NCERT Solutions for Class 9 Science Chapter 11 Reproduction: How Life Continues - Download PDF

The downloadable PDF of the updated NCERT questions with detailed answers is given below for better learning. Reproduction: How Life Continues Class 9 questions and answers PDF include various topics that form the base of reproductive biology. The NCERT Solutions for Class 9 improve performance and boost confidence for exams.

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Class 9 Science Reproduction Chapter 11 - Revise, Reflect, Refine Exercise Questions With Solutions

All the answers and detailed solutions to the Revise, Reflect, Refine Exercise Questions given at the end of the chapter are given below. The Reproduction: How Life Continues class 9 question-answers form the base of many topics in science for higher classes.

Revise, Reflect, Refine

Question 1: A flower’s anthers are removed before it matures. Later, pollen from another plant of the same species is dusted onto its stigma and seeds are produced. Which process has been ensured here?

(i) Self-pollination

(ii) Cross-pollination

(iii) Fertilisation

(iv) Tissue culture

Answer: Correct option (ii) Cross-pollination

The anthers were removed before maturity, so self-pollination could not occur. Later, pollen from another plant of the same species was placed on the stigma. This led to cross-fertilisation and seed formation.

Question 2: Arrange the following stages of sexual reproduction in plants in the correct order:

(i) Pollen germination on stigma

(ii) Fertilisation

(iii) Pollination

(iv) Formation of zygote

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

The correct order of stages in sexual reproduction in plants is:

1. Pollination - transfer of pollen grains to the stigma.

2. Pollen germination on the stigma - pollen tube formation begins.

3. Fertilisation - fusion of male and female gametes.

4. Formation of zygote - the fertilised egg develops into a zygote.

Question 3: 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.

(i) Both A and R are true, and R is the correct explanation of A.

(ii) Both A and R are true, but R is not the correct explanation of A.

(iii) A is true, but R is false.

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

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

• The statement that the zygote formed after fertilisation immediately attaches to the uterus wall is false. The zygote first undergoes cell divisions and forms a blastocyst before implantation.

• The statement uterus wall is always prepared to receive the zygote is true. The endometrium thickens every cycle under the influence of hormones to support implantation.

Question 4: Why does asexual reproduction produce offsprings that are genetically identical to the parent?

Answer: Asexual reproduction produces offspring that are genetically identical to the parent because it involves only mitotic cell division.

• There is no fusion of gametes, so no mixing of genetic material happens.

• The new individuals inherit the exact DNA of the parent.

• They are clones of the parent with no genetic variation.

Question 5: Explain why the menstrual cycle stops during pregnancy.

Answer: The menstrual cycle stops during pregnancy because the uterine lining is maintained to support the developing baby.

• Every month, the uterus lining becomes thick to prepare for pregnancy.

• After fertilisation, the zygote travels to the uterus and attaches to the lining.

• This implantation marks the beginning of pregnancy.

• During pregnancy, the lining protects and nourishes the baby.

• Menstruation happens only when the lining is not needed.

• Since the lining supports the baby, it is not shed.

Therefore, the menstrual cycle stops during pregnancy.

Question 6: Why are flowers that bloom at night white or light in colour as compared to flowers that bloom during the day?

Answer: Flowers that bloom at night are usually white or light in colour to be easily visible in darkness.

• Bright colours cannot be seen well at night.

• White or pale shades reflect moonlight and stand out clearly.

• This helps nocturnal pollinators like moths and bats locate them easily.

• Many of these flowers also produce a strong fragrance to attract pollinators when visual signals are weak.

Question 7: Why do vegetatively propagated plants tend to be more vulnerable to diseases than sexually reproduced plants?

Answer: Vegetatively propagated plants tend to be more vulnerable to diseases than sexually reproduced plants due to the following reasons:

• Vegetative propagation is a type of asexual reproduction.

• It produces offspring that are genetically identical to the parent.

• There is no mixing of genetic material from two parents.

• Lack of variation makes all plants clones with the same strengths and weaknesses.

• If a disease affects the parent plant, it can easily infect all the offspring.

• In sexual reproduction, variation helps some plants resist diseases.

Vegetatively propagated plants are more vulnerable because they are clones without genetic variation, while sexually reproduced plants have diversity that provides resistance.

Question 8: If all flowers in a type of plant were only capable of self-pollination, how would it affect the genetic diversity over several generations? Explain.

Answer: If all flowers in a type of plant were only capable of self-pollination, it would lead to a significant reduction in genetic diversity over several generations.

• If all flowers only self‑pollinate, there is no mixing of genes from two parents.

• Offspring inherit genetic material from the same plant again and again.

• Over generations, this reduces genetic diversity in the population.

• Lack of variation makes plants less able to adapt to new diseases or environmental changes.

• Self‑pollination provides survival but does not provide the evolutionary advantage of cross‑pollination.

Question 9: A farmer wants to produce a large number of genetically identical plants quickly. Suggest suitable reproduction methods and explain why they are effective.

Answer: To produce a large number of genetically identical plants quickly, a farmer should use vegetative propagation and modern culture methods, which are a form of asexual reproduction.

