How Do Organisms Reproduce — Class 10 Biology NCERT Solutions (Free)
Free step-by-step NCERT solutions for Class 10 Biology chapter "How Do Organisms Reproduce" — 8 important questions with detailed answers for CBSE board exam preparation.
TL;DR: Free step-by-step NCERT solutions for Class 10 Biology chapter "How Do Organisms Reproduce" — 8 important questions with detailed answers for CBSE boa…
Written & reviewed by the Syllab.in Academic Team (CBSE/NCERT subject experts) · Updated
NCERT Solutions for Class 10 Biology — How Do Organisms Reproduce. Step-by-step answers to all 8 textbook questions from this chapter, written for CBSE board preparation and free to use.
How Do Organisms Reproduce — All 8 Questions Solved
Q1. Define reproduction. Distinguish between asexual and sexual reproduction.
Reproduction is the biological process by which organisms produce new individuals of the same species.
Asexual reproduction:
- Involves only one parent
- No fusion of gametes
- Offspring genetically identical to parent (clones)
- Produces large number of offspring quickly
- No variation (genetic diversity low)
- Examples: bacteria fission, budding in hydra, fragmentation in starfish, vegetative reproduction in plants
- Advantages: rapid population growth, requires less energy, no mate needed
- Disadvantages: no genetic variation, population susceptible to disease
Sexual reproduction:
- Involves two parents (usually male and female)
- Fusion of two gametes (sperm and egg) to form zygote
- Offspring genetically different from parents (genetic recombination)
- Produces fewer offspring
- Results in genetic variation
- Examples: flowers, animals with male and female
- Advantages: genetic diversity, adaptation to environment, reduces harmful mutations
- Disadvantages: requires energy, time, and usually a mate
Key difference: Asexual produces identical copies; sexual produces genetically unique offspring.
Q2. Describe the different modes of asexual reproduction in animals and plants with examples.
Asexual reproduction modes:
In animals:
1. Binary fission:
- One organism divides into two
- Example: bacteria, some protozoans
- Process: DNA replication, then cell division
2. Budding:
- New organism grows as outgrowth from parent
- Bud detaches and becomes independent
- Example: hydra, yeast
3. Fragmentation:
- Organism breaks into fragments
- Each fragment grows into new organism
- Example: starfish, planaria (flatworm)
4. Regeneration:
- Lost body parts regrow
- Some organisms regrow entire body from fragment
- Example: hydra, earthworm (limited)
In plants:
1. Vegetative propagation:
- Using vegetative parts (roots, stems, leaves)
- Examples:
a) Tubers: potato
b) Runners: strawberry
c) Bulbs: onion, tulip
d) Fragmentation: bryophyllum leaves
2. Spore formation:
- Production of spores by meiosis
- Spores germinate into new plants
- Example: ferns, mosses
3. Micropropagation (tissue culture):
- Growing plants from single cell or tissue in lab
- Example: orchids, banana
All these modes produce genetically identical offspring.
Q3. What is a flower? Describe the structure of a flower and name the male and female reproductive parts.
A flower is the reproductive structure of flowering plants (angiosperms).
Structure of a flower:
Accessory parts (not directly involved in reproduction):
1. Sepals - green leaf-like structures that protect flower bud
- Collectively called calyx
2. Petals - colorful structures that attract pollinators
- Collectively called corolla
Essential reproductive parts:
Male reproductive part - Stamen (androecium):
1. Filament - thin stalk supporting anther
2. Anther - produces and contains pollen (male gamete)
- Contains pollen sacs with pollen grains
- Each pollen grain contains two nuclei: generative nucleus and vegetative nucleus
Female reproductive part - Carpel or Pistil (gynoecium):
1. Stigma - topmost part, receives pollen during pollination
2. Style - connects stigma to ovary
3. Ovary - at base of pistil, contains ovules
- Ovules contain female gamete (egg cell)
- Develops into fruit after fertilization
In a complete flower, both male (stamen) and female (carpel) parts are present.
In an incomplete flower, one type may be missing or non-functional.
The anther produces pollen; the ovary produces ovules. Pollination and fertilization lead to seed and fruit formation.
Q4. Explain pollination and fertilization in flowering plants. What is the difference between them?
