Asexual reproduction is a process in which new organism is produced from a single parent without the involvement of gametes or sex cells. Many unicellular and multicellular organisms reproduce asexually. In this process, parent organism either splits or a part of parent organism separates to form a new organism. In this reproduction, certain cells of the parent undergo mitotic cell division so that two or more new organisms are formed.
There are six types of asexual reproduction. They are:
3) Spore formation
6) Vegetative propagation
In fission, unicellular organism splits to form new organisms. It is a process of reproduction in organisms such as protozoa and many bacteria. There are two types of fission:
In binary fission, the parent cell divides into two after reaching a point where it has fully grown. In this process, after splitting parent cell do not exist and two new organisms are formed.
Examples of unicellular organisms that undergo binary fission are amoeba, paramecium, Leishmania etc.
Amoeba reproducing by binary fission.
Multiple fission is also a process of asexual reproduction in which parent cell splits to form many new organisms. This happens when cyst is formed around a unicellular organism. Inside this cyst the nucleus of an organism breaks in many smaller nuclei. When the favourable conditions come, the cyst breaks and the many daughter cells inside it are released.
Plasmodium undergoes the process of multiple fission.
Reproduction by multiple fission.
The word bud means small outgrowth. In the process of budding, a small bud grows on the body of parent organism and when the time comes it detaches itself to form a new organism. Hydra and yeast undergoes the process of budding.
Hydra reproducing by the method of budding.
Yeast reproducing by the method of budding.
The method of spore formation occurs in both unicellular and multi-cellular organisms. This process takes place in plants. In spore formation, the parent plant produces hundreds of reproductive units called spores in its spore case. When this spore case of the plant bursts, these spores travel in air and land on food or soil. Here they germinate and produce new plants.
Fungi like Rhizopus, Mucor, etc., are examples of spore formation.
This is a common bread mould plant or rhizopus fungus. It reproduces by forming spores.
Regeneration is an asexual method of reproduction. In this process, if the body of a parent organism gets cut, then each cut part can regenerate and form a whole new organism from its body parts. This happens because when the body of an organism that can undergo regeneration gets cut then the cells of cut body part divide rapidly and form a ball of cells. These cells then move to their proper places to form organs and body parts.
Regeneration occurs in both plants and animals. Hydra and planaria undergo regeneration.
Regeneration in Planeria.
Fragmentation occurs in multicellular organisms, be it plants or animals. In this process the multicellular organism breaks into two or more pieces on maturation. Each piece than grows into a new organism. Spirogyra which is a plant and sea anemones which is a sea animal undergoes the process of fragmentation.
Spirogyra, a filament type algae plant reproduces by the method of fragmentation.
This form of asexual reproduction occurs in plants only. In vegetative propagation, parts of old plant like stems, roots and leaves are used to grow a new plant. The buds which are present in dormant state in old plant are provided with suitable conditions like moisture and warmth so that they grow and develop to form a new plant.
Plants that undergo vegetative propagation are green grass, Bryophyllum, money plant, potato plant, onion, banana, etc.
Vegetative propagation of potato plant from a Potato tuber. Plantlets growing in the margin of bryophyllum leaf.
Artificial Propagation of Plants
When many plants are grown from one plant using man-made methods, it is called artificial propagation. There are three common methods of artificial propagation of plants. They are:
A new plant is grown by cutting a small part of a plant which can be a stem or a leaf that has a bud on it. This part is then grown into soil and watered. After a few days one can notice a new plant growing.
Plants like bougainvillea, chrysanthemum, grapes, etc., can be grown by cutting.
The propagation of plants by ‘cuttings’ method.
In layering the branches of the parent plant are allowed to go inside the soil in such a way that a part of the branch comes out of the soil. The part of the branch which is inside the soil develops roots and is later cut from the parent plant. In this way a new plant is formed from the buried branch.
The layering method is used for the plants like Jasmine, Strawberry, raspberry, etc.
The propagation of Jasmine plant (Chameli) by the layering method.
In grafting stems of two different plants is cut and joined in such a way that they grow as on plant. Of the two cut stems, one stem is with the roots and is called stock. The other stem is cut without roots and is called scion. Stock is the lower part of the plant and scion is the upper part of the plant. A slanting cut is made in both the stems.
The cut surfaces of scion and stock are fitted and tied together with a piece of cloth and covered with polythene sheet. This protects the stem from infections and other problems.
Soon the stock and scion combine and a new plant grow. The fruits of this new plant have the characteristics of both the plants. Examples of fruit which are grafted are apple, peach, apricot etc.
The grafting method for the artifical propagation of plants or trees.
Advantages of artificial vegetative propagation
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