Reproduction How Life Continues — Class 9 Science NCERT Solutions (Free)
Free step-by-step NCERT solutions for Class 9 Science chapter "Reproduction How Life Continues" — 8 important questions with detailed answers for CBSE board exam preparation.
TL;DR: Free step-by-step NCERT solutions for Class 9 Science chapter "Reproduction How Life Continues" — 8 important questions with detailed answers for CBSE…
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NCERT Solutions for Class 9 Science — Reproduction How Life Continues. Step-by-step answers to all 8 textbook questions from this chapter, written for CBSE board preparation and free to use.
Reproduction How Life Continues — All 8 Questions Solved
Q1. What is reproduction? Distinguish between asexual and sexual reproduction.
Reproduction = Process by which organisms produce offspring and ensure continuation of species.
Asexual reproduction:
• Only one parent involved
• Offspring genetically identical to parent (clones)
• No fusion of gametes
• Examples: Fission, budding, fragmentation, regeneration, vegetative propagation
Sexual reproduction:
• Two parents (male and female) involved
• Offspring genetically different from parents (genetic variation)
• Fusion of male and female gametes (fertilization)
• Produces genetic diversity
• Examples: Most plants and animals
Q2. Explain binary fission with example.
Binary fission = Asexual reproduction where organism divides into two identical daughter cells.
Process: (1) DNA replicates
(2) Replicated chromosomes move to opposite poles
(3) Cell divides into two daughter cells
(4) Each daughter cell contains identical DNA (clones)
Characteristics: (1) No mitotic spindle formation
(2) No membrane-bound nucleus involved
(3) Rapid process, no fusion of gametes
Examples:
• Bacteria (E. coli)
• Amoeba (protozoan)
• Some algae
Q3. Explain budding and regeneration as asexual reproduction.
Budding = Small outgrowth (bud) develops on parent organism; bud detaches and becomes new individual.
Process: (1) Small bud forms on parent body
(2) Bud grows and develops
(3) Bud detaches from parent
(4) New organism grows from bud (genetically identical to parent)
Examples: Hydra, Yeast
Regeneration = Ability to regrow lost body parts; used by some organisms for reproduction (asexual).
Process: (1) Organism loses body part
(2) Remaining part grows back missing portion
(3) May produce new individual from fragment
Examples: Starfish, Flatworm (planaria), Hydra
In some cases (starfish), lost arm regenerates into new individual
Q4. Define vegetative propagation and give four examples.
Vegetative propagation = Asexual reproduction in plants using vegetative parts (stem, leaf, root) not seeds.
No gamete fusion; offspring genetically identical to parent (clones).
Examples:
(1) Fragmentation: Strawberry produces runners that detach and grow (rhizopus fungus)
(2) Bulbs: Garlic, onion bulbs separate and grow independently
(3) Tubers: Potato, yam pieces with buds grow new plants
(4) Layering: Stem bends, touches soil, roots form, detaches as new plant
Other examples: Leaf cuttings (bryophyllum), stem cuttings (rose, sugarcane)
Advantages: (1) Faster than sexual reproduction
(2) Offspring identical to parent (desirable traits preserved)
(3) No variation
Q5. Explain sexual reproduction and its advantages over asexual reproduction.
Sexual reproduction = Reproduction involving fusion of male (sperm) and female (egg) gametes.
Process: (1) Male and female gametes produced (meiosis)
(2) Gamete fusion (fertilization)
(3) Diploid zygote forms
(4) Development into new organism
Advantages:
(1) Genetic variation in offspring (different traits) → Adaptation to environment
(2) Healthy population with diverse traits
(3) Mutation and recombination create new allele combinations
(4) Survival advantage in changing environment
(5) Increases population diversity
Disadvantage: Takes more time and energy; two parents required
Q6. Explain the concept of regeneration in Hydra.
Hydra = Freshwater cnidarian with high regeneration ability.
Regeneration process:
(1) If Hydra is cut into pieces, each piece regenerates missing parts
(2) Cells at cut end dedifferentiate and form blastema (mass of undifferentiated cells)
(3) Blastema cells redifferentiate to form required body parts
(4) Each piece grows into complete new Hydra
Example: If Hydra is cut horizontally:
• Anterior piece regenerates tentacles and mouth
• Posterior piece regenerates foot for attachment
Asexual reproduction: Hydra can also reproduce by budding (small bud forms on parent body)
Significance: Hydra is ideal model organism for studying regeneration and cell differentiation
Q7. What are the differences between fragmentation and regeneration?
