NCERT Class 10 Science Chapter 7 – How do Organisms Reproduce?

NCERT Class 10 Science Chapter 7 explains the process of reproduction in living organisms. In NCERT Class 10 Science Chapter 7, students learn how organisms produce new individuals, why variation occurs, and how reproduction ensures continuity of species. NCERT Class 10 Science Chapter 7 is an important biology chapter because it builds the foundation for heredity, genetics and evolution.

NCERT Class 10 Science Chapter 7 begins with the idea that organisms do not create exact copies of themselves. During reproduction, DNA copying takes place, and small variations arise. These variations are important for survival and long-term evolution. Understanding this concept in NCERT Class 10 Science Chapter 7 helps students connect reproduction with heredity.

NCERT Class 10 Science Chapter 7 discusses two major modes of reproduction:

Asexual Reproduction – Involves a single parent and produces genetically similar offspring.
Examples covered in NCERT Class 10 Science Chapter 7 include:

• Binary Fission (Amoeba)
• Multiple Fission (Plasmodium)
• Fragmentation (Spirogyra)
• Regeneration (Hydra, Planaria)
• Budding (Yeast)
• Vegetative Propagation (Bryophyllum, Potato)
• Spore Formation (Rhizopus)

Sexual Reproduction – Involves two parents and fusion of Gametes. NCERT Class 10 Science Chapter 7 explains that sexual reproduction increases genetic variation and ensures better adaptability.

In flowering plants, NCERT Class 10 Science Chapter 7 describes reproduction through the Flower, where the Stamen produces pollen grains and the Pistil contains the ovary. Fertilisation leads to formation of a Zygote, which develops into a seed.

In humans, NCERT Class 10 Science Chapter 7 explains the structure and function of the male and female reproductive systems. Fertilisation occurs in the Fallopian Tube, and the embryo develops in the uterus. NCERT Class 10 Science Chapter 7 also highlights menstrual cycle and reproductive health.

NCERT Class 10 Science Chapter 7 is highly important for CBSE board exams and foundation-level competitive exams because it connects reproduction with heredity and genetics.

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7.1 Do organisms create exact copies of themselves?

• Organisms look similar because their Body Design is similar, and this design is controlled by information present in DNA (Deoxyribo Nucleic Acid) located in chromosomes inside the nucleus.
• Reproduction at its basic level involves making copies of the Blueprint of Body Design, which means copying the DNA accurately.
• During reproduction, cells use chemical reactions to create a DNA Copy, resulting in two copies that must be separated into two cells.
• DNA copying is accompanied by formation of additional Cellular Apparatus, after which the cell divides to form two daughter cells.
• DNA copying is not perfectly accurate because no biochemical reaction is absolutely reliable, leading to small Variations in each generation.
• Some variations may be harmful and cause death of the new cell, while others are subtle and allow survival with slight differences.
• Thus, organisms do not create exact copies of themselves; new individuals are Similar but Not Identical, and this inbuilt variation becomes the basis of Evolution.

7.1.1 The Importance of Variation

• Populations of organisms occupy specific Niches in an ecosystem, and accurate DNA copying helps maintain body features suited to that niche.
• Reproduction ensures stability of a species by preserving successful Body Designs across generations.
• Environmental conditions such as Temperature Changes, Water Level Variation or Natural Calamities can alter niches beyond the control of organisms.
• If all individuals were identical, a sudden environmental change could wipe out the entire population.
• Presence of Variations in some individuals increases the chance that a few may survive under changed conditions.
• For example, if water temperature rises, most bacteria may die, but heat-resistant variants can survive and multiply.
• Thus, variation is not always beneficial for an individual, but it is essential for long-term Survival of Species.

7.2 Modes of reproduction used by single organisms

• Many organisms reproduce from a Single Parent, and this method is called Asexual Reproduction.
• In asexual reproduction, new individuals are produced without formation or fusion of Gametes.
• Since only one parent is involved, the offspring are usually Genetically Similar to the parent, with minor variations due to DNA copying errors.
• The mode of reproduction depends on the Body Design and level of organisation of the organism.
• In Unicellular Organisms, cell division itself leads to reproduction.
• In simple Multicellular Organisms, reproduction may occur through body parts or specialised cells.
• Asexual reproduction allows rapid multiplication and production of large numbers of individuals in favourable conditions.