Pollination:
- Definition: Transfer of pollen from anther to stigma
- Process:
1. Pollen grain lands on stigma (or falls on stigma)
2. Pollen grain sticks to stigma surface
- Type: mechanical process only, no fusion of cells yet
- Agents: wind, insects, water, gravity
- Wind pollination: usually small, dry pollen; flowers lack bright petals or scent
- Insect pollination: bright petals, sweet scent, nectar to attract insects
- Result after pollination: Pollen tube grows down through style towards ovary
Fertilization:
- Definition: Fusion of male gamete (pollen nucleus) with female gamete (egg) to form zygote
- When it occurs: After pollen tube reaches ovule
- Process:
1. Pollen tube enters ovule through micropyle
2. Generative nucleus divides to form two sperm cells
3. One sperm fuses with egg cell to form zygote (2n)
4. Other sperm fuses with polar nuclei to form endosperm (3n) for nutrition
5. This double fertilization is unique to flowering plants
- Result: Zygote develops into embryo; endosperm becomes seed food storage; ovule becomes seed; ovary becomes fruit
Key difference:
- Pollination = pollen transfer (mechanical, doesn't involve fusion)
- Fertilization = fusion of gametes (biological, produces zygote)
Both are necessary for seed and fruit formation in flowering plants.
Q5. Describe the structure and function of the human male reproductive system.
Male reproductive system structures and functions:
External structures:
1. Penis - delivers sperm into female; contains urethra
2. Scrotum - pouch of skin containing testes; maintains low temperature for sperm production
Internal structures:
1. Testes (gonads):
- Pair of oval glands in scrotum
- Function: Produce sperm through spermatogenesis
- Also produce testosterone hormone
- About 300 million sperm produced daily
2. Epididymis:
- Coiled tube above each testis
- Stores and matures sperm
- Sperm takes 2-3 weeks to mature and acquire motility
3. Vas deferens (ductus deferens):
- Tube carrying sperm from epididymis
- Travels through inguinal canal into abdomen
4. Seminal vesicles:
- Glands producing seminal fluid (60% of semen)
- Contains fructose for sperm energy
5. Prostate gland:
- Produces milky alkaline secretion (30% of semen)
- Protects sperm in acidic female vagina
6. Bulbourethral glands:
- Produce clear mucus to neutralize urethra
7. Urethra:
- Tube carrying sperm through penis
- Also carries urine
Semen: Mixture of sperm and glandular secretions; volume ~5 mL per ejaculation
Hormonal control: FSH and LH from pituitary; testosterone from testes maintains secondary sexual characteristics
Q6. Describe the structure and function of the human female reproductive system.
Female reproductive system structures and functions:
External structures (vulva):
1. Labia majora - outer folds of skin
2. Labia minora - inner folds
3. Clitoris - sensitive structure
4. Vaginal opening - entrance to vagina
Internal structures:
1. Vagina:
- Muscular canal receiving penis during intercourse
- Receives sperm
- Elastic walls, acidic pH protects against infection
2. Cervix:
- Narrow opening of uterus into vagina
- Produces mucus; thicker during infertile days
3. Uterus (womb):
- Hollow muscular organ
- Receives fertilized egg for implantation
- Endometrium (inner lining) thickens each cycle
- Contractions during labor expel fetus
4. Fallopian tubes (oviducts):
- Pair of tubes extending from uterus
- Fertilization occurs in fallopian tube
- Cilia move egg towards uterus
5. Ovaries (gonads):
- Pair of almond-shaped glands
- Function: Produce egg cells through oogenesis
- Produce estrogen and progesterone hormones
- One egg released each menstrual cycle (~400 eggs in lifetime)
Menstrual cycle (28 days):
- Menstruation (days 1-5): Endometrium sheds
- Follicular phase (days 1-14): Estrogen rises, egg develops
- Ovulation (day 14): Egg released from ovary
- Luteal phase (days 15-28): Progesterone rises, uterus prepares for implantation
- If fertilization doesn't occur, cycle repeats
Hormonal control: FSH promotes follicle development; LH triggers ovulation; estrogen and progesterone regulate uterine lining
Q7. What are contraceptive methods? Name and briefly describe at least 5 methods of contraception.
Contraception is the prevention of fertilization and pregnancy. Various methods available:
1. Barrier methods:
a) Condom (male) - latex sheath worn over penis; prevents sperm entry; also prevents STDs
b) Diaphragm (female) - covers cervix; blocks sperm entry; must be used with spermicide
c) Cervical cap - smaller than diaphragm; covers cervix
- Effectiveness: 85-98% with proper use
2. Hormonal methods:
a) Oral contraceptive pills - contain estrogen and progesterone; inhibit FSH and LH; prevent ovulation
b) Intrauterine Device (IUD) - copper or hormone-releasing device placed in uterus; prevents fertilization and implantation
c) Contraceptive patch - releases hormones through skin
d) Contraceptive injection - hormonal injection every 3 months
- Effectiveness: >99% with perfect use
3. Surgical methods:
a) Vasectomy (male sterilization) - cutting of vas deferens prevents sperm release
b) Tubal ligation (female sterilization) - cutting or blocking of fallopian tubes prevents egg passage
- Permanent methods; >99% effective
4. Natural methods:
a) Abstinence - avoiding intercourse during fertile days (ovulation)
b) Coitus interruptus (withdrawal) - removing penis before ejaculation
- Effectiveness: 70-80%
5. Emergency contraception:
- Morning-after pill - high dose of hormones taken within 72 hours of unprotected intercourse
- Effectiveness: 75-89%
Choose based on effectiveness, side effects, and personal preference. Condoms recommended for STD prevention even with other methods.
