Class 10 Science Ch 7: How do Organisms Reproduce? Notes
MP Board Class 10 Science Chapter 7: How do Organisms Reproduce? Important Questions — This chapter covers the fascinating world of reproduction in organisms — from binary fission in amoeba to sexual reproduction in humans. With 6-7 marks weightage in the MP Board exam, this chapter requires understanding of each reproductive process, diagrams, and key differences between asexual and sexual reproduction. Here are the most important questions curated from past board exams (2018-2026).
📑 Table of Contents
🧬 1. Introduction to Reproduction
Q1. What is reproduction? Why is it essential for organisms?
Answer: Reproduction is the biological process by which living organisms produce offspring of their own kind. It is essential because:
- It ensures the continuity of species from one generation to the next
- It prevents the extinction of species
- It introduces genetic variation (in sexual reproduction) which helps in evolution
- It maintains the population of species in nature
Q2. Differentiate between asexual and sexual reproduction.
Answer: The key differences are:
🔬 2. Asexual Reproduction Methods
Q3. Explain binary fission with an example. How is it different from multiple fission?
Answer: Binary fission is a type of asexual reproduction where a parent cell divides into two equal daughter cells. The nucleus divides first (karyokinesis), followed by cytoplasm division (cytokinesis). Example: Amoeba, Paramoecium, Bacteria (e.g., E. coli).
Difference from Multiple Fission: In binary fission, the parent divides into two daughter cells. In multiple fission, the parent nucleus divides repeatedly to form many nuclei, and then the cytoplasm divides to produce many daughter cells simultaneously. Example of multiple fission: Plasmodium (malaria parasite).
Q4. What is budding? Give examples of organisms that reproduce by budding.
Answer: Budding is a form of asexual reproduction where a small outgrowth (bud) develops on the parent body. The bud grows, develops its own nucleus and organelles, and eventually detaches to form a new independent organism.
Examples: Hydra (freshwater organism), Yeast (fungus). In Hydra, the bud develops as a small projection, grows tentacles, and detaches when fully formed. In yeast, the bud may detach immediately or form a chain of buds.
Q5. Describe fragmentation and regeneration. Give one example of each.
Answer:
- Fragmentation: The parent body breaks into two or more fragments, each of which grows into a complete organism. Example: Spirogyra (algae), Planaria. When Spirogyra filament breaks, each fragment grows into a new filament.
- Regeneration: The ability of an organism to regrow lost body parts. Some organisms can regenerate entire bodies from small pieces. Example: Planaria (flatworm), Hydra, Starfish. If a Planaria is cut into pieces, each piece can regenerate into a complete worm.
Q6. What is spore formation? How do fungi reproduce through spores?
Answer: Spore formation is a method of asexual reproduction where the parent produces microscopic reproductive units called spores. Each spore is covered by a protective wall that allows survival in unfavourable conditions.
In fungi like Rhizopus (bread mould), the hyphae develop bulbous structures called sporangia at their tips. Inside each sporangium, thousands of spores are produced. When the sporangium bursts, spores are released into the air. Under favourable conditions (moisture, warmth, food), each spore germinates to form a new fungus.
🌱 3. Sexual Reproduction in Plants
Q7. Label the parts of a flower and explain the function of each reproductive part.
Answer: A typical flower has the following major parts:
Q8. Define pollination. Differentiate between self-pollination and cross-pollination.
Answer: Pollination is the transfer of pollen grains from the anther (male part) to the stigma (female part) of a flower.
Self-pollination: Pollen is transferred from the anther to the stigma of the same flower or another flower on the same plant. Examples: Pea, Wheat, Rice.
Cross-pollination: Pollen is transferred from the anther of one flower to the stigma of a flower on a different plant of the same species. Examples: Apple, Mango, Sunflower.
Agents of cross-pollination: Wind (anemophily), Insects/bees (entomophily), Birds (ornithophily), Water (hydrophily).
Q9. Explain the process of fertilization in a flowering plant.
Answer: Fertilization in flowering plants (also called double fertilization) occurs as follows:
- After pollination, the pollen grain germinates on the stigma and produces a pollen tube
- The pollen tube grows through the style and reaches the ovule inside the ovary
- Two male gametes (sperm cells) travel down the pollen tube
- One male gamete fuses with the egg cell → forms zygote (2n) → develops into embryo
- The second male gamete fuses with two polar nuclei → forms triploid endosperm (3n) → provides nutrition to the embryo
- This double fusion is called double fertilization — unique to angiosperms
- Ovule develops into seed, ovary develops into fruit
👤 4. Sexual Reproduction in Humans
Q10. Draw and label the male reproductive system. Write the functions of each part.