7.2.1 Fission

• In Unicellular Organisms, reproduction occurs through Cell Division, which is called Fission.
• In Binary Fission, a single parent cell divides into two equal daughter cells, as seen in Amoeba and many bacteria.
• In Amoeba, division can occur in any plane, while in Leishmania (which causes kala-azar), division occurs in a definite orientation due to its whip-like structure.
• In Multiple Fission, one parent cell divides into many daughter cells simultaneously, as seen in Plasmodium (malarial parasite).
• During multiple fission, the nucleus divides repeatedly before the cytoplasm separates into several daughter cells.
• Fission enables rapid increase in population under favourable environmental conditions.

7.2.2 Fragmentation

• Fragmentation is a mode of asexual reproduction in which a multicellular organism breaks into two or more fragments, and each fragment grows into a new individual.
• It occurs in organisms with relatively simple body organisation such as Spirogyra, a filamentous green alga.
• When Spirogyra matures, its filament breaks into smaller pieces, and each piece develops into a complete organism.
• Fragmentation is possible because the body is not highly organised into specialised tissues and organs.
• In complex multicellular organisms, fragmentation is not possible since specialised tissues and organs must be arranged in specific positions.
• This method allows rapid multiplication when environmental conditions are favourable.

7.2.3 Regeneration

• Regeneration is the ability of certain organisms to develop a complete individual from body fragments.
• It occurs in simple animals such as Hydra and Planaria, where each cut piece can grow into a new organism.
• Regeneration is carried out by Specialised Cells that divide repeatedly to form a mass of cells.
• These cells then undergo organised changes called Development to form different tissues and organs.
• Regeneration is not the same as reproduction because most organisms do not normally depend on being cut into pieces to reproduce.
• This process is possible only in organisms with relatively simple body organisation and high regenerative capacity.

7.2.4 Budding

• Budding is a form of asexual reproduction in which a new individual develops as an outgrowth from the parent body.
• It occurs in organisms such as Hydra and Yeast.
• In Hydra, a bud forms due to repeated Cell Division at a specific site on the body wall.
• The bud grows into a miniature individual while attached to the parent.
• When fully developed, the bud detaches and becomes an independent organism.
• Budding allows rapid multiplication under favourable conditions.

7.2.5 Vegetative Propagation

• Vegetative Propagation is a type of asexual reproduction in plants where new plants develop from Root, Stem or Leaf under suitable conditions.
• Plants such as Sugarcane, Rose and Grapes are commonly grown using methods like Layering and Grafting.
• In Bryophyllum, buds present on the leaf margins fall on soil and develop into new plants.
• Vegetative propagation enables plants like Banana, Orange, Jasmine and Rose, which have reduced seed-forming capacity, to reproduce.
• Plants produced through vegetative propagation are Genetically Similar to the parent plant and retain all its characteristics.
• This method allows earlier flowering and fruiting compared to plants grown from seeds.
• A modern technique called Tissue Culture involves growing new plants from small pieces of plant tissue in an artificial nutrient medium under controlled conditions.

7.2.6 Spore Formation

• Spore Formation is a method of asexual reproduction in which organisms produce specialised reproductive units called Spores.
• It occurs in organisms such as Rhizopus (bread mould), where spores are formed inside structures called Sporangia.
• The sporangia appear as tiny blob-like structures at the tips of upright hyphae.
• Each spore is covered by a thick protective wall that helps it survive unfavourable environmental conditions.
• When spores come in contact with a moist and suitable surface, they germinate and develop into new individuals.
• Spore formation allows production of a large number of offspring in a short period.
• This method ensures survival and rapid spread of organisms under favourable conditions.

7.3 Sexual reproduction

• Sexual Reproduction involves participation of two individuals, a Male and a Female, for producing a new generation.
• It requires formation and fusion of specialised reproductive cells called Gametes.
• Sexual reproduction leads to combination of DNA from two parents, creating new genetic combinations.
• Unlike asexual reproduction, sexual reproduction increases the chances of Variation in the offspring.
• The fusion of male and female gametes forms a Zygote, which develops into a new organism.
• Specialised reproductive organs and tissues are required for production and transfer of gametes.
• Sexual reproduction is common in most Multicellular Organisms, including plants and human beings.

