertilisation, the zygote has 46 chromosomes.

Answer: 46 chromosomes.

9. Question

Answer: Condoms (male or female condoms) are protective devices that help reduce the spread of sexually transmitted infections (STIs) by preventing direct contact and exchange of body fluids.

10. Question

Answer:
Oral contraceptive pills help prevent pregnancy but do not protect against sexually transmitted infections (STIs). Therefore, the risk of infections such as HIV/AIDS, gonorrhoea, and syphilis remains because these diseases can spread through sexual contact and body fluids. Condoms are needed to reduce the risk of STIs.

Short Answer (Exam Style):

1. Condoms are used to reduce the spread of STIs.
2. Risk remaining: STIs can still spread because oral contraceptive pills prevent pregnancy but do not protect against infections.

11. Question

Answer: Human babies remain dependent on their parents for a long period, which has both advantages and disadvantages.

Advantages:

• Parents can provide protection and care during the early years.
• Children have more time to learn language, social skills, and complex behaviours.
• Long parental care helps in better brain development and increases chances of survival.

Disadvantages:

• Human infants require continuous care and support for many years.
• Parents need to invest considerable time, energy, and resources in raising children.
• The prolonged dependency limits the number of offspring that can be raised at one time.

In brief (Exam Point):
Long-term dependence of human babies allows better learning and development but requires extended parental care and greater investment of resources.

NCERT Exercise Solution

(For question see NCERT)

1. Question

Answer: (ii) Cross-pollination

2. Question

Answer: (iii) → (i) → (ii) → (iv)
Pollination → Pollen germination on stigma → Fertilisation → Formation of zygote

3. Assertion–Reason

Assertion (A): The zygote formed after fertilisation immediately attaches to the uterus wall.
Reason (R): The uterus wall is always prepared to receive the zygote.

Answer: (iv) A is false, but R is true.

Explanation: The zygote does not attach immediately. It first divides to form an embryo and then implants in the uterus after a few days.

4. Question

Answer:
Asexual reproduction involves only one parent and no fusion of gametes. Offspring are produced by mitotic cell division, so they receive the same genetic material as the parent and are genetically identical (clones).

5. Question

Answer:
During pregnancy, hormones maintain the uterine lining for the developing embryo. Since the lining is not shed, menstruation stops until after childbirth.

6. Question

Answer:
White or light-coloured flowers are more visible in dim light at night. This helps attract night pollinators such as moths and bats.

7. Question

Answer:
Vegetatively propagated plants are genetically identical. If one plant is susceptible to a disease, all similar plants are likely to be affected. Sexually reproduced plants show genetic variation, increasing the chance that some individuals resist diseases.

8. Question

Answer:
Genetic diversity would gradually decrease because self-pollination mixes genes from the same plant repeatedly. Reduced diversity makes the population less adaptable to environmental changes and diseases.

9. Question

Answer:
The farmer can use vegetative propagation (cutting, layering, grafting) or tissue culture.

Why effective?

• Produce large numbers of plants quickly.
• Offspring are genetically identical to the parent.
• Desired traits are preserved.
• Tissue culture can produce thousands of plants in a short time under controlled conditions.

10. Question

(i) What are the different hypotheses which can be tested using this set-up?

1. Sugar concentration affects pollen germination.
2. Pollen grains will not germinate or germinate poorly in the absence of sugar.
3. There is an optimum sugar concentration at which maximum pollen germination occurs.
4. Very high sugar concentrations may reduce pollen germination.

(ii) What parameters should be kept the same in this set-up?

• Type and age of pollen grains
• Number of pollen grains on each slide
• Volume of sugar solution
• Temperature
• Light conditions
• Time allowed for germination
• Size and type of slide

11. Question

12. Question

(i) What are the hypotheses of the investigation?

1. Bee colonies increase pollination in apple orchards.
2. Better pollination increases fruit setting.
3. Better pollination decreases fruit drop.
4. Orchards with managed bee colonies will produce higher yields than those relying only on natural pollinators.

