About This Section

This is a collection of 30+ solved examples covering every topic of Chapter 7 — from why organisms reproduce, through all the asexual modes, sexual reproduction in plants, the human male and female systems, fertilisation and pregnancy, to reproductive health, contraception and STDs. All the NCERT in-text and exercise questions are worked out here too.

Tips for Board Exam Preparation:

  1. Try each question yourself first, then compare with the solution.
  2. Memorise the key definitions and the labelled diagrams (flower, male system, female system).
  3. Match your answer length to the marks.
  4. Also solve the NCERT textbook exercises.

Let's begin!

Example 1: NCERT — Importance of DNA Copying

What is the importance of DNA copying in reproduction?

Solution: DNA carries the information for the body design of an organism. During reproduction, DNA copying ensures that the offspring receive the same body-design information as the parent, so they resemble the parent. The small variations that arise during copying are also the raw material for evolution.

Example 2: NCERT — Variation and the Species

Why is variation beneficial to the species but not necessarily for the individual?

Solution: Variations allow a species to survive when the environment changes (e.g. a rise in temperature, change in water level). Some variants will be suited to the new conditions and survive. But a particular variation may or may not help a single individual — it is only at the level of the whole population that variation ensures survival over time.

Example 3: NCERT — Binary vs Multiple Fission

How does binary fission differ from multiple fission?

Solution:

  • Binary fission: the parent cell splits into two daughter cells (e.g. Amoeba, bacteria).
  • Multiple fission: the parent cell divides into many daughter cells simultaneously (e.g. Plasmodium).

Key difference: number of offspring produced at a time — two vs many.

Example 4: NCERT — Benefit of Reproducing Through Spores

How will an organism be benefited if it reproduces through spores?

Solution: Spores (e.g. in Rhizopus) are:

  1. Produced in large numbers, so many new individuals can form.
  2. Covered by a thick protective wall that keeps them safe under unfavourable conditions until they land on a moist surface and grow.
  3. Light, so they are easily dispersed to new places.

Example 5: NCERT — Why Complex Organisms Can't Regenerate into New Individuals

Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?

Solution: Complex organisms are not a simple collection of cells. Their cells are organised into tissues, organs and organ systems placed at definite positions. Cutting such an organism cannot reorganise a piece into a whole body with all systems correctly placed. Hence complex organisms use specialised reproductive cells and organs instead of regeneration.

Example 6: NCERT — Why Vegetative Propagation is Practised

Why is vegetative propagation practised for growing some types of plants?

Solution: Because it:

  1. Lets plants that have lost the capacity to produce seeds (banana, orange, rose, jasmine) still be grown.
  2. Produces plants that are genetically identical to the parent, keeping desirable characters.
  3. Allows plants to bear flowers and fruits earlier than seed-grown plants.

Example 7: NCERT — Why DNA Copying is Essential

Why is DNA copying an essential part of the process of reproduction?

Solution: DNA carries the information for body design. Copying the DNA ensures that each new cell/offspring gets a complete set of this information, so the offspring can build a body similar to the parent and carry out life processes. Without DNA copying, the offspring would have no blueprint to develop.

Example 8: Asexual vs Sexual Reproduction

Give three differences between asexual and sexual reproduction.

Solution:

Feature Asexual Sexual
Parents One Two
Gametes Not formed Male + female gametes fuse
Variation Little (offspring ~ identical) More variation

Takeaway: Sexual reproduction's big advantage is greater variation.

Example 9: Identify the Mode of Reproduction

Name the mode of asexual reproduction in: (a) Amoeba, (b) Plasmodium, (c) Hydra, (d) Spirogyra, (e) Rhizopus.

Solution: (a) Amoeba → binary fission (b) Plasmodium → multiple fission (c) Hydra → budding (also regeneration) (d) Spirogyra → fragmentation (e) Rhizopus → spore formation

Example 10: NCERT Exercise — Budding Organism

Asexual reproduction takes place through budding in: (a) Amoeba (b) Yeast (c) Plasmodium (d) Leishmania.