Here are the specific methods and why they are effective:

Both methods are effective because they involve one parent. It reproduces genetically identical plants and allows rapid, larges-cale farming.

Question 10: Suresh prepares slides with pollen grains in different sugar concentrations (0%, 2.5%, 5%, 7.5%, 10%) to study the germination of pollen.

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

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

Answer:

(i) Hypotheses to be Tested

• Different sugar concentrations affect the percentage of pollen grains that germinate.

• There is a specific sugar level at which maximum pollen tube growth occurs.

• Pollen grains need sugar for germination; in pure water (0%), germination will be very low or absent.

• The rate of pollen tube emergence varies with sugar availability.

(ii) Parameters to Keep the Same

• Maintain constant warm conditions (25-35 °C).

• Use pollen from the same plant species.

• Keep equal time intervals for viewing under the microscope.

• Add the same amount of sugar solution to each slide.

• Provide uniform light and humidity across all slides.

Question 11: Look at the picture given below and think in line with the given prompts and find out which type(s) of pollination might have been followed in these flowers —

Answer:

Tomato - Self-pollination as pollen easily falls on the stigma of the same flower.

Wheat - Self-pollination as pollination occurs before the flower opens, securing fertilisation within the same flower.

Papaya - Cross-pollination occurs when pollen from male flowers on one tree is transferred to female flowers on another tree to get fertilised.

Question 12: In the lower Himalayan region of northern India, apples are an important cash crop that contributes significantly to farmers’ livelihoods. The fruit yield in apple cultivation is declining continuously, associated with climate change and a significant decline in the population of natural pollinators. A researcher-farmer group set up two experimental apple orchards at two distinct locations: Places A and B. In apple orchards at Place A, they allowed natural pollinators Per cent to pollinate the flowers of the apple. In apple orchards at Place B, they applied mixed farming techniques of beekeeping. Along with honey, the farmer yielded apples. The yield of apples is depicted in Fig., in terms of fruit setting (number of fruits/the total number of corresponding fruit-bearing branches) and fruit drop (premature falling of developing fruits) in the two types of experimental places of apple orchards.

(i) What are the hypotheses the researcher-farmers group has thought of for this investigation?

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

(iii) Compare and analyse the data of two experimental orchards, Places A and B, in terms of high yields of apple fruits.

(iv) Based on your analysis, what do you infer from the data?

Answer:

(i) Hypotheses for the Investigation

• Managed pollination (beekeeping) increases fruit set in apple orchards compared to relying only on declining natural pollinator populations.

• The presence of a stable pollinator population through beekeeping will reduce the percentage of premature fruit drop.

• Mixed farming techniques (apples + beekeeping) can provide a sustainable solution to declining crop yields caused by climate change.

(ii) Parameters in the Experiment

• Independent Variable: Type of pollination (Natural vs Bee‑assisted).

• Dependent Variables:

1. Fruit set percentage - fruits formed per fruit‑bearing branch.

2. Fruit drop percentage - premature falling of developing fruits.

• Controlled Parameters: Same crop (apple), same region (lower Himalayas), similar climate conditions.

(iii) Comparison and Analysis of Data

(iv) Inference from the Data

• Beekeeping promotes apple yield by increasing fruit set and reducing fruit drop.

• Pollinator management is necessary to counter the decline of natural pollinators due to climate change.

• Mixed farming provides dual benefits, such as higher apple productivity and additional income from honey.

Question 13: A student claims, “In humans, ovulation always happens on day 14 of the menstrual cycle”. Critically examine this claim and state whether the claim is correct or not. Give at least two reasons for your answer.

Answer: The claim that ovulation always happens on day 14 of the menstrual cycle is incorrect. Day 14 is only an approximate midpoint of a 28-day cycle. It is not a fixed rule for all individuals. Reason:

1. Variation in cycle length - Human menstrual cycles range from 21 to 35 days. Ovulation timing shifts depending on the total cycle length.

2. Approximate timing - Even in a 28-day cycle, ovulation occurs around day 14, not exactly on it every month. There are factors which affect the cycle, such as stress, health, and hormonal fluctuations.

Explore Class 9 Science Chapter 11 Reproduction (In-text Questions): Think It Over and Pause & Ponder

The detailed solution to all in-text exercises in this chapter is given below. Studying the NCERT Solutions Class 9 Science Chapter 11 Reproduction, Think It Over, and Pause & Ponder questions helps understand how reproduction takes place and why it is important

Think It Over

Question 1: When does a farmer prefer asexual or sexual methods of reproduction for crop production?

Answer: Farmers use asexual reproduction when they want plants to stay exactly the same as the parent.

• It keeps desirable traits unchanged because offspring are clones.

• It is fast and allows mass production of plants.

• Tissue culture gives many healthy, virus‑free plantlets.

• Crops remain uniform, and yields are reliable.

Farmers use sexual reproduction when they want new and improved varieties.

• It mixes traits from two parents to create new crops.

• Selective breeding and hybridisation make plants disease-resistant.