Answer: The male reproductive system consists of:
Q11. Draw and label the female reproductive system. Describe the path of an egg.
Answer: The female reproductive system comprises:
Path of an egg: Ovary (released during ovulation) → Fallopian tube (fertilization occurs here if sperm present) → Uterus (implantation if fertilized) or expelled during menstruation (if not fertilized).
Q12. What is the menstrual cycle? Explain its key phases.
Answer: The menstrual cycle is a monthly reproductive cycle in human females (approximately 28 days) that prepares the uterus for pregnancy. Key phases:
- Menstrual phase (Days 1-5): The uterine lining (endometrium) breaks down and is shed as blood and tissue through the vagina (menstruation)
- Follicular phase (Days 6-13): A new egg matures in the ovary; the uterine lining begins to thicken
- Ovulation (Day 14): The mature egg is released from the ovary into the fallopian tube
- Luteal phase (Days 15-28): Uterine lining continues to thicken. If fertilization does not occur, the lining breaks down and the cycle repeats
Q13. Describe the process of fertilization and implantation in humans.
Answer: Fertilization occurs in the fallopian tube. When sperm reach the egg, the head of the sperm penetrates the egg membrane, and the nuclei fuse to form a zygote (diploid cell). The zygote undergoes repeated mitotic divisions (cleavage) as it moves towards the uterus, forming a ball of cells (morula → blastocyst). The blastocyst implants itself into the thickened uterine lining (endometrium) — this is called implantation (around day 6-7 after fertilization). After implantation, the placenta develops to provide nutrition and oxygen to the embryo.
🩺 5. Reproductive Health & Contraception
Q14. What are contraceptive methods? Classify them with examples.
Answer: Contraceptive methods are techniques used to prevent unwanted pregnancy. They are classified as:
Q15. Why is the use of condoms recommended in addition to preventing pregnancy?
Answer: Condoms are recommended because they provide dual protection: (1) They prevent unwanted pregnancy by acting as a physical barrier, and (2) They protect against Sexually Transmitted Infections (STIs) such as HIV/AIDS, Gonorrhea, Syphilis, and Chlamydia. Other contraceptive methods (like oral pills or IUDs) only prevent pregnancy and offer no protection against STIs.
📝 6. Multiple Choice Questions (1 Mark Each)
Multiple Choice Questions from this chapter appear frequently in the MP Board exam. Practice these 10 MCQs to secure full marks.
- Which of the following is an example of asexual reproduction?
(a) Binary fission in Amoeba ✓ (b) Fertilization in humans (c) Pollination in flowers (d) Menstruation in females - The male gamete in humans is called:
(a) Ovum (b) Sperm ✓ (c) Zygote (d) Embryo - The site of fertilization in humans is:
(a) Uterus (b) Ovary (c) Fallopian tube ✓ (d) Vagina - Which part of the flower becomes the fruit?
(a) Stigma (b) Ovary ✓ (c) Petal (d) Anther - Fragmentation is observed in:
(a) Hydra (b) Amoeba (c) Spirogyra ✓ (d) Yeast - Spore formation occurs in:
(a) Amoeba (b) Rhizopus (Bread mould) ✓ (c) Hydra (d) Planaria - The hormone that triggers the development of male secondary sexual characteristics is:
(a) Oestrogen (b) Progesterone (c) Testosterone ✓ (d) Insulin - Double fertilization is a characteristic feature of:
(a) Gymnosperms (b) Angiosperms ✓ (c) Pteridophytes (d) Bryophytes - Which contraceptive method also protects against STDs?
(a) Copper-T (b) Oral pills (c) Condom ✓ (d) Vasectomy - The average duration of the menstrual cycle is:
(a) 14 days (b) 21 days (c) 28 days ✓ (d) 35 days
✏️ 7. Very Short & Short Answer Questions (2–4 Marks)
-
List two reasons why reproduction is essential for living organisms.