7.3.1 Why the Sexual Mode of Reproduction?

• DNA copying during reproduction is not perfectly accurate, and small errors generate Variations in a population.
• In asexual reproduction, variations arise slowly because they depend only on errors during DNA Copying.
• Sexual reproduction increases variation by combining DNA from two different individuals, creating new combinations of inherited traits.
• Each parent contributes one set of Chromosomes, preventing doubling of DNA in every generation.
• Specialised cells called Germ Cells (Gametes) contain half the number of chromosomes and are formed by a type of cell division called Meiosis.
• When two gametes fuse, the normal chromosome number is restored in the Zygote, maintaining genetic stability.
• One gamete is usually large and stores food (Female Gamete), while the other is smaller and motile (Male Gamete).
• Thus, sexual reproduction promotes greater Genetic Diversity, which improves chances of survival of species over time.

7.3.2 Sexual Reproduction in Flowering Plants

• In flowering plants (Angiosperms), reproduction takes place in the Flower, which contains male and female reproductive organs.
• The flower may be Unisexual (Papaya, Watermelon) or Bisexual (Hibiscus, Mustard).
• The Stamen is the male reproductive part and produces yellow Pollen Grains, which contain the male gametes.
• The Pistil is the female reproductive part and consists of Stigma, Style and Ovary.
• The Ovary contains Ovules, and each ovule has an Egg Cell (Female Gamete).
• Transfer of pollen from anther to stigma is called Pollination, which may occur by wind, water or insects.
• After pollination, pollen germinates on the stigma and forms a Pollen Tube that carries the male gamete to the ovule.
• Fusion of male and female gametes is called Fertilisation, leading to formation of a Zygote, which develops into a seed and later into a new plant.

7.3.3 Reproduction in Human Beings

• Human beings reproduce sexually and require participation of both Male and Female individuals.
• During Adolescence, the body undergoes changes known as Puberty, when reproductive organs mature and begin producing gametes.
• In boys, changes include growth of facial hair, deepening of voice and enlargement of reproductive organs due to the hormone Testosterone.
• In girls, changes include development of breasts and onset of Menstruation, regulated by female hormones.
• Sexual reproduction involves transfer of Sperms from male to female reproductive system during mating.
• Fertilisation occurs when a sperm fuses with an egg in the Fallopian Tube, forming a Zygote.
• The zygote divides repeatedly and develops into an Embryo, which grows inside the uterus.
• Proper development requires nourishment from the mother and specialised reproductive organs in both sexes.

7.3.3 (a) Male Reproductive System

• The Male Reproductive System consists of organs that produce and transport male gametes called Sperms.
• The Testes are located outside the abdominal cavity in a pouch called the Scrotum, because sperm formation requires a temperature lower than normal body temperature.
• The testes produce Sperms and secrete the hormone Testosterone, which regulates sperm production and brings about changes during puberty.
• Sperms are transported from the testes through the Vas Deferens to the urethra.
• The Seminal Vesicles and Prostate Gland add secretions to sperms to form Semen, which provides nourishment and helps in transport.
• The Urethra passes through the Penis, which becomes erect during sexual act and helps in transfer of semen into the female reproductive system.
• The male reproductive system is specialised for production, nourishment and delivery of male gametes for fertilisation.

7.3.3 (b) Female Reproductive System

• The Female Reproductive System consists of organs that produce female gametes and support development of the embryo.
• The Ovaries produce Eggs (Ova) and secrete female hormones such as Oestrogen and Progesterone.
• Each ovary releases one mature egg approximately once every month in a process called Ovulation.
• The egg is carried from the ovary to the uterus through the Fallopian Tube (Oviduct), where fertilisation normally occurs.
• The Uterus is a muscular organ where the fertilised egg implants and develops into an embryo.
• The inner lining of the uterus, called the Endometrium, thickens every month to receive the fertilised egg.
• The Vagina serves as the passage for entry of sperms and also acts as the birth canal during childbirth.

7.3.3 (c) What happens when the Egg is not Fertilised?

• If the released Egg is not fertilised by a sperm, it does not develop into a zygote.
• The thickened lining of the Uterus (Endometrium), which was prepared to receive a fertilised egg, is no longer required.
• This uterine lining gradually breaks down along with the unfertilised egg.
• The broken tissues and blood are expelled from the body through the vagina in a process called Menstruation.
• Menstruation occurs approximately once every 28 days, though the cycle may vary among individuals.
• The menstrual cycle begins at Puberty and continues until Menopause, marking the end of the reproductive phase in women.

