“How Do Organisms Reproduce?” is a chapter that combines conceptual biology with real-world diagrams — from binary fission in Amoeba to the structure of a flower to the human reproductive system. Board papers regularly draw both short-answer and diagram-based questions from this chapter, so building a clear, structured understanding here directly improves your Biology score.
At Convex Classes Jaipur, we teach this chapter by first building the “why” behind reproduction — why variation matters, why DNA copying must be accurate — before moving into the different modes of reproduction. This approach helps students answer even unfamiliar or twisted board questions confidently, not just the ones they’ve memorised. Below is the complete set of NCERT solutions along with deeper theory for every topic.
Chat with Convex Classes Jaipur Get Class 10 Science batch details on WhatsApp Chat Now →Why Do Organisms Reproduce? (Concept Overview)
Reproduction is the biological process by which organisms create new individuals of their own kind, ensuring the continuation of the species across generations. Unlike other life processes (like nutrition or respiration), reproduction is not essential for the survival of an individual organism, but it is absolutely essential for the survival of the species.
The chapter builds on one central idea: reproduction is fundamentally about DNA copying. Every cell contains DNA, the genetic blueprint that determines an organism’s characteristics. For an offspring to resemble its parent(s) while also allowing for gradual variation over generations, the process of DNA replication must be accurate — but not perfectly identical every single time.
Reproduction occurs in two broad categories:
- Asexual reproduction – a single parent produces offspring identical to itself (no gametes involved)
- Sexual reproduction – two parents contribute gametes that fuse to form offspring showing variation from both parents
Q1. What is the importance of DNA copying in reproduction?
Answer: Every cell contains genetic material called DNA (deoxyribonucleic acid), which carries all the information required to build and control the characteristics of an organism. During reproduction, this DNA must be copied and passed on to the next generation so that:
- The offspring inherits the basic body design and characteristic features of the parent(s).
- The species continues to exist across generations with a stable, functional body plan.
If DNA copying is highly accurate, offspring closely resemble parents. However, small errors (variations) that occur during copying are equally important — because they introduce diversity, which becomes crucial for the species’ long-term survival, especially when environmental conditions change.
Q2. Why is the variation beneficial to the species but not necessarily for the individual?
Answer: Variation refers to the differences that arise among individuals of the same species due to small inaccuracies in DNA copying during reproduction.
- For an individual, a particular variation may or may not be useful — it doesn’t guarantee that individual’s own survival.
- For the species as a whole, variation is extremely valuable because it increases the chances that at least some individuals will possess traits suited to survive a sudden environmental change (like a temperature spike, new disease, or drought).
Classic NCERT example: In a population of bacteria, if some individuals happen to have heat-resistant variations, a sudden rise in water temperature would kill most bacteria but allow the heat-resistant ones to survive and reproduce — ensuring the species doesn’t go extinct, even though many individuals perished. This shows why variation benefits the species’s long-term survival, not any one individual.
Asexual Reproduction — Detailed Theory + Solutions (Page 128)
Understanding Asexual Reproduction
In asexual reproduction, a single parent is capable of producing offspring, without the involvement of gametes (sex cells). Since only one parent is involved, the offspring produced are genetically identical (clones) to the parent, barring minor variations. Common methods include:
| Method | Description | Example |
|---|---|---|
| Fission | Cell divides into two (binary) or many (multiple) daughter cells | Amoeba, bacteria (binary); Plasmodium (multiple) |
| Budding | A small outgrowth (bud) develops on the parent and detaches as a new organism | Hydra, yeast |
| Fragmentation | Body breaks into fragments, each capable of growing into a new organism | Spirogyra |
| Regeneration | Body parts regenerate into a whole new organism if the original body is cut/injured | Planaria (flatworm) |
| Spore formation | Tiny spores are produced in sporangia and released, germinating into new individuals under favourable conditions | Rhizopus (bread mould) |
| Vegetative propagation | New plants grow from vegetative parts like roots, stems, or leaves | Potato, Bryophyllum |
Q1. How does binary fission differ from multiple fission?
