NCERT Class 9 Science Important Chapter 11 Reproduction: How Life Continues English Medium As Per New Syllabus. NCERT Class 9 Science Important Chapter 11 Reproduction: How Life Continues Notes to each chapter is provided in the list so that you can easily browse throughout different chapter NCERT Class 9 Science Important Chapter 11 Reproduction: How Life Continues Question Answer Download PDF and select needs one. CBSE Class 9 Science Additional Solutions.
NCERT Class 9 Science Important Chapter 11 Reproduction: How Life Continues
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Reproduction: How Life Continues
Chapter – 11
| IMPORTANT QUESTION ANSWER |
Short Questions & Answers:
1. What is reproduction?
Ans: Reproduction is a biological process by which living beings produce new individuals of their own kind to ensure the continuity of life on Earth.
2. What are the two main types of reproduction?
Ans: The two main types of reproduction are asexual reproduction, where a single parent produces offspring, and sexual reproduction, where offspring inherit a mix of characteristics from two parents.
3. What is vegetative propagation?
Ans: Vegetative propagation is a type of asexual reproduction in plants where new plants arise from vegetative parts, such as the stems, roots, or leaves.
4. How does hydra reproduce asexually?
Ans: Hydra reproduces through a process called budding, where repeated cell division at a specific site produces a small outgrowth (bud) that enlarges and eventually separates from the parent body to live independently.
5. How do fungi, like bread mould, reproduce rapidly?
Ans: Fungi reproduce rapidly by producing tiny round structures called spores, which grow into new mould when they settle on a moist and warm surface.
6. What is the role of meiosis in sexual reproduction?
Ans: Meiosis is a special type of cell division that reduces the number of chromosomes by half to form gametes (sperm and eggs), ensuring that the resulting offspring has the correct number of chromosomes after fertilisation.
7. How many chromosomes are present in human cells and human gametes?
Ans: Human body cells have 46 chromosomes (23 pairs), while human gametes (sperm and eggs) have only 23 chromosomes each.
8. What are the male and female reproductive parts of a flower?
Ans: The male reproductive part of a flower is the stamen (which includes the anther and filament), and the female reproductive part is the pistil (which includes the stigma, style, and ovary).
9. Define pollination.
Ans: Pollination is the transfer of pollen grains from the anther of a flower to its stigma.
10. What is the difference between self-pollination and cross-pollination?
Ans: In self-pollination, pollen is transferred to the stigma of the same flower or another flower on the same plant. In cross-pollination, pollen is transferred to the stigma of a flower on a different plant of the same type.
11. After fertilisation in a flower, what do the ovary and ovules turn into?
Ans: After fertilisation, the ovary enlarges and develops into a fruit, while the ovules inside it develop into seeds.
12. What is the difference between external and internal fertilisation in animals?
Ans: In external fertilisation (e.g., frogs, fish), the fusion of eggs and sperm occurs outside the body in water. In internal fertilisation (e.g., reptiles, birds, mammals), the fertilisation takes place safely inside the female’s body.
13. Where are sperm produced in the human male body?
Ans: Sperm are produced in two oval-shaped organs called testes, which are located in a pouch of skin called the scrotum.
14. Why are human testes located outside the main body cavity?
Ans: The scrotum keeps the testes slightly cooler than the normal body temperature, which is essential for the proper formation of sperm.
15. What is the function of the uterus in human females?
Ans: The uterus is a bag-like structure where a fertilised egg implants, and the foetus grows, develops, and gets nourishment throughout the pregnancy.
16. What is ovulation?
Ans: Ovulation is the process in which usually one mature egg is released every month from one of the ovaries.
17. What happens in the female body if an egg is not fertilised?
Ans: If the egg is not fertilised, the thickened inner lining of the uterus sheds along with some blood and leaves the body through the vagina, a process known as menstruation or a period.
18. Who determines the biological sex of a human baby?
Ans: The biological sex of a baby is determined by the father, as he contributes either an X chromosome (resulting in an XX female) or a Y chromosome (resulting in an XY male).
19. What is In-vitro Fertilisation (IVF)?
Ans: IVF is a medical technique where an egg and a sperm are combined outside the female body in a laboratory dish, and the resulting fertilised egg is then implanted into the uterus to begin a pregnancy.
20. What are barrier methods of contraception?
Ans: Barrier methods, such as condoms or vaginal covers, physically stop sperm from reaching the egg to prevent unwanted pregnancies and can also reduce the transmission of Sexually Transmitted Infections (STIs).
Fill in the Blanks:
1. Reproduction ensures the __________ of life on Earth.
Ans: Continuity.
2. Hydra reproduces asexually by __________.
Ans: Budding.
3. The transfer of pollen from the anther to the stigma is called __________.
Ans: Pollination.
4. The male reproductive organs in humans are called __________.
Ans: Testes.
5. IVF stands for __________ Fertilisation.
Ans: In-vitro.