7.3.3 (d) Reproductive Health

• Reproductive Health refers to a state of physical, mental and social well-being in matters related to the reproductive system.
• Awareness about changes during Puberty helps adolescents understand normal body development and avoid misconceptions.
• Methods of Contraception are used to prevent unwanted pregnancy, including Condoms, Oral Pills, Copper-T and Surgical Methods.
• Condoms also help prevent Sexually Transmitted Diseases (STDs) such as HIV/AIDS.
• Proper hygiene during Menstruation is important to prevent infections and maintain health.
• Early marriage and teenage pregnancy can affect health; therefore, awareness and education are essential.
• Access to medical facilities and counselling plays an important role in maintaining reproductive health.

Exam Oriented Facts

• Reproduction is the process by which organisms produce new individuals of their own kind, ensuring continuity of species.
• The basic event in reproduction is DNA Copying, which leads to inheritance of traits from parents to offspring.
• DNA copying is not perfectly accurate, resulting in Variations, which form the basis of Evolution.
• Variation is beneficial for Survival of Species, especially under changing environmental conditions.
• Asexual Reproduction involves a single parent and produces genetically similar offspring.
• Sexual Reproduction involves two parents and increases Genetic Diversity through fusion of gametes.
• Binary Fission occurs in Amoeba (any plane) and Leishmania (definite orientation).
• Multiple Fission occurs in Plasmodium (malarial parasite).
• Fragmentation occurs in Spirogyra, where body fragments grow into new individuals.
• Regeneration is seen in Hydra and Planaria, where body parts develop into complete organisms.
• Budding occurs in Hydra and Yeast through outgrowth formation.
• Vegetative Propagation occurs in plants like Sugarcane, Rose, Grapes, Banana, Jasmine.
• Bryophyllum produces buds on leaf margins.
• Spore Formation occurs in Rhizopus (bread mould) through Sporangia containing spores.
• Sexual reproduction involves formation of Gametes by Meiosis (half chromosome number).
• Fusion of gametes forms a Zygote, restoring normal chromosome number.
• Male gamete is usually small and motile; female gamete is larger and stores food.
• Reproductive part of angiosperms is the Flower.
• Stamen produces Pollen Grains (male gametes).
• Pistil consists of Stigma, Style and Ovary.
• Ovule inside ovary contains the egg cell.
• Pollination is transfer of pollen from anther to stigma.
• Fertilisation is fusion of male and female gametes inside ovule.
• Puberty begins during Adolescence, leading to sexual maturation.
• Male hormone: Testosterone; Female hormones: Oestrogen and Progesterone.
• Testes produce sperms; located in Scrotum (lower temperature required).
• Female system includes Ovaries, Fallopian Tubes, Uterus and Vagina.
• Fertilisation occurs in the Fallopian Tube.
• If egg is not fertilised, Menstruation occurs approximately every 28 days.
• Contraceptive methods include Condoms, Oral Pills, Copper-T and Surgical Methods.
• Condoms help prevent Sexually Transmitted Diseases (STDs).

NCERT Class 10 Science Chapter 7 – How do Organisms Reproduce? is one of the most important biology chapters in Class 10. A clear understanding of NCERT Class 10 Science Chapter 7 helps students build strong conceptual clarity in reproduction, variation and genetic continuity.

NCERT Class 10 Science Chapter 7 directly supports the study of Chapter 8 (Heredity) and strengthens preparation for CBSE board exams and foundation-level competitive exams. Mastering NCERT Class 10 Science Chapter 7 ensures better performance in long-answer and diagram-based questions.

Continue reading NCERT Class 10 Science Chapter 8 – Heredity to deepen your understanding of genetic inheritance.

FAQs

Q1. What is NCERT Class 10 Science Chapter 7 about?
NCERT Class 10 Science Chapter 7 explains reproduction in organisms, including asexual and sexual reproduction, plant reproduction and human reproduction.

Q2. Why is NCERT Class 10 Science Chapter 7 important for exams?
NCERT Class 10 Science Chapter 7 is important because it forms the base for heredity, genetics and evolution, which are frequently asked in CBSE exams.

Q3. What are the two types of reproduction discussed in NCERT Class 10 Science Chapter 7?
NCERT Class 10 Science Chapter 7 explains asexual reproduction and sexual reproduction.

Q4. Where does fertilisation occur according to NCERT Class 10 Science Chapter 7?
According to NCERT Class 10 Science Chapter 7, fertilisation in humans occurs in the fallopian tube.

Q5. How does NCERT Class 10 Science Chapter 7 help in understanding heredity?
NCERT Class 10 Science Chapter 7 explains variation and DNA copying, which directly lead to the concepts of heredity studied in the next chapter.

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