Answer:
| Basis | Binary Fission | Multiple Fission |
|---|---|---|
| Number of daughter cells | Splits into exactly two equal daughter cells | Splits into many daughter cells simultaneously |
| Nuclear division | Single nuclear division followed by cytoplasmic division | Multiple nuclear divisions occur first, followed by simultaneous cytoplasmic division |
| Example | Amoeba, Paramecium, bacteria | Plasmodium (malarial parasite) |
Q2. How will an organism be benefited if it reproduces through spores?
Answer: Reproduction through spores offers several survival advantages:
- A single sporangium (spore-producing structure) can produce a very large number of spores at once, greatly increasing reproductive output.
- Spores are lightweight and can be dispersed over long distances by air or water, helping the species colonise new areas and reducing competition for resources at the original location.
- Spores are protected by thick, resistant walls that allow them to survive harsh or unfavourable environmental conditions (like dryness or heat) until conditions improve for germination.
Q3. Why can’t more complex organisms give rise to new individuals through regeneration?
Answer: Complex, multicellular organisms have highly specialised organ systems (nervous, circulatory, digestive, etc.), where different organs are interdependent and finely coordinated to keep the organism functioning as a whole. This high degree of specialisation means these organisms have lost the ability to regrow an entire new individual from just a body fragment.
However, many complex organisms retain limited regenerative ability — for instance, humans can regenerate skin, blood cells, and some liver tissue, but cannot regenerate an entire limb or organ system the way a simple organism like Planaria can regenerate its whole body from a small cut piece.
Q4. Why is vegetative propagation practised for growing some types of plants?
Answer: Vegetative propagation — growing new plants from vegetative parts like stems, roots, or leaves — is preferred for certain crops because:
- Certain plants like banana, orange, and pineapple produce seedless fruits or non-viable seeds, making seed-based propagation impossible.
- It is a faster, cheaper, and easier method compared to growing plants from seeds.
- It allows cultivation in situations where natural seed germination fails or is unreliable.
- Since all offspring are genetically identical to the parent, it helps preserve desirable characteristics (like fruit quality, disease resistance) of a particular variety across generations — something seed propagation cannot guarantee due to variation.
Q5. Why is DNA copying an essential part of the process of reproduction?
Answer: DNA copying (replication) ensures that the genetic instructions responsible for an organism’s characteristics are accurately transmitted from parent to offspring. During cell division, DNA is first copied, producing two identical sets, along with an additional cellular apparatus; only then does the cell divide into two daughter cells, each receiving a complete copy of DNA. Without accurate DNA copying, offspring would not develop the correct body structure or functions inherited from the parent — making it the foundational step of all reproduction, whether asexual or sexual.
Sexual Reproduction — Detailed Theory + Solutions (Page 140)
Understanding Sexual Reproduction
Sexual reproduction involves two parents contributing gametes (sex cells) — a male gamete and a female gamete — which fuse together in a process called fertilisation to form a zygote. This zygote develops into a new offspring that carries a combination of characteristics from both parents, resulting in genetic variation. This variation is a major evolutionary advantage, as it improves the species’ ability to adapt to changing environments.
Q1. How is the process of pollination different from fertilisation?
Answer:
| Basis | Pollination | Fertilisation |
|---|---|---|
| Definition | Transfer of pollen grains from the anther (male part) to the stigma (female part) | Fusion of male and female gametes to form a zygote |
| Agents involved | Wind, water, insects, or other pollinators | Occurs internally, within the ovule |
| Result | Enables pollen tube growth towards the ovule | Forms a zygote, which develops into an embryo |
| Location | Occurs on the stigma | Occurs inside the ovule |
Q2. What is the role of the seminal vesicles and the prostate gland?
Answer: The seminal vesicles and prostate gland are accessory glands of the human male reproductive system. Their secretions:
- Provide a nutrient-rich fluid medium (containing fructose, calcium, and certain enzymes) that nourishes and helps transport sperm.