Fragmentation:
(1) Parent body deliberately breaks into fragments
(2) Each fragment grows into new individual
(3) Controlled process; all fragments viable
(4) Example: Filamentous algae breaks into fragments; each grows new filament
Regeneration:
(1) Organism loses body part through injury/damage
(2) Missing part regrows from remaining body
(3) May produce new individual if enough remains
(4) Uncontrolled process; depends on extent of injury
Both are asexual reproduction (no gamete fusion; offspring genetically identical to parent).
Similarity: Both produce new organisms from existing cells without sexual fusion
Q8. List and explain four modes of asexual reproduction with one example each.
Four modes of asexual reproduction:
(1) Binary/Multiple fission: Cell divides into identical daughter cells
Example: Amoeba divides into 2 amoebae
(2) Budding: Small outgrowth develops and detaches
Example: Hydra produces bud that detaches into new Hydra
(3) Fragmentation: Body breaks into fragments; each grows into new organism
Example: Starfish arm breaks off and regenerates into new starfish
(4) Vegetative propagation: Uses vegetative parts (stem, root, leaf)
Example: Potato tuber grows new potato plant
All produce genetically identical offspring (clones); no gamete fusion
Reproduction How Life Continues — 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. What is the primary purpose of reproduction in living organisms?
- A. To consume food
- B. To remove waste products
- C. To ensure the continuation of their species
- D. To move from one place to another
Answer: C. To ensure the continuation of their species — Reproduction is a biological process by which new individual organisms – 'offspring' – are produced from their 'parents'. It ensures the survival and continuation of a species.
MCQ 2. Which of the following organisms primarily reproduces through binary fission?
- A. Yeast
- B. Hydra
- C. Amoeba
- D. Spirogyra
Answer: C. Amoeba — Binary fission is a type of asexual reproduction where a single parent cell divides into two identical daughter cells. Amoeba is a classic example of an organism that reproduces through binary fission.
MCQ 3. Budding is a method of asexual reproduction where a small outgrowth develops from the parent body and detaches to form a new individual. Which organism exhibits this mode of reproduction?
- A. Plasmodium
- B. Planaria
- C. Yeast
- D. Rhizopus
Answer: C. Yeast — Yeast and Hydra reproduce by budding. A small bud grows on the parent organism and eventually detaches to become a new, independent organism.
MCQ 4. Fungi like Rhizopus reproduce by forming tiny, light structures that are covered by thick walls to protect them until they come into contact with a moist surface. What are these structures called?
- A. Spores
- B. Buds
- C. Cysts
- D. Gametes
Answer: A. Spores — Rhizopus (bread mould) reproduces asexually through spore formation. Spores are reproductive units capable of developing into new individuals.
MCQ 5. Planaria possesses a remarkable ability to regenerate lost body parts, and if its body is cut into several pieces, each piece can develop into a complete new individual. This process is known as:
- A. Fragmentation
- B. Budding
- C. Regeneration
- D. Spore formation
Answer: C. Regeneration — Regeneration is the process by which an organism regrows lost or damaged body parts, or even develops into a complete new organism from a small fragment, as seen in Planaria.
MCQ 6. Which part of a potato plant is commonly used for vegetative propagation?
- A. Flower
- B. Seed
- C. Tuber (stem)
- D. Root
Answer: C. Tuber (stem) — Potatoes reproduce vegetatively through tubers, which are modified underground stems containing 'eyes' (buds) that can sprout into new plants.
MCQ 7. Which of the following is the male reproductive part of a flower?
- A. Carpel
- B. Stamen
- C. Petal
- D. Sepal
Answer: B. Stamen — The stamen is the male reproductive organ of a flower, consisting of an anther (which produces pollen) and a filament.
MCQ 8. The stigma, style, and ovary collectively form which part of a flower?
- A. Stamen
- B. Petal
- C. Pistil (Carpel)
- D. Sepal
Answer: C. Pistil (Carpel) — The pistil (also called carpel) is the female reproductive part of a flower, comprising the stigma (receives pollen), style (connects stigma to ovary), and ovary (contains ovules).
MCQ 9. The transfer of pollen grains from the anther to the stigma of a flower is known as:
- A. Fertilization
- B. Germination
- C. Pollination
- D. Dispersal
Answer: C. Pollination — Pollination is the crucial step in the sexual reproduction of flowering plants, where pollen grains are transferred from the anther to the stigma, enabling fertilization.
MCQ 10. During fertilization in flowering plants, the male gamete fuses with the egg cell inside which part of the ovule?
