Class 9 › Science › Exploration Reproduction: How Life Continues Class 9 Science · Exploration · Chapter 11
Practice all → Summary Questions & answers Practise this chapter → View all 13 chapters, 20 charts, 16 traps corrected 27 marks: Unit I, cells to reproduction 25 marks: Unit II, mixtures to bonding 16 traps, corrected 23 marks: Unit III, motion to sound Formula cards for every law and number Motion graphs and how to read them And dozens more key concepts and formulas Only 7 pages · Page 1 free
~136 days left · Annual exams · school dates varyPreview 6 PDFs in this packCBSE Class 9 English — Kaveri Revision Kit CBSE Class 9 Hindi — Ganga Revision Kit CBSE Class 9 Mathematics Part I — Ganita Manjari Part I Revision Kit CBSE Class 9 Mathematics Part II — Ganita Manjari Part II Revision Kit CBSE Class 9 Science — Exploration Revision Kit CBSE Class 9 Social Science — Understanding Society: India and Beyond, Part I Revision Kit Marks booster Your kit Page 1 · Free Page 2 Page 2 Included in kit Page 3 Page 3 Included in kit Page 5 Page 5 Included in kit Page 6 Page 6 Included in kit Page 7 Page 7 Included in kit Tap the envelope to open your kit Preview 6 PDFs in this pack Kit cover
1 2 3 4 5 6 7 Open your kit Explore all 7 pages · Page 1 is free
All 6 Class 9 kits: where the marks sit Science: 27 marks in Unit I, the biggest unit Maths: 25 marks in Geometry, 20 in Algebra Maths: 11 identities and 12 circle theorems English: 7 grammar topics, worth 10 marks Science: 16 traps corrected, 20 charts 12-question test at the end of every kit And dozens more key concepts and facts ~7 pages per kit · Page 1 free
~136 days left · Annual exams · school dates vary
View all 8 amazing Marks Booster kits → This chapter explains how organisms produce new individuals so that life continues across generations. Reproduction is of two broad types. In asexual reproduction a single parent produces offspring that are almost exact copies (clones), with no mixing of characters; its methods include binary fission (amoeba, bacteria), budding (yeast, hydra), fragmentation (spirogyra), regeneration (planaria), spore formation (mould, ferns) and vegetative propagation in plants (by roots, stems, leaves — as in potato eyes and Bryophyllum leaves — and artificially by cuttings, layering and grafting). Asexual reproduction is fast and useful when conditions are stable, and farmers use it to keep desirable plant varieties unchanged. In sexual reproduction two parents contribute specialised sex cells called gametes; their fusion (fertilisation) forms a zygote that develops into the offspring, which inherits a mix of both parents’ characters — this variation helps populations adapt and survive change. In flowering plants the flower is the reproductive organ: pollen (male) reaches the stigma, the pollen tube carries male gametes to the ovule for fertilisation, and the ovary becomes the fruit while ovules become seeds. In humans, the male and female reproductive systems produce sperm and eggs; at puberty hormonal changes make these systems mature, the menstrual cycle prepares the female body for pregnancy, fertilisation forms a zygote that develops in the uterus, and the chapter also notes reproductive health.
Asexual reproduction
Reproduction involving a single parent and no gametes, producing offspring that are genetically identical copies of the parent.
Binary fission
An asexual method in which a single parent cell, such as amoeba, divides into two equal daughter cells.
Vegetative propagation
Asexual reproduction in plants from vegetative parts (root, stem or leaf), as in potato eyes and Bryophyllum leaf buds.
Sexual reproduction
Reproduction involving two parents and the fusion of male and female gametes, producing offspring with mixed characters.
Fertilisation
The fusion of a male gamete with a female gamete to form a zygote, which develops into a new individual.
Zygote
The single cell formed by the fusion of two gametes during fertilisation, which divides and develops into the offspring.
Q1 What is reproduction and why is it important? Answer Q2 Differentiate asexual and sexual reproduction. Answer Q3 Name four methods of asexual reproduction with an example of each. Answer Q4 What is vegetative propagation? Give two examples. Answer Q5 How do cuttings, layering and grafting differ as artificial propagation methods? Answer Q6 Why does sexual reproduction produce variation? Answer Q7 What is fertilisation? Answer Q8 Describe how a flower brings about sexual reproduction. Answer Q9 What changes occur in the human body at puberty? Answer Q10 What is the role of the menstrual cycle? Answer Q1 When does a farmer prefer asexual or sexual methods of reproduction for crops production? Answer Q2 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 Q1 1. Compare and analyse the two strategies in terms of (Table 11.3)— Pollen to seed ratio, Efficiency of pollination and seed formation Answer Q2 2. Explain why producing a very large number of pollen grains can still be an effective pollination strategy. Answer Q1 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 Q2 2. Look at the pictures (Fig. 11.16) of calotropis (madar) seeds and dandelion seeds given below. Can you guess what kind of seed dispersal these seeds are adapted for? Answer Q3 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 Q4 4. Why do animals with external fertilisation generally produce more eggs than animals with internal fertilisation? Answer Q5 5. In animals, which fertilisation method the gametes are more protected? Answer Q6 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 Q7 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 Q8 8. A human zygote has just formed. How many chromosomes does it have? Answer Q9 9. What protective devices can be used during sexual activity to reduce the spread of STIs? Answer Q10 10. If a couple uses oral contraceptive pills but not condoms, which risks remain and why? Answer Q11 11. In many animals, the young ones can walk or find food soon after birth but human babies are completely dependent for a long time. What might be some advantages and disadvantages of this for humans as a species? Answer Q1 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 Q2 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 Q3 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 Q4 4. Why does asexual reproduction produce offsprings that are genetically identical to the parent? Answer Q5 5. Explain why the menstrual cycle stops during pregnancy. Answer Q6 6. Why are flowers that bloom at night white or light in colour as compared to flowers that bloom during the day? Answer Q7 7. Why do vegetatively propagated plants tend to be more vulnerable to diseases than sexually reproduced plants? Answer Q8 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 Q9 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 Q10 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? Answer Q11 10. Suresh prepares slides with pollen grains in different sugar concentrations (0%, 2.5%, 5%, 7.5%, 10%) to study the germination of pollen. (ii) What parameters should be kept the same in this set-up? Answer Q12 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 — Tomato Stamens cover the stigma. Flowers open after pollination., Wheat Flowers open after pollination., Papaya Male and female flowers are often borne on different papaya trees. Answer Q13 12. In the lower Himalayan region of northern India, apples are an important cash crop that contribute significantly to farmer’s 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 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. 11.24, 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? Answer Q14 12. In the lower Himalayan region of northern India, apples are an important cash crop that contribute significantly to farmer’s 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 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. 11.24, 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. (ii) What are the different parameters in the experiment? Answer Q15 12. In the lower Himalayan region of northern India, apples are an important cash crop that contribute significantly to farmer’s 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 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. 11.24, 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. (iii) Compare and analyse the data of two experimental orchards Places A and B, in terms of high yields of apple fruits. Answer Q16 12. In the lower Himalayan region of northern India, apples are an important cash crop that contribute significantly to farmer’s 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 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. 11.24, 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. (iv) Based on your analysis, what do you infer from the data? Answer Q17 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
In asexual reproduction, the offspring produced are:
A Produced from gametes B Genetically identical to the single parent C Always different from the parent D A mix of two parents
Flashcards & interactive practice 
