CBSE – 10th Standard Science

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Class 10 Chapter 8 – How do Organisms Reproduce?

How do Organisms Reproduce?

  • Reproduction, unlike other life processes, is not essential to maintain the life of an individual organism.
  • Reproduction involves creation of a DNA copy and additional cellular apparatus by the cell involved in the process.
  • Various organisms use different modes of reproduction depending on their body design.

MODES OF REPRODUCTION USED BY UNICELLULAR ORGANISMS

Fission

In fission, many bacteria and protozoa simply divide into two or more daughter

cells.Organisms such as hydra can regenerate if they are broken into pieces. They can also give out buds which mature into new individuals.

Roots, stems and leaves of some plants develop into new plants through vegetative propagation.

These are examples of asexual reproduction where new generations are created from a single individual

Fragmentation

Spirogyra, for example,simply breaks up into smaller pieces upon maturation. These pieces or fragments grow into new individuals.

Regeneration

Many fully differentiated organisms have the ability to give rise to new individual organisms from their body parts. That is, if the individual is somehow cut or broken up into many pieces, many of these pieces grow into separate individuals. For example, simple animals like Hydra and Planaria can be cut into any number of pieces and each piece grows into a complete organism. This is known as regeneration.

Budding and Spore formation

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Vegetative propagation

Some plants produce new plants from a vegetative part like stem, leaves and roots. The resulting plants are clones of parent plant.e.g. potato,onion

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SEXUAL REPRODUCTION

Sexual reproduction involves two individuals for the creation of a new individual.

  • DNA copying mechanisms creates variations which are useful for ensuring the survival of the species.       Modes of sexual reproduction allow for greater variation to be generated.
  • Reproduction in flowering plants involves transfer of pollen grains from the anther to the stigma which is referred to as pollination. This is followed by fertilisation.

Sexual Reproduction in Flowering Plants

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Reproduction in Human Beings

  • Changes in the body at puberty, such as increase in breast size in girls and new facial hair growth in boys, are signs of sexual maturation.
  • The male reproductive system in human beings consists of testes which produce sperms, vas deferens, seminal vesicles, prostate gland, urethra and penis.
  • The female reproductive system in human beings consists of ovaries, fallopian tubes, uterus and vagina.
  • Sexual reproduction in human beings involves the introduction of sperm in the vagina of the female. Fertilisation occurs in the fallopian tube.

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Male Reproductive System

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Female Reproductive System

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