Solution: (b) Yeast. Yeast puts out small buds that separate and grow into new individuals. Amoeba shows binary fission, Plasmodium multiple fission, and Leishmania binary fission in a definite orientation.

Example 11: Regeneration vs Reproduction

Is regeneration the same as reproduction? Explain with an example.

Solution: No. In regeneration (e.g. Hydra, Planaria), a body broken into pieces can grow into complete organisms, carried out by specialised cells. But it is not reproduction, because these organisms do not normally depend on being cut up to multiply. Reproduction is a regular, deliberate way of producing offspring.

Example 12: Tissue Culture

What is tissue culture? State one use.

Solution: Tissue culture is a technique in which new plants are grown by taking a small piece of tissue or a few cells from the growing tip of a plant and placing them in an artificial nutrient medium, where they divide to form a callus. The callus is then shifted to a medium with hormones for growth and differentiation, forming plantlets that are planted in soil.

Use: growing many disease-free plants from one parent (common for ornamental plants).

Example 13: NCERT — Pollination vs Fertilisation

How is the process of pollination different from fertilisation?

Solution:

  • Pollination: the transfer of pollen grains from the anther (stamen) to the stigma (pistil). No fusion of gametes yet.
  • Fertilisation: the fusion of the male germ-cell (from the pollen) with the female gamete (egg in the ovule), forming a zygote.

Order: pollination first, then fertilisation.

Example 14: Self vs Cross Pollination

Distinguish between self-pollination and cross-pollination.

Solution:

  • Self-pollination: pollen is transferred to the stigma of the same flower.
  • Cross-pollination: pollen is transferred from one flower to another (often a different plant), usually with the help of agents like wind, water or animals.

Example 15: Parts of a Flower

Name the four main whorls of a flower and state which are reproductive.

Solution: The four whorls are:

  1. Sepals (calyx) — protective, non-reproductive.
  2. Petals (corolla) — attract pollinators, non-reproductive.
  3. Stamens (androecium) — male reproductive part; produce pollen.
  4. Pistil/Carpel (gynoecium) — female reproductive part; contains ovules.

The stamens and pistil are the reproductive parts.

Example 16: Parts of the Pistil

Name the three parts of the pistil and state what the ovary contains.

Solution: The pistil has:

  1. Stigma — the terminal, often sticky part that receives pollen.
  2. Style — the middle elongated part.
  3. Ovary — the swollen basal part.

The ovary contains ovules, and each ovule has an egg cell.

Example 17: NCERT Exercise — The Anther Contains

The anther contains: (a) sepals (b) ovules (c) pistil (d) pollen grains.

Solution: (d) pollen grains. The anther is the top part of the stamen (male part) and produces the yellowish pollen grains, which contain the male germ-cells.

Example 18: Post-Fertilisation Changes

What happens to the different parts of a flower after fertilisation?

Solution: After fertilisation:

  • The zygote divides to form an embryo within the ovule.
  • The ovule develops a tough coat and becomes the seed.
  • The ovary grows and ripens into the fruit.
  • The petals, sepals, stamens, style and stigma usually shrivel and fall off.

Example 19: Unisexual vs Bisexual Flowers

Differentiate between unisexual and bisexual flowers with examples.

Solution:

  • Unisexual flower: contains either stamens or pistil (not both). Examples: papaya, watermelon.
  • Bisexual flower: contains both stamens and pistil. Examples: Hibiscus, mustard.

Example 20: The Pollen Tube

After pollination, how does the male germ-cell reach the egg?

Solution: After the pollen lands on a suitable stigma, a pollen tube grows out of the pollen grain. This tube travels down through the style to reach the ovary, delivering the male germ-cell to the female gamete inside the ovule, where fertilisation occurs.

Example 21: NCERT — Functions of the Testis

What are the functions performed by the testis in human beings?

Solution: The testes:

  1. Produce sperms (male germ-cells).
  2. Secrete the hormone testosterone, which regulates sperm formation and causes male secondary sexual characters at puberty.

