All the organisms produce offspring of their own types to continue their generation. Different organisms have different modes of reproduction.
Anyway, they increase their number for their existence.
Thus, reproduction is defined as a life process in which living organisms form offspring (child) of their own type to continue their generation.
In living organisms reproduction is carried out by different two methods. They are,
a. Asexual reproduction
Asexual reproduction is defined as the reproduction in which fertilization does not take place.
Offspring produced by this method are genetically similar to their parents.
Asexual reproduction is performed by very simple processes and in a short period.
The offspring formed by this method resembles exactly with their parents.
Asexual reproduction takes place by the following methods,
3. Fragmentation and regeneration
5. Vegetative propagation
The division of an organism into new organisms is called fission.
This type of reproduction mainly places in unicellular organisms.
When the individual cell is fully mature, it apart into two during favorable conditions.
Therefore, two almost equal-size daughter cell is produce.
This type of fission is binary fission.
This type of fission is very common in amoeba, bacteria, euglena, paramecium, etc.
In unfavorable conditions, a plasmodium in draws all its pseudopodia inwards and becomes about around.
The nucleus divides into a number of pieces and forms a hard layer at its surface called a cyst.
It can remain in this condition for several days and months.
When it gets favorable conditions again, the cyst breaks and each part of the nucleus comes out in the form of a new plasmodium.
This type of fission is multiple fission.
It is in Chlamydomonas, plasmodium, etc.
In budding, an organism produces a small outgrowth at one side.
The bud enlarges and later detaches from the parent’s body.
This is very common in hydra and yeast.