- A. Stigma
- B. Style
- C. Ovary wall
- D. Embryo sac
Answer: D. Embryo sac — In flowering plants, the male gamete, carried by the pollen tube, fuses with the egg cell (female gamete) within the embryo sac, which is located inside the ovule.
MCQ 11. After fertilization in a flower, the ovule develops into a ___________ and the ovary develops into a __________.
- A. Fruit, Seed
- B. Seed, Fruit
- C. Flower, Fruit
- D. Seed, Flower
Answer: B. Seed, Fruit — Post-fertilization, the ovules mature into seeds, and the ovary, which encloses the ovules, develops into the fruit.
MCQ 12. Which organ in the male reproductive system produces sperm?
- A. Prostate gland
- B. Urethra
- C. Testes
- D. Vas deferens
Answer: C. Testes — The testes are the primary male reproductive organs responsible for producing sperm and the male hormone testosterone.
MCQ 13. Which organ in the female reproductive system produces egg cells (ova)?
- A. Uterus
- B. Ovaries
- C. Vagina
- D. Fallopian tube
Answer: B. Ovaries — The ovaries are the primary female reproductive organs that produce egg cells (ova) and female hormones like estrogen and progesterone.
MCQ 14. In humans, where does the fusion of male and female gametes (fertilization) typically take place?
- A. Uterus
- B. Ovary
- C. Vagina
- D. Fallopian tube (Oviduct)
Answer: D. Fallopian tube (Oviduct) — Fertilization, the fusion of sperm and egg, normally occurs in the fallopian tube (oviduct) after the egg is released from the ovary.
MCQ 15. After fertilization, the single-celled zygote divides repeatedly to form a ball of cells that eventually implants in the wall of the uterus. What is this developing structure called immediately after implantation?
- A. Gamete
- B. Foetus
- C. Embryo
- D. Ovum
Answer: C. Embryo — After fertilization, the zygote undergoes cell division to form an embryo. Once implanted in the uterine wall, this developing structure is referred to as an embryo until about the eighth week of pregnancy.
MCQ 16. The placenta is a specialized tissue that develops during pregnancy. What is its primary function?
- A. To produce hormones for childbirth
- B. To protect the foetus from mechanical shock
- C. To provide nutrients and oxygen to the foetus and remove waste products
- D. To facilitate the movement of the foetus within the uterus
Answer: C. To provide nutrients and oxygen to the foetus and remove waste products — The placenta acts as a vital link between the mother and the developing foetus, facilitating the exchange of nutrients, oxygen, and waste products through diffusion.
MCQ 17. Which of the following is generally considered a secondary sexual characteristic in males during puberty?
- A. Growth of testes
- B. Development of sperm
- C. Deepening of voice
- D. Maturation of prostate gland
Answer: C. Deepening of voice — Secondary sexual characteristics are external physical changes that signal sexual maturity. Deepening of voice, growth of facial and body hair are examples in males, distinct from primary characteristics like sperm production.
MCQ 18. What happens if an egg cell released by the ovary is not fertilized in the female reproductive system?
- A. It remains in the fallopian tube indefinitely.
- B. It forms a new embryo without fertilization.
- C. The uterine lining sheds, leading to menstruation.
- D. It gets absorbed back into the ovary.
Answer: C. The uterine lining sheds, leading to menstruation. — If the egg is not fertilized, the thickened and nutrient-rich lining of the uterus is no longer needed to support a potential pregnancy, so it breaks down and is shed, resulting in menstruation.
MCQ 19. Which of the following is an advantage of asexual reproduction?
- A. It leads to greater genetic variation.
- B. It requires two parents, increasing adaptability.
- C. It allows for rapid population growth in stable environments.
- D. It is less susceptible to environmental changes.
Answer: C. It allows for rapid population growth in stable environments. — Asexual reproduction allows organisms to reproduce quickly and efficiently, producing many offspring in a short period, which is advantageous in stable environments where genetic variation is not critical.
MCQ 20. Why is sexual reproduction considered to have an evolutionary advantage over asexual reproduction?
- A. It allows organisms to reproduce faster.
- B. It produces genetically identical offspring.
- C. It leads to genetic variation, enhancing adaptability to changing environments.
- D. It requires less energy expenditure.
Answer: C. It leads to genetic variation, enhancing adaptability to changing environments. — Sexual reproduction involves the fusion of gametes from two parents, leading to genetic recombination and variation in offspring, which increases a species' ability to adapt and survive in changing environments.
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.