True or False:
1. Vegetative propagation is a type of asexual reproduction.
Ans: True.
2. Human body cells contain 23 chromosomes.
Ans: False.
3. After fertilisation, the ovary develops into a fruit.
Ans: True.
4. Barrier methods of contraception can help prevent the spread of sexually transmitted infections (STIs).
Ans: True.
5. In external fertilisation, the fusion of sperm and egg takes place inside the female body.
Ans: False.
Long Questions & Answers:
1. Explain the concept of vegetative propagation and describe any two methods used by horticulturists or farmers to grow new plants.
Ans: Vegetative propagation is an asexual mode of reproduction where new plants arise directly from the vegetative parts of a parent plant, such as the stems, roots, or leaves, without the production of seeds. Because it involves only one parent, the offspring produced are genetically identical to the parent plant. Two common methods adapted by scientists and horticulturists are cutting and grafting. In cutting, a healthy stem piece containing nodes and internodes is cut from a plant and inserted at an angle into soil mixed with compost; over time, roots and new leaves sprout from it to form a complete plant. In grafting, a healthy stem piece (from a desired plant variety) is inserted into a slit made on a rooted base plant of another variety, and the joint is protected until the tissues heal and merge, allowing farmers to combine desirable characteristics and cultivate high-yield crops on a large scale.
2. What is meiosis, and how does it contribute to genetic variation in sexually reproducing organisms?
Ans: Meiosis is a special type of cell division that occurs exclusively for sexual reproduction to form gametes, such as sperm and eggs in animals, or pollen and ovules in plants. During this process, the chromosome number of a diploid parent cell is reduced to half, meaning that human gametes end up with only 23 single chromosomes instead of the standard 46 (23 pairs). During meiosis, the chromosomes of each pair separate randomly, ensuring that every gamete receives a completely unique combination of genetic information from the parent. When male and female gametes fuse during fertilisation, they restore the full chromosome count while creating a highly unique combination of traits. This extensive random mixing creates significant genetic variation among individuals (making children different from their parents and siblings), which is crucial for species survival as it helps them adapt to changing environments and drives long-term evolution.
3. Describe the structure of a flower and explain the entire process of sexual reproduction from pollination to seed formation.
Ans: A complete flower acts as the reproductive organ in angiosperms and consists of four main whorls: sepals (outer green protective covering), petals (brightly coloured parts to attract pollinators), stamens (the male part comprising a filament and an anther that produces pollen), and the pistil (the female part comprising a stigma, a long style, and a swollen ovary containing ovules). Sexual reproduction begins with pollination, which is the transfer of pollen grains from an anther to a stigma, either within the same flower (self-pollination) or between different flowers via wind, water, or insects (cross-pollination). Once pollen lands on a compatible stigma, it germinates and grows a pollen tube down the style to reach the ovary. The male gamete travels through this tube and fuses with the egg cell inside the ovule in a process called fertilisation, forming a single-celled zygote. Post-fertilisation, the zygote develops into an embryo, the ovules transform into hard seeds, and the surrounding ovary rapidly enlarges and ripens into a fruit.
4. Compare internal and external fertilisation in animals, providing examples of each and explaining their respective survival strategies.
Ans: In animals, fertilisation—the fusion of male and female gametes—can occur either inside or outside the female’s body. External fertilisation typically takes place in aquatic environments, where the female releases eggs into the water and the male simultaneously releases sperm over them, a strategy commonly seen in frogs and most fish. Because these exposed eggs and resulting embryos face a very low chance of survival due to water currents and aquatic predators, these animals produce hundreds to thousands of eggs at a time to ensure that at least a few survive to adulthood. In contrast, internal fertilisation occurs when the sperm meets the egg safely inside the female’s reproductive tract, a method utilized by reptiles, birds, and mammals (including humans). Because the internal environment offers exceptional protection for the developing embryo or fertilised egg, the overall survival rate of the young ones is significantly higher, allowing these animals to produce a much smaller number of eggs or offspring at a time.
5. Explain the events that occur in the human female reproductive system during a typical menstrual cycle, and describe what happens if the egg is not fertilised.
Ans: In human females, the reproductive cycle, commonly known as the menstrual cycle, repeats approximately every 21 to 35 days and is centered around the preparation of the uterus for a potential pregnancy. The core event is ovulation, where usually one mature egg is released from one of the ovaries into the oviduct. In anticipation of fertilisation, the inner lining of the uterus actively thickens and becomes rich with blood vessels to prepare to receive, implant, and nourish a developing zygote. If a sperm successfully fuses with the egg, pregnancy begins, and the menstrual cycle is halted to protect the growing embryo. However, if the egg is not fertilised, it remains viable for only about a day before it degenerates. Consequently, the thickened, blood-rich uterine lining is no longer needed, so it breaks down and sheds, leaving the body along with some blood through the vagina in a process called menstruation or a period, which typically lasts 3 to 7 days before the cycle begins anew.
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