Reproduction in organisms

• Reproduction is essential

  1. For multiplication and maintaining indentity of a species;
  2. To maintain variation among the individual of a species;
  3. To maintain and to inherit genetic constitution or genetic makeup
• Period from birth to natural death is called life span
• Life span is not related with size and complexity of an organism
• Asexual reproduction involves only one parent
• Sexual reproduction involves two parents (male & female)
• In sexual reproduction, offspring are genetically different from their parents
• In asexual reproduction, offspring are identical to their parents
• No organism is immortal except single cell organisms
• Single celled organisms are immortal because no part is left to die. All parts are replaced by new cells
• Life span of

  Elephant - 60-90 years

  Rose- 5-7 years

  Rice - 3-4 months

  Banyan- 200-300 years

  Peepal tree - 2500 years

  Dogs- 25-30 years

  Butterfly - 1-2 weeks

  Crow- 15 years

  Parrot- 140 years

  Banana tree- 25 years

  Cow- 20-25 years

  Crocodile- 60 years

  Horse- 3-4 month

  Fruit fly- 2 weeks

  Tortoise- 100-150 years
• Reproduction is the ability to give birth to new individuals/ offspring of its own kind.
• Reproduction is responsible for continuity of species from generation to generation.
• Reproduction give rise to genetic variation.
• Modes of reproduction depends on

  1. Habitat
  2. Internal physiology
• Asexual mode of reproduction involves only one parent, while sexual mode of reproduction requires two parents.
• In asexual mode of reproduction, there are no gametes involved, whereas in sexual mode of reproduction, gametes (egg cells or sperm) play an important role.
• Types of reproduction

  1. Asexual reproduction or apomixis or somatogenic reproduction
  2. Sexual reproduction or amphimixis or germinal reproduction
• Genetically and morphologically similar individual is called clones
• Asexual reproduction is common in lower organism or organism with simpler organisation and also in some plants by vegetative propagation
• Types of asexual reproduction

  1. Fission
  2. Fragmentation
  3. Budding
  4. Regeneration
  5. Spore formation
  6. Vegetative propagation
• Fission:

  1. Binary fission: Binary fission, asexual reproduction by a separation of the body into two new bodies. Parents cells get divide into two daughter cells. Equal cytokinesis. Parent cell disappear. Bud/ outgrowth/ protuberance is absent

  For example: amoeba

  Types of binary fission:

  1. Irregular fission: example - amoeba
  2. Longitudinal fission: example - euglena
  3. Transverse fission: example - bacteria, paramecium, diatoms
• Karyokinesis: Division of cell nucleus during mitosis

  Cytokinesis: Division of cytoplasm
• Budding:

  Budding is an asexual reproduction method in which a new organism develops from a bud of an existing organism. Bud is also called as outgrowth or protuberance.

  • Unequal cytokinesis
  • Parent cell do not disappear
  • Bud/ outgrowth/ protuberance is present.
• Fragmentation:

  Fragmentation is a type of asexual reproduction in which a whole organism breaks into fragments and each fragment develops into a new individual.

  For example:

  • spirogyra ( filamentous algae),
  • Filamentous fungi
  • Protunemma of mosses ( gametophytes)