Q8. What is the menstrual cycle? Describe the four phases and the hormonal changes that occur.
The menstrual cycle is the monthly process in females (13-50 years) involving ovulation and preparation of uterus for pregnancy. Average cycle: 28 days.
Four phases:
1. Menstruation (days 1-5):
- Endometrium of uterus sheds
- Bleeding lasts 3-7 days
- About 30-40 mL blood lost
- Hormones: FSH begins to rise; estrogen and progesterone low
2. Follicular phase (days 1-13):
- FSH rises, stimulating follicles in ovary
- Follicles develop and produce estrogen
- Estrogen causes endometrium to thicken
- Estrogen rises gradually, then surge triggers ovulation
- Hormones: FSH high, estrogen rising
3. Ovulation (around day 14):
- Surge of LH (Luteinizing Hormone) triggers ovulation
- Ovary releases mature egg
- Egg travels into fallopian tube
- Most fertile day of cycle
- Hormones: LH surge very high
4. Luteal phase (days 15-28):
- Remnant of follicle becomes corpus luteum
- Corpus luteum produces progesterone and estrogen
- Progesterone maintains thickened endometrium
- If egg not fertilized, corpus luteum degenerates
- Progesterone and estrogen drop, triggering menstruation
- Hormones: Progesterone high, then drops
If fertilization occurs:
- Zygote produces hCG (human chorionic gonadotropin)
- hCG keeps corpus luteum active
- Endometrium remains thick, pregnancy continues
Regulation: FSH and LH from pituitary; estrogen and progesterone from ovaries and corpus luteum in negative feedback loop
How Do Organisms Reproduce — Practice MCQs with Answers
Attempt these 20 multiple-choice questions after working through the solutions above. Each carries the correct option and the reasoning behind it, so a wrong answer tells you which idea to revisit.
MCQ 1. Which of the following organisms reproduces by binary fission?
- A. Hydra
- B. Spirogyra
- C. Amoeba
- D. Rhizopus
Answer: C. Amoeba — Binary fission is a type of asexual reproduction where a single parent cell divides into two equal daughter cells, as commonly observed in Amoeba.
MCQ 2. The technique used to grow many plants from a small piece of plant tissue or cells in a nutrient medium is called:
- A. Grafting
- B. Layering
- C. Budding
- D. Tissue Culture
Answer: D. Tissue Culture — Tissue culture is an advanced vegetative propagation technique that allows for the rapid production of many plants (plantlets) from a small explant in a sterile, nutrient-rich medium.
MCQ 3. After fertilization in a flower, which part typically develops into the fruit and which develops into the seed?
- A. Ovary into fruit, ovule into seed
- B. Ovule into fruit, ovary into seed
- C. Petal into fruit, sepal into seed
- D. Stamen into fruit, stigma into seed
Answer: A. Ovary into fruit, ovule into seed — Following fertilization, the ovary of the flower matures into the fruit, which encloses the seeds, while the ovules inside the ovary develop into the seeds.
MCQ 4. Where are sperm produced in the human male reproductive system?
- A. Vas deferens
- B. Urethra
- C. Testes
- D. Prostate gland
Answer: C. Testes — The testes are the primary male reproductive organs responsible for producing sperm cells and the male hormone testosterone.
MCQ 5. Fertilization in humans typically takes place in which part of the female reproductive system?
- A. Uterus
- B. Ovary
- C. Vagina
- D. Fallopian tube
Answer: D. Fallopian tube — Fertilization, the fusion of sperm and egg, usually occurs in the fallopian tube (oviduct) after the egg is released from the ovary.
MCQ 6. Which of the following organisms reproduces by forming spores?
- A. Yeast
- B. Hydra
- C. Rhizopus
- D. Planaria
Answer: C. Rhizopus — Rhizopus, a type of fungus, reproduces asexually by forming spores that are enclosed in sporangia and dispersed by air.
MCQ 7. An organism capable of regenerating its entire body from a cut part is:
- A. Amoeba
- B. Hydra
- C. Plasmodium
- D. Leishmania
Answer: B. Hydra — Hydra exhibits true regeneration, where a small cut piece of its body can develop into a complete new individual, provided it contains a part of the nerve net.
MCQ 8. Which event typically marks the end of the reproductive phase in human females?