Reproduction ensures continuity of species and introduces genetic variation that drives evolution. (2 marks) -
Name the asexual reproductive structure in: (a) Hydra (b) Rhizopus
(a) Hydra — Bud; (b) Rhizopus — Sporangium (produces spores). (2 marks) -
What are the two functions of the testes in humans?
The testes produce male gametes (sperm) and secrete the male hormone testosterone, which regulates male secondary sexual characteristics. (2 marks) -
Write two differences between self-pollination and cross-pollination.
Self-pollination: pollen from same flower/plant; no external agent needed. Cross-pollination: pollen from different plant; requires wind, insects, or other agents. (2 marks) -
Define the term ‘regeneration’. Name an organism that shows this phenomenon.
Regeneration is the ability of an organism to regrow damaged or lost body parts. Example: Planaria (a flatworm can regenerate into a complete organism from a small fragment). (2 marks) -
What happens when: (a) A mature egg is not fertilized? (b) A mature egg gets fertilized?
(a) The uterine lining breaks down and menstruation occurs. (b) The zygote undergoes cleavage, forms a blastocyst, and implants in the uterus — pregnancy begins. (3 marks) -
Explain the role of the placenta in human development.
The placenta is a disc-like structure attached to the uterine wall and connected to the embryo via the umbilical cord. It supplies oxygen and nutrients to the embryo, removes waste products, and produces hormones (like hCG) that maintain pregnancy. (3 marks) -
Differentiate between binary fission in Amoeba and Paramoecium.
In Amoeba, binary fission occurs irregularly in any plane. In Paramoecium, binary fission occurs transversely (at right angles to the long axis). (2 marks)
📖 8. Long Answer Questions (5–6 Marks)
Q1. Describe the process of reproduction in Hydra through a labelled diagram. Compare it with reproduction in Amoeba.
Answer: Hydra reproduces asexually through budding. A small outgrowth called a bud develops on the Hydra’s body. The bud contains an extension of the gastrovascular cavity. Cells divide and differentiate to form tentacles and a mouth. Once fully developed, the bud constricts at the base and detaches from the parent to live as an independent organism. This usually takes several days.
Comparison with Amoeba (Binary Fission): In Amoeba, the parent cell simply splits into two equal halves by binary fission — no specialized growth or differentiation occurs. Hydra budding involves organized cell division and development of specialized structures (tentacles, mouth). Binary fission in Amoeba produces two identical daughter cells in a few hours, while Hydra budding produces one offspring over several days. Importantly, both produce genetically identical offspring since they are forms of asexual reproduction. (5 marks)
Q2. Explain the events that occur in a flower after pollination leads to seed and fruit formation. Describe double fertilization in angiosperms.
Answer: After a pollen grain lands on the stigma, the following sequence of events occurs:
- Germination of pollen: The pollen grain absorbs moisture and nutrients from the stigma and produces a pollen tube that grows down through the style toward the ovary.
- Double Fertilization: Two male gametes travel through the pollen tube. One male gamete fuses with the egg cell (n) to form the diploid zygote (2n). The second male gamete fuses with the two polar nuclei (n + n = 2n) to form triploid primary endosperm nucleus (3n). This is called double fertilization — unique to angiosperms (flowering plants).
- Post-fertilization changes: The zygote develops into the embryo. The primary endosperm nucleus divides to form endosperm tissue that provides nutrition to the developing embryo. The ovule develops into the seed, and the ovary wall develops into the fruit. The petals, sepals, stamens, and style wither and fall off.
Result: A seed contains the embryo (future plant) and stored food (endosperm), protected by a seed coat (from the ovule wall). The fruit (from the ovary) protects the seeds and helps in their dispersal. (6 marks)
Q3. Draw a labelled diagram of the human female reproductive system. Describe the process of fertilization, implantation, and development of the embryo up to the foetal stage.
Answer: The human female reproductive system consists of ovaries (produce eggs), fallopian tubes (site of fertilization), uterus (where embryo develops), cervix, and vagina.
Fertilization to Foetal Development:
- Fertilization: During ovulation (around day 14 of the menstrual cycle), a mature egg is released from the ovary into the fallopian tube. If sperm are present from sexual intercourse, one sperm penetrates the egg membrane, and their nuclei fuse to form a diploid zygote.
- Cleavage and Morula: The zygote undergoes rapid mitotic divisions (cleavage) as it travels down the fallopian tube. A solid ball of 16-32 cells called the morula is formed.