• It produces higher yields and stronger plants.

• Variation helps crops adapt to changing conditions.

Question 2: Why do you think most complex animals and flowering plants use sexual reproduction, while many simple organisms, like yeast and hydra, mainly reproduce asexually?

Answer: Simple organisms like yeast and hydra reproduce asexually because it is quick and needs only one parent.

• Complex animals and flowering plants reproduce sexually because it creates variation.

• Variation helps them survive diseases and adapt to changes.

• Sexual reproduction supports long-term survival and evolution.

Pause and Ponder

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Question 1: In a China rose (Hibiscus or gudhal) plant, a pollen tube grows and continues through the style after pollen lands on the stigma. Which process is about to happen next?

Answer: After the pollen tube grows through the style in the China rose, fertilisation will happen when the male gamete fuses with the egg cell.

Question 2: Look at the pictures (Fig.) of calotropis (madar) seeds and dandelion seeds given below. Can you guess what kind of seed dispersal these seeds are adapted for?

Answer: Calotropis and dandelion seeds are adapted for wind dispersal because they are light and can float in the air.

Question 3: A farmer plants two varieties of maize side by side, but notices that seeds form only when pollen from one variety reaches the stigma of the other. What type of pollination is this?

Answer: When pollen from one maize variety fertilises another variety, it is called cross-pollination.

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Question 4: Why do animals with external fertilisation generally produce more eggs than animals with internal fertilisation?

Answer: Animals with external fertilisation produce more eggs because many are lost or destroyed in the environment.

Question 5: In animals, which fertilisation method the gametes are more protected?

Answer: Gametes are more protected in internal fertilisation because it happens inside the female’s body.

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Question 6: Ravi suddenly notices that he is growing taller rapidly, his shoulders are broadening, and his voice cracks. What stage of life is he entering?

Answer: Ravi is entering puberty or adolescence stage of his life. It is the stage when the body grows quickly, and secondary sexual characteristics develop.

Question 7: Rina’s period occurs every 28 days. Her last period was on the 5th of March. On which day is she most likely to get her next period?

Answer:

• Rina’s cycle length = 28 days.

• Last period = March 5.

Next period date = Last period date + Cycle length

So, most likely she will get her next period on March 5 + 28 days = April 2.

Question 8: A human zygote has just formed. How many chromosomes does it have?

Answer: A human zygote has 46 chromosomes or 23 pairs. It is formed by combining genetic material from both parents(n+n).

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Question 9: What protective devices can be used during sexual activity to reduce the spread of STIs?

Answer: Condoms are protective devices that act as a barrier and reduce the spread of Sexually Transmitted Infections.

Question 10: If a couple uses oral contraceptive pills but not condoms, which risks remain and why?

Answer: The risk of STIs remains because pills only prevent pregnancy by changing hormones, but they do not stop infections. Condoms are needed as a physical barrier to block the transmission of diseases.

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Question 11: In many animals, the young ones can walk or find food soon after birth but human babies are completely dependent on adults for a long time. What might be some advantages and disadvantages of this for humans as a species?

Answer:

Updated NCERT Class 9 Science Chapter 11 Reproduction Topics

Topics and subtopics of this chapter are listed below. Questions are asked about these topics in the exam. To gain clarity, students can refer to the NCERT Solutions for Class 9 Science Chapter 11 Reproduction.

11.1 Asexual Reproduction

• How is vegetative propagation in plants helpful in agriculture?

11.2 Sexual Reproduction

• How does meiosis help create variations in sexual reproduction?

• Sexual reproduction in flowering plants

• How does the process of pollination occur in flowers?

• Pollination strategies and reproductive success

• Fertilisation and seed formation

11.3 Sexual Reproduction in Animals

11.4 Variations in Reproduction in Animals

11.5 Reproduction in Human Beings (Human Reproduction)

• Reproductive maturity

• What are the parts of the male reproductive system?

• What are the parts of the female reproductive system?

• How are reproductive cells made?

• What happens when a sperm meets an egg?

• What happens when an egg is not fertilised? (Menstrual Cycle)

• Pregnancy and childbirth

• Mother’s health during pregnancy

• What does it mean to be sexually mature?

• How can unwanted pregnancies and infections be prevented?

Exam Preparation Tips for NCERT Class 9 Chapter 11 Reproduction

Reproduction is an important process that provides the continuity of species and introduces variation in diversity. This Class 9 Chapter 11 Reproduction helps students understand how plants, animals and humans reproduce and why reproductive health is important. Exam preparation tips based on the NCERT Reproduction important questions are:

• Learn why offspring are genetically identical in asexual reproduction and why vegetatively propagated plants are more vulnerable to diseases.

• Practice arranging stages of reproduction in the correct order and identifying examples of self-pollination and cross-pollination.

• Explore the comparison of external vs internal fertilisation and their impact on gamete protection.

• Focus on answering questions on why menstruation stops during pregnancy, how ovulation timing varies, and the importance of maternal health.

• Study contraception methods, prevention of STIs, legal awareness and why prenatal sex determination is prohibited.