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16.1) Asexual reproduction

16.1) Asexual reproduction

 

Asexual reproduction: is the process resulting in the production of genetically identical offspring from one parent.

 

Bacteria:

  • Bacteria are tiny single-celled organisms. They reproduce by a process called binary fission.
  • In binary fission, one bacterium grows and exact copy of its DNA coil which carries its genetic information. Then the bacterium completely divides which one DNA coil in the parent and one in the daughter bacterium.
  • Each bacterium can undergo binary fission once every 20 minutes making them able to reproduce massive numbers from one parent in very little time.

 

Fungi:

  • Fungi are multicellular organisms that grow long threads called hyphae on pieces of food.
  • There are two types of hyphae, reproductive and feeding hyphae.
  • Reproductive hyphae grow vertically above the food material. At the top of the hyphae, there is a spherical bag in which many spores are grown.
  • This bag is called sporangium. Spores being produced in the sporangia are reproductive structures that can grow into another fungus. At some point, the sporangium will burst open dispersing the spores into the air. If a spore falls on an area of favorable conditions (food – water – air) it will germinate and grow into a new identical fungus.

 

Runners (stolons) and rhizomes:

  • Some plants naturally produce side branches with plantlets on them.
  • The spider plant does this. Other plants, such as strawberries, produce runners with plantlets on them.
  • Rhizomes grows under the ground

Bulbs:

  • Many plants naturally develop underground food storage organs that later develop into the following year’s plants – potato tubers and daffodil bulbs are examples of this.

 

Artificial cloning in plants:

Cloning plants has many important commercial implications – it allows a successful variety of a plant to be produced cheaply in a short space of time and on a massive scale.

Cuttings:

  • Putting the cut end of a shoot into water or moist earth.
  • Roots grow from the base of the stem into the soil while the shoot continues to grow and produce leaves.

 

Tissue culture:

  • It uses tiny pieces from the parent plant, rather than cuttings.
  • Sterile agar jelly with plant hormones and lots of nutrients are needed.
  • Tissue culture is more expensive and more difficult than taking cuttings.

 

The advantages and disadvantages of asexual reproduction:

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