- Blastocyst Formation: The morula develops into a hollow ball of cells called the blastocyst, with an inner cell mass (which will form the embryo) and an outer layer (trophoblast).
- Implantation: Around day 6-7 after fertilization, the blastocyst attaches to and embeds itself into the thickened uterine lining (endometrium). This is called implantation.
- Embryonic Development: The inner cell mass differentiates into three germ layers (ectoderm, mesoderm, endoderm) from which all organs develop. The placenta forms from the trophoblast and the uterine tissue, providing nutrients and oxygen through the umbilical cord.
- Foetal Stage: After 8 weeks of development, the embryo is called a foetus. All major organ systems are formed. The foetus continues to grow for the remaining 7 months of pregnancy (total gestation: approximately 40 weeks / 9 months).
Birth: At the end of gestation, hormones trigger labour — contractions of the uterus push the baby out through the cervix and vagina (birth canal). (6 marks)
📋 Previous Year Questions (2018–2026)
The following questions have appeared in MP Board Class 10 Science board exams:
❓ Frequently Asked Questions
Q1. Is How do Organisms Reproduce a difficult chapter?
It is a moderate difficulty chapter. Most students find the diagrams (male/female reproductive systems) and double fertilization challenging. With proper revision of processes and labelled diagrams, scoring 6-7/7 marks is very achievable.
Q2. What are the most important topics from this chapter for MP Board 2027?
Key topics: Differences between asexual and sexual reproduction, binary fission and budding, male and female reproductive system diagrams, double fertilization in plants, contraceptive methods, and the menstrual cycle.
Q3. How many marks does this chapter carry in the MP Board exam?
Chapter 7 (How do Organisms Reproduce) typically carries 6-7 marks — approximately 5 marks for long answer/diagram questions and 1-2 marks for MCQs or short-answer questions.
Q4. Do I need to remember all diagram labels?
Yes. Labelled diagrams of the male reproductive system, female reproductive system, flower structure, and Hydra budding are frequently asked. Practice drawing them with correct labels at least 3-4 times before the exam.
Q5. What is the difference between fission and fragmentation?
In fission (e.g., Amoeba binary fission), a single-celled organism divides into two or more cells. In fragmentation (e.g., Spirogyra, Planaria), a multicellular organism breaks into fragments, each growing into a complete organism. Fission is unicellular; fragmentation is multicellular.
Q6. Why is reproduction not necessary for an individual organism’s survival?
Individual organisms can survive without reproducing — an organism’s survival depends on nutrition, respiration, and other life processes. However, reproduction is essential for the species to continue and prevent extinction.
Q7. What is the difference between a zygote and an embryo?
A zygote is the single-celled fertilized egg formed immediately after the fusion of sperm and egg. After the zygote undergoes multiple cell divisions (cleavage), it develops into an embryo — a multicellular structure that will eventually differentiate into all body tissues and organs.
Q8. What are sexually transmitted infections (STIs)? Name two common ones.
STIs are infections that are transmitted through sexual contact. Common STIs include Gonorrhoea (caused by bacteria Neisseria gonorrhoeae) and Syphilis (caused by Treponema pallidum). HIV/AIDS is the most dangerous STI. Using condoms can prevent STIs.
Q9. How long does the development of a human foetus take?
Human gestation (pregnancy) lasts approximately 40 weeks or 9 months (280 days from the last menstrual period). The embryonic stage covers the first 8 weeks, and the foetal stage covers from 9 weeks until birth.
Q10. What is vegetative propagation? Give an example.
Vegetative propagation is a type of asexual reproduction in plants where new plants grow from vegetative parts like stems, roots, or leaves. Examples: Potato (from tuber — underground stem), Bryophyllum (leaf buds), Onion (bulb), Ginger (rhizome).
Q11. What is the advantage of sexual reproduction over asexual reproduction?
Sexual reproduction creates genetic variation because offspring inherit a mix of genes from both parents. This variation helps populations adapt to changing environments and is the raw material for evolution. Asexual reproduction produces identical clones with no variation.
Q12. Why does menstruation occur?
Menstruation occurs when a released egg is not fertilized. The uterine lining (endometrium), which had thickened to support a potential pregnancy, breaks down and is shed through the vagina along with blood and mucus. This cycle repeats approximately every 28 days in human females of reproductive age.