(ii) What are the different parameters in the experiment?

Independent Variable:

• Presence or absence of managed bee colonies.

Dependent Variables:

• Fruit setting (%)
• Fruit drop (%)
• Apple yield

Controlled Variables:

• Variety of apple trees
• Climate and soil conditions (as far as possible)
• Irrigation and fertilizer application
• Age of trees

(iii) Compare Places A and B in terms of apple yield.

• Place A (Natural pollination):
  • Lower fruit setting
  • Higher fruit drop
  • Lower overall yield
• Place B (With bee colonies):
  • Higher fruit setting
  • Lower fruit drop
  • Higher overall yield

Thus, Place B produced more apples than Place A.

(iv) What do you infer from the data?

The presence of managed bee colonies improves pollination efficiency, increases fruit setting, reduces fruit drop, and significantly enhances apple yield. Therefore, beekeeping can help overcome the decline in natural pollinators and improve apple production.

13. Question

Answer: The claim is not always correct.

Reasons:

1. Not all women have a 28-day menstrual cycle; cycle length can vary from person to person.
2. Ovulation generally occurs about 14 days before the next menstrual period, not necessarily on the 14th day of the cycle.
3. Stress, illness, hormonal changes, diet, and lifestyle can alter the timing of ovulation.
4. Some cycles may have early, late, or even no ovulation.

Conclusion: Ovulation often occurs around day 14 in a 28-day cycle, but it does not always occur on day 14 in every menstrual cycle.

Class 9 Science Chapter 11 – Reproduction: How Life Continues

This chapter explores reproduction as an essential life process through which organisms produce new individuals and ensure the continuity of their species.

Students learn about the different modes of reproduction and how reproductive processes differ among organisms. The chapter also helps students understand how reproduction contributes to continuity as well as variation in living organisms.

Use this section to explain the specific reproductive processes, examples, structures, and diagrams covered in the current NCERT Chapter 11.

Common Mistakes to Avoid in Chapter 11

Students should avoid:

• Confusing reproduction with growth.
• Mixing up different modes of reproduction.
• Confusing reproductive structures and their functions.
• Missing steps when explaining a biological process.
• Incorrectly labelling diagrams.
• Confusing fertilisation with other stages of reproduction.
• Memorising processes without understanding their sequence.
• Giving examples that do not match the reproductive method being described.

FAQs

What is Chapter 11 of Class 9 Science?

Chapter 11 of the new Class 9 Science textbook is Reproduction: How Life Continues. It introduces reproduction as an important life process and explores the reproductive methods and concepts covered in the chapter.

Why is reproduction important?

Reproduction enables living organisms to produce new individuals and helps maintain the continuity of a species.

What are the main modes of reproduction?

The major modes discussed in school-level biology include asexual and sexual reproduction. The specific processes and examples should be studied from the current NCERT chapter.

What is asexual reproduction?

Asexual reproduction is a mode of reproduction that does not involve the fusion of reproductive cells from two parents. The exact forms and examples covered should be learned from the textbook.

What is sexual reproduction?

Sexual reproduction involves reproductive cells and their processes of formation and fusion, as described in the chapter. It can contribute to variation among offspring.

What are the important topics in Chapter 11?

Important topics include the importance of reproduction, modes of reproduction, reproductive processes, reproductive structures, and the concepts and examples covered in the current textbook.

How should I prepare Class 9 Science Chapter 11?

Read the NCERT chapter carefully, understand the reproductive processes and diagrams, practise the textbook questions and activities, and revise important terms. Use NCERT Solutions to check your answers.

Are NCERT Solutions enough to study Chapter 11?

NCERT Solutions are useful for understanding textbook questions, but students should also read the complete chapter and practise diagrams, processes, activities, and questions independently.

Is Chapter 11 important for the Class 9 Science exam?

Yes. Students should understand the reproductive processes, terminology, diagrams, and concepts included in the chapter rather than relying only on memorisation.