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CBSE Class 10 Science Chapter 8 Revision Notes

Asexual and sexual reproduction are two ways that organisms reproduce. The fusion of male and female gametes is not required for asexual reproduction. This occurs in bacteria, amoeba, hydra, and other organisms. In humans and many animals, sexual reproduction includes the union of male and female gametes.

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Chapter 8: How do Organisms Reproduce Revision Notes

Reproduction is the process by which all creatures expand their population by multiplying in number.


  • Asexual reproduction is a type of reproduction in which only one organism reproduces.
  • On its own, a single creature may replicate two or more organisms.
  • All unicellular species, several multicellular organisms, and a few plants have this trait.


  • Fission is a type of asexual reproduction seen in most unicellular organisms.
  • Binary fission occurs when the fission produces two daughter cells (e.g. paramecium).
  • Multiple fission occurs when fission produces a large number of daughter cells (e.g. Plasmodium).
  • Distinct organisms may have different fission planes.


  • Budding is an asexual reproduction method in which a tiny cyst-like formation forms on the parent's body, resulting in the birth of a new person.
  • Buds can stay tied to their parents (yeast) or they can detach and become their own person (hydra).

Fragmentation and regeneration

  • Regeneration is the process through which the organism regrows a lost organ or bodily component (e.g. lizard).
  • Fragmentation is the process of breaking down an organism into smaller parts, each of which develops into a new organism. Planaria, Hydra, etc.

Formation of spores

  • Fungi, for example, produce spores that can be disseminated from their fruiting body and develop into new individuals.

Vegetative propagation

  • In plants, this is a sort of asexual reproduction.
  • The plant's vegetative parts, such as leaves, stems, and roots, produce new plants.
  • Artificial or natural vegetative propagation is possible.
  • Leaves (e.g. bryophyllum), stems (e.g. turmeric, ginger), runners/stolons (e.g. grass runners, strawberry), bulbs (e.g. onion, lily), and so on are all examples of natural vegetative propagation.
  • Cutting, grafting, layering, and plant tissue culture are examples of artificial procedures.


Cell Division Types

In eukaryotic organisms, there are two forms of cell division:

1) Mitosis

  • It is a kind of cell division.
  • It occurs in somatic cells.
  • Maintains the number of chromosomes.
  • Two diploid daughter cells are produced.
  • Asexual reproduction, development, and growth, as well as cell replacement and regeneration, are all dependent on it.

**2) Meiosis **

  • It occurs in sex cells.
  • The number of chromosomes is cut in half.
  • Four haploid daughter cells are produced.
  • Gamete creation is required for sexual reproduction.

Male reproductive system

  • A pair of testes is a male's primary reproductive organ.
  • They generate sperm, which are male sex cells, as well as testosterone, a male sex hormone.
  • Organs of male reproduction
  • A pair of testes is a male's primary reproductive organ.
  • Outside the body, they are found in scrotal sacs and include seminiferous tubules as the structural and functional unit.
  • Seminiferous tubules create male sex cells, sperms, which develop in the epididymis.
  • The hormone testosterone is secreted by Leydig cells, which are found between the seminiferous tubules.
  • Male reproductive organs (accessory reproductive organs)
  • Several reproductive organs that help in the process of reproduction.
  • The seminal vesicles and the prostate gland are reproductive glands that produce semen and nurture sperm.
  • The copulatory organ is the penis with the urethra going through it.

Male reproductive system Source:

Male Ducts

  • The vas deferens and the urethra are the major ducts in men.
  • The vas deferens transports sperm from each testis to the urethra in a single tube.
  • The urethra serves as a conduit for both sperm and urine.

Female reproductive system

  • A pair of ovaries, a pair of fallopian tubes/oviducts, and accessory organs like the uterus and vagina make up the female reproductive system.
  • The female reproductive organ is the most important organ.
  • A female's major reproductive organ is a pair of ovaries.
  • They make female sex cells known as eggs or ova, as well as female sex hormones known as oestrogen and progesterone.

Female accessory reproductive organ

  • In females, the uterus and vagina are accessory reproductive organs.
  • The uterus is where the foetus develops, whereas the vaginal canal gets sperm from the male.



  • When fertilisation does not occur, menstruation is the cyclic process of the ovum being released from the ovary and being removed from the body.
  • The blood-rich endometrium of the uterus also breaks down during menstruation when the ovum is expelled from the body.
  • LH and FSH, two pituitary hormones, and oestrogen and progesterone, two ovarian hormones, all have a role in menstruation.
  • The cycle in humans repeats every 28 days.


Sexual reproduction in flowering plants

  • Flowers are used by plants to reproduce sexually.
  • Flowers with essential whorls, such as androecium and gynoecium, aid in plant sexual reproduction.

Flowers' non-essential components

  • There are necessary whorls and non-essential whorls in the typical floral structure.
  • Because they do not actively participate in reproduction, Sepals and Petals are referred to as non-essential whorls.
  • When in bud condition, sepals shield the inner fragile whorl and, if green in colour, also perform photosynthesis.
  • When petals are coloured, they attract pollinating insects.

Flowers' essential whorls

Reproduction in plants Source:

  • The essential/reproductive whorls of a flower are referred to as androecium and gynoecium.
  • Androecium generates male gametes in pollen grains, whereas gynoecium produces female gametes in ovules.
  • Bisexual flowers have both whorls, whereas unisexual blooms have only one.
  • A stamen is a single androecium component that consists of an anther and filament.
  • Pollen grains produced by the anther are haploid.
  • The stigma, style, and ovary make up each unique gynoecium component, which is referred to as a pistil.


  • Pollination is the process of pollen grains being transferred from anthers to the stigma of a flower.
  • It is required for fertilisation.
  • Self-pollination (autogamy) and cross-pollination are the two forms of pollination (allogamy).
  • Pollen grains are transferred from anthers to the stigma of the same flower or another bloom of the same plant in self-pollination.
  • Pollen is transmitted from anthers to the stigma of another flower in cross-pollination.
  • Cross-pollination is accomplished by a variety of pollinating agents. Water, wind, insects, birds, bats, and other natural phenomena are examples.


  • Fertilization is the fusion of male and female gametes.
  • Pollens germinate on the stigma surface of the pistil in blooming plants following pollination and produce two male nuclei.
  • Ovules have two polar nuclei and an egg cell.
  • Triploid endosperm is formed when one male nucleus unites with two polar nuclei.
  • Another male nucleus joins the egg cell to create the zygote, which produces the embryo and future plant.
  • The ovary forms a fruit after fertilisation, and the ovules become seeds. The rest of the body wilts away.