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Asexual Reproduction

  • It is a type of reproduction in which only a single individual produces an offspring without the involvement of male and female sex cells
  • This is mostly seen in unicellular organisms but some multicellular organisms including plants also show asexual reproduction. Example Bryophyllum which reproduces by vegetative propagation.

The various types of asexual reproduction are:

Fission 

The word fission refers to division of an entity into two or more parts . Fission is seen in unicellular organisms . In this, simple cell division leads to the formation of new daughter cells. Fission is of 2 types:

Binary Fission: 

‘Binary’ means 2 . As the name suggests, binary fission involves the division of a cell into two daughter cells . Bacteria, Paramoecium , and Leishmania (organism causing kala-azar) show binary fission.

BINARY FISSION IN AMOEBA - Teachoo.jpg

Multiple Fission:

In this type of fission, the parent cell divides to produce more than two daughter cells at the same time . Example malaria causing parasite Plasmodium .

 

MULTIPLE FISSION - Teachoo.jpg

Fragmentation

It is seen in multicellular organisms with relatively simple body design. In fragmentation, the body simply breaks into smaller pieces and these pieces grow and mature into new individuals. Eg. Spirogyra

FRAGMENTATION IN SPIROGYRA - Teachoo.jpg

Note: 

  • Higher multicellular organisms cannot simply grow by cell to cell division because they are not just a random collection of cells.
  • In multicellular organisms, specialised cells are organised into tissues, tissues to organs, organs to organ systems and final into the organism. 
  • Also, different cells perform different functions .Therefore, we need more complex systems for reproduction in these organisms.

Regeneration 

  • The body of some organisms is capable of giving rise to the whole new individual
  • This type of asexual reproduction is known as regeneration. 
  • If the individual is broken into several small pieces, then these pieces will grow into new individuals.

Example Planaria and Hydra

There are special cells that carry out regeneration . These cells proliferate and produce large numbers of cells which undergo certain changes to become various cell types.

REGENERATION IN PLANARIA - Teachoo.jpg

Budding:

In budding, a small outgrowth develops on the body of the organism due to repeated cell division known as bud . When this bud develops into a small individual, it detaches from the parent and becomes a new individual. Eg. Hydra, yeast

BUDDING IN YEAST - Teachoo.jpg

Vegetative Propagation

The ability of plants to give rise to new individuals from their various body parts like roots, stems, leaves etc. is known as vegetative propagation. Example leaves of Bryophyllum show this property.

VEGETATIVE PROPAGATION IN BRYOPHYLLUM - Teachoo.jpg

Layering (in which a branch of a plant is used to produce new individuals) and grafting (in which a stem is capable of producing a new plant) are two such methods that can be used to grow sugarcane, rose, grapes etc.

LAYERING - Teachoo.jpg

GRAFTING - Teachoo.jpg

Advantages of vegetative propagation:

  • The new plants can be grown much faster by using this method as compared to those grown from seed.
  • Plants like banana, rose, orange and jasmine which have lost their ability to produce seeds can be grown by vegetative propagation .
  •  Also, all the plants produced are genetically similar to the parent and have all its characteristics.

Spore Formation 

  • Spores are the microscopic reproductive units
  • In this type of reproduction, the parent produces a large number of these tiny spores into the environment and these spores germinate to form a new plant in favourable conditions like damp and warm environment with abundant food upon coming in contact with land/soil. 
  • Spore formation is mostly seen by fungi like rhizopus, mucor etc.

 

SPORE FORMATION IN RHIZOPUS - Teachoo.jpg

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Transcript

BINARY FISSION IN AMOEBA Parent Cell Nucleus Divides Cytoplasm Divides Two Daughter Cells FRAGMENTATION IN SPIROGYRA Nucleus Septa Spiral Chloroplast BUDDING IN YEAST Parent Yeast Cell Nucleus Forming of bud Bud with nucleus Cytoplasm Divides Daughter Yeast Chain of yeast cells formed Parent Yeast REDUCTION DIVISION Daughter Nuclei Daughter Nuclei II Interphase Homologous Chromosomes Meiosis I Meiosis II MULTIPLE FISSION Schizont Daughter Nuclei Rupturing schizont wall Merozoites SPORE FORMATION IN RHIZOPUS Sporangium Spores Hypha VEGETATIVE PROPAGATION IN BRYOPHYLLUM Buds LAYERING Parental Plant New Plant Roots GRAFTING Scion Stock Graft union Wrapped & Waxed

CA Maninder Singh's photo - Co-founder, Teachoo

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CA Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 12 years and a teacher from the past 16 years. He teaches Science, Economics, Accounting and English at Teachoo