Example 22: Why the Scrotum is Outside the Body

Why are the testes located outside the body in the scrotum?

Solution: Because sperm formation requires a temperature lower than the normal body temperature. The scrotum, being outside the abdominal cavity, provides this cooler environment.

Example 23: NCERT — Seminal Vesicles and Prostate

What is the role of the seminal vesicles and the prostate gland?

Solution: They add secretions to the sperms passing along the vas deferens. This fluid makes sperm transport easier and provides nutrition to the sperms. (Sperms + this fluid = semen.)

Example 24: NCERT Exercise — Not a Female Organ

Which of the following is not a part of the female reproductive system: (a) Ovary (b) Uterus (c) Vas deferens (d) Fallopian tube?

Solution: (c) Vas deferens. The vas deferens is part of the male reproductive system (it carries sperms). Ovary, uterus and fallopian tube are female organs.

Example 25: NCERT — Changes in Girls at Puberty

What are the changes seen in girls at the time of puberty?

Solution:

  1. Increase in breast size with darkening of the nipple skin.
  2. Onset of menstruation.
  3. Growth of hair in armpits and genital region; oily skin (common to both sexes).

Example 26: NCERT — How the Embryo Gets Nourishment

How does the embryo get nourishment inside the mother's body?

Solution: Through the placenta, a disc-shaped tissue embedded in the uterine wall. It has villi on the embryo's side and blood spaces on the mother's side, giving a large surface area. Glucose and oxygen pass from mother to embryo, and wastes pass from embryo to mother.

Example 27: NCERT — Why Menstruation Occurs

Why does menstruation occur?

Solution: Each month the uterus prepares a thick, spongy, blood-rich lining to receive a fertilised egg. If the egg is not fertilised, this lining is not needed and breaks down, leaving the body through the vagina as blood and mucus — this is menstruation. It lasts about 2–8 days.

Example 28: NCERT — Copper-T and STDs

If a woman is using a copper-T, will it help in protecting her from sexually transmitted diseases?

Solution: No. A copper-T is an intra-uterine device that only prevents pregnancy. It is not a barrier, so it does not protect against sexually transmitted diseases. Only barrier methods (condoms) do that.

Example 29: NCERT — Methods of Contraception

What are the different methods of contraception?

Solution:

  1. Barrier methods — condoms, vaginal coverings (also prevent STDs).
  2. Hormonal methods — oral pills (stop egg release).
  3. Intra-uterine devices — loop, copper-T.
  4. Surgical methods — vasectomy (block vas deferens), tubectomy (block fallopian tube).

Example 30: NCERT Exercise — Advantages of Sexual Reproduction

What are the advantages of sexual reproduction over asexual reproduction?

Solution:

  1. It combines DNA from two parents, creating more variation in the offspring.
  2. This variation improves the chances of survival of the species when conditions change.
  3. Variation is the basis for evolution over generations.

Example 31: NCERT Exercise — Modes in Unicellular vs Multicellular Organisms

How are the modes for reproduction different in unicellular and multicellular organisms?

Solution:

  • Unicellular organisms reproduce by simple methods where the whole cell divides — e.g. binary fission (Amoeba), multiple fission (Plasmodium), budding (yeast).
  • Multicellular organisms, having specialised tissues and organs, use more complex methods involving specific reproductive cells/organs — e.g. spore formation, vegetative propagation, or sexual reproduction.

Example 32: NCERT Exercise — Reproduction and Stability of Populations

How does reproduction help in providing stability to populations of species?

Solution: Reproduction produces new individuals to replace those that die, keeping the population size stable. Consistent DNA copying maintains the body-design features that let a species occupy its niche, while the variations generated help the species survive environmental changes. Thus reproduction links directly to the stability of populations over time.

Example 33: NCERT Exercise — Reasons for Contraception

What could be the reasons for adopting contraceptive methods?

Solution:

  1. To avoid unwanted pregnancy and protect the woman's health.
  2. To help control the size of the human population.
  3. To prevent the spread of STDs (with barrier methods like condoms).