- Make the medium suitable for the survival and motility of sperm, allowing them to travel efficiently through the reproductive tract.
Q3. What are the changes seen in girls at the time of puberty?
Answer: Puberty in girls (roughly between ages 10-14) is marked by several physical and physiological changes controlled by reproductive hormones:
- Growth of hair in the genital area and underarms
- Increase in the size of the uterus and ovaries
- Development and enlargement of breasts, along with darkening of the skin around the nipples
- Onset of the menstrual cycle
- Increased oil secretion from skin glands, sometimes leading to acne
Exam tip (Convex Classes Jaipur): CBSE often pairs this with a similar question on puberty changes in boys (growth of facial/body hair, deepening of voice, broadening of shoulders) — prepare both together as a comparison for full marks.
Q4. How does the embryo get nourishment inside the mother’s body?
Answer: After fertilisation, the embryo implants itself in the thickened lining of the uterus. Nourishment is provided through a specialised structure called the placenta, which:
- Is embedded in the uterine wall and contains finger-like projections called villi on the embryo’s side, increasing the surface area for exchange.
- Has large blood spaces on the mother’s side that surround the villi, allowing glucose, oxygen, and other essential nutrients to pass from the mother’s blood to the embryo.
- Also facilitates the removal of waste products from the embryo’s blood into the mother’s blood for excretion.
Q5. If a woman is using a Copper-T, will it help in protecting her from sexually transmitted diseases?
Answer: No. A Copper-T is an intrauterine contraceptive device that works by preventing implantation/fertilisation, but it does not create a barrier that prevents contact between body fluids. Since sexually transmitted infections spread through such contact, Copper-T offers no protection against them. Only barrier methods, like condoms, help prevent the transmission of sexually transmitted infections.
NCERT Exercise Solutions (Page 141)
1. Asexual reproduction takes place through budding in:
(b) Yeast — A small outgrowth (bud) forms on the parent yeast cell, gradually enlarges, and eventually detaches to form a new, independent organism.
2. Which of the following is not a part of the female reproductive system?
(c) Vas deferens — This is a part of the male reproductive system; it is a muscular tube that transports mature sperm from the epididymis to the urethra.
3. The anther contains:
(d) Pollen grains — The anther is the male reproductive part of a flower, containing microspores that develop into pollen grains (the male gametophyte).
4. What are the advantages of sexual reproduction over asexual reproduction?
Answer:
- The offspring inherits a combination of characteristics from both parents, leading to genetic variation.
- Increased variation improves the survival and adaptability of the species under changing environmental conditions.
- Offspring can adapt more effectively to new or fluctuating environments compared to genetically identical clones.
- It generally contributes to overall species health and evolutionary progress over generations.
5. What are the functions performed by the testis in human beings?
Answer:
- Production of sperm (male gametes).
- Secretion of the hormone testosterone, which is responsible for the development of secondary sexual characteristics in males (such as facial hair, deepening of voice, and muscle development) during puberty.
6. Why does menstruation occur?
Answer: Every month, one of the ovaries releases a mature egg (ovulation), while simultaneously the uterine lining thickens with blood vessels to prepare for a potential pregnancy. If the released egg is not fertilised by sperm, this thickened lining is no longer needed. It gradually breaks down and is shed from the body along with some blood — this shedding process is called menstruation, and it typically occurs roughly every 28 days from puberty until menopause.
7. Draw a labelled diagram of the longitudinal section of a flower.
Answer: A well-labelled diagram should clearly show: sepals, petals, the stamen (anther + filament — male part), and the pistil/carpel (stigma + style + ovary containing ovules — female part). Practising this diagram from your NCERT textbook and labelling all parts accurately is essential, as this question is frequently asked for 3-5 marks in board exams.