- A. Puberty
- B. Menstruation
- C. Ovulation
- D. Menopause
Answer: D. Menopause — Menopause is the natural biological process that marks the permanent cessation of menstruation and the end of a woman's reproductive years.
MCQ 9. The male reproductive part of a flower is called the:
- A. Pistil
- B. Carpel
- C. Stamen
- D. Sepal
Answer: C. Stamen — The stamen is the male reproductive organ of a flower, consisting of an anther (producing pollen) and a filament.
MCQ 10. Which of the following is a barrier method of contraception?
- A. Oral pills
- B. Vasectomy
- C. Condom
- D. IUD
Answer: C. Condom — Condoms are barrier methods of contraception that prevent sperm from reaching the egg by physically blocking their passage during sexual intercourse.
MCQ 11. What is the primary function of the placenta during human pregnancy?
- A. Produces eggs
- B. Stores sperm
- C. Provides nutrients and oxygen to the embryo and removes waste
- D. Protects the embryo from physical shocks only
Answer: C. Provides nutrients and oxygen to the embryo and removes waste — The placenta is a vital organ that forms during pregnancy, facilitating the exchange of nutrients, oxygen, and waste products between the mother and the developing embryo/fetus.
MCQ 12. Which organism reproduces by budding?
- A. Spirogyra
- B. Yeast
- C. Planaria
- D. Plasmodium
Answer: B. Yeast — Yeast, a single-celled fungus, reproduces asexually through budding, where a small outgrowth or bud detaches from the parent cell and grows into a new individual.
MCQ 13. An advantage of vegetative propagation is that it allows for the production of:
- A. Genetically diverse offspring
- B. Plants with desirable traits identical to the parent
- C. Plants that produce seeds
- D. Hybrid varieties
Answer: B. Plants with desirable traits identical to the parent — Vegetative propagation produces genetically identical offspring (clones) to the parent plant, ensuring that desirable traits are preserved and passed on without variation.
MCQ 14. Leishmania reproduces by binary fission, but unlike Amoeba, it exhibits:
- A. Multiple fission
- B. Random plane of division
- C. Longitudinal binary fission
- D. Transverse binary fission
Answer: C. Longitudinal binary fission — Leishmania exhibits longitudinal binary fission, where the cell divides along a definite orientation relative to its whip-like flagellum, unlike the random plane of division in Amoeba.
MCQ 15. Which of the following is a bacterial Sexually Transmitted Infection (STI)?
- A. HIV/AIDS
- B. Warts
- C. Gonorrhea
- D. Herpes
Answer: C. Gonorrhea — Gonorrhea is a common sexually transmitted infection caused by the bacterium Neisseria gonorrhoeae. HIV/AIDS, Warts, and Herpes are viral STIs.
MCQ 16. What is the function of the cotyledons in a seed?
- A. Develop into the root
- B. Develop into the shoot
- C. Provide stored food for the embryo
- D. Protect the embryo
Answer: C. Provide stored food for the embryo — Cotyledons are embryonic leaves within a seed that store food reserves, providing essential nourishment to the developing embryo during germination.
MCQ 17. Which of the following surgical methods of contraception involves cutting and ligating the vas deferens in males?
- A. Tubectomy
- B. IUD insertion
- C. Vasectomy
- D. Diaphragm fitting
Answer: C. Vasectomy — Vasectomy is a surgical sterilization procedure for males where the vas deferens are cut and sealed to prevent sperm from reaching the urethra.
MCQ 18. The transfer of pollen grains from the anther to the stigma of a flower is called:
- A. Fertilization
- B. Germination
- C. Pollination
- D. Propagation
Answer: C. Pollination — Pollination is the crucial process involving the transfer of pollen from the male anther to the female stigma, enabling fertilization in flowering plants.
MCQ 19. What is formed when a male gamete fuses with a female gamete?
- A. Embryo
- B. Fetus
- C. Zygote
- D. Ovule
Answer: C. Zygote — The fusion of a male gamete (sperm) and a female gamete (egg) results in the formation of a single diploid cell called a zygote, which is the first cell of a new organism.
MCQ 20. Which hormone is primarily responsible for the development of secondary sexual characteristics in human males?
- A. Estrogen
- B. Progesterone
- C. Testosterone
- D. Insulin
Answer: C. Testosterone — Testosterone is the primary male sex hormone, produced mainly in the testes, responsible for the development of male reproductive tissues and secondary sexual characteristics.
How to Use These Solutions
Attempt each question yourself first and only then compare with the worked answer. Marks in the CBSE board exam are awarded for the METHOD as much as the final result, so reproduce the steps rather than memorising the last line. Where a solution states a law, a formula or a definition, learn that wording — examiners look for it.
Related practice for this chapter: chapter MCQs, previous-year questions, revision notes and sample papers.