Reproduction in Organisms - Asexual Reproduction

Lifetime or Life Span

That certain state or time of living organism or plant till which it remains alive. is called lifetime. In other words, the period or time period from birth to death of an organism or plant class is called life span.

After the birth of the organism, the activities of growth, development, maturation and reproduction take place, in the end old age comes and the organism dies.

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Reproduction

After the completion of the time period of the living being, the living being dies, but before the death, it produces a living being similar to itself, which maintains the continuity of the progeny of that living being.

Therefore, 'Reproduction is that action of the organism, by which it gives birth to its own organism or progeny.' This progeny maintains the continuity of the living organism's life.

In other words, 'the ability of an organism to produce new offspring similar to itself is called reproduction.' Information flows from one generation to another in the form of genetic material to produce a new organism in reproduction.

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Types Of Reproduction

There are mainly three types of reproduction occur in organisms.

1. Asexual Reproduction
2. Sexual Reproduction
3. Vegetative Reproduction

1 . Asexual Reproduction

In the process of asexual reproduction, new offspring organisms are produced by only one organism. In this, gametes are not produced by gametogenesis. The new progeny organism has all the characteristics from which it originated, that is, there is no disparity between the parent organism and the progeny organism. For this reason, the progeny organism is also called a clone. Inequality in them can come only through mutation.

There are various methods of asexual reproduction, the details of which are as follows –

• Fission
• Fragmentation
• Budding
• Sporulation or Sporogenesis
• Zoospores
• Aplanospores
• Conidia
• Chlamydospores
• Gemmul
• Regeneration

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a . Fission

This activity mainly occurs in single-celled organisms such as bacteria, protozoa. In this, the organism divides into two or more identical daughter cells by asexual reproduction, which is called fission. Before fission D.N.A. Duplication takes place, followed by cell division.

If a single organism divides into two equal parts in the process of fission, then it is called binary fission. Like – Bacteria, Amoeba, Paramecium etc.

If the organism divides into more than two parts in the process of fission, then it is called multiple fission. Like – in the parasite Plasmodium of malaria disease.

b . Fragmentation

In this a single celled organism grows in length and is broken into two or more parts by some external force. Each part divided in this way gives rise to a new organism or a new progeny. It is mainly found in fungi, algae and bacteria.

c . Budding

In this, external growth or bud is formed on the outer body of the organism. After this bud grows in size, it separates from the parent organism and starts living life as an independent organism. In this way a new offspring organism is formed. This action mainly takes place in yeast, hydra.

d . Sporulation or Sporogenesis

In this, spores are formed in organisms or plants of the plant class. It is of the following types –

• Zoospores
• Aplanospores
• Conidia
• Chlamydospores

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( i ) Zoospores

Mobile spores are formed under favorable conditions. Flagella are found in these, due to which they are able to move. That is why they are called mobile spores. Like – in rhizobium (bacteria), in fungi and in algae.

( ii ) Aplanospores

Formation of immotile spores takes place under adverse conditions. Flagella are not found in them, due to which they are unable to move. Like - in fungi, in algae.

In this process, spores are formed at the top of plants by mitosis. Spores are microscopic, unicellular and nucleated. The number of spores formed in it are innumerable. These spores give birth to new progeny under favorable conditions. But most of the spores are destroyed, because due to their small size, the amount of stored food in them is very less.

( iii ) Conidia

These are also immobile exogenous spores, which are formed on the front part of the fungi. The mycelium on which they are formed is called Conidiophore. Like – in fungi like Pythium and Penicillium.

( iv ) Chlamydospores

These are thick walled spores, which are formed under adverse conditions. Like – in Rhizopus, Mucor etc.

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e . Gemmul

They are formed in adverse conditions. These are internal buds, which are formed by accumulation of cells or protoplasm. Under favorable conditions, new organisms are formed from them.

f. Regeneration

Regeneration means re-emergence. When any part of the body of an organism or plant is damaged, the coming back of that part again is called Regeneration.

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