8. What are the different methods of contraception?
Answer: Methods of contraception are broadly classified as:
| Method Type | Examples | Mechanism |
|---|---|---|
| Natural/behavioural | Avoiding intercourse during the fertile period of the menstrual cycle | Reduces chances of sperm-egg contact during ovulation |
| Barrier methods | Condoms (male & female), diaphragms, cervical caps | Physically prevent sperm from reaching the egg |
| Oral contraceptives | Hormonal pills | Alter hormonal balance to prevent ovulation |
| Intrauterine devices | Copper-T, loop | Prevent successful implantation/fertilisation in the uterus |
| Surgical methods | Tubectomy (in females), vasectomy (in males) | Permanently block the fallopian tubes or vas deferens to prevent gamete transport |
9. How are the modes of reproduction different in unicellular and multicellular organisms?
Answer: Unicellular organisms mainly reproduce through simple asexual methods like fission (binary or multiple) and budding, where the single cell itself divides or buds to form new individuals. Multicellular organisms, having specialised organ systems, use more complex modes such as spore formation, vegetative propagation, and regeneration (in simpler multicellular forms), while highly complex multicellular organisms like humans and most animals reproduce exclusively through sexual reproduction, involving specialised reproductive organs and gametes.
10. How does reproduction help in providing stability to populations of species?
Answer: Reproduction ensures that a species continuously produces new individuals to replace those lost due to death, predation, or disease. By maintaining a balance between the birth rate and death rate, reproduction helps sustain a stable population size for a species over time, preventing the species from becoming extinct and helping maintain overall ecological balance.
11. What could be the reasons for adopting contraceptive methods?
Answer:
- To control population growth, particularly at a national/societal level.
- To avoid unplanned or unwanted pregnancies.
- To prevent the transmission of sexually transmitted infections (in the case of barrier methods specifically).
Reproduction Class 10 – Quick Revision Notes
- Reproduction = biological process of producing new individuals to sustain a species (not essential for individual survival)
- Asexual reproduction = one parent, no gametes, offspring genetically identical → fission, budding, fragmentation, regeneration, spore formation, vegetative propagation
- Sexual reproduction = two parents, gametes fuse via fertilisation, offspring show variation
- In plants: pollination (anther → stigma) → fertilisation (in ovule) → zygote → embryo; ovule becomes seed, ovary becomes fruit
- In humans: testis produces sperm + testosterone; ovary produces eggs; placenta nourishes embryo; menstruation occurs when the egg is not fertilised
- Contraception methods: natural, barrier, oral/hormonal, intrauterine devices, surgical
Frequently Asked Questions (FAQs)
Q1. What are the two main types of reproduction covered in Class 10 Science Chapter 8?
Ans. The chapter covers asexual reproduction (fission, budding, fragmentation, regeneration, spore formation, vegetative propagation) and sexual reproduction (involving gamete formation and fertilisation in plants and humans).
Q2. Is this chapter important for CBSE Class 10 board exams?
Ans. Yes, it is a high-weightage Biology chapter. Diagram-based questions (flower structure, human reproductive organs) and comparison questions (asexual vs sexual reproduction, binary vs multiple fission) appear regularly in board papers.
Q3. What is the difference between pollination and fertilisation?
Ans. Pollination is the physical transfer of pollen grains from the anther to the stigma, while fertilisation is the actual fusion of the male and female gametes to form a zygote, which happens after pollination inside the ovule.
Q4. How can Convex Classes Jaipur help me prepare this chapter better?
Ans. At Convex Classes Jaipur, our faculty teach this chapter with labelled diagram practice, structured comparison tables, and CBSE marking-scheme-aligned answer writing, along with regular tests and doubt-clearing sessions to help you retain concepts confidently for the board exam.
Q5. Why is variation important in sexual reproduction?
Ans. Variation ensures offspring are not identical to their parents, which increases the chances that some individuals in a population carry traits suited to survive changing environmental conditions — this is essential for the long-term survival of a species.
This content has been prepared by the academic team at Convex Classes Jaipur for educational purposes, strictly following the CBSE/NCERT Class 10 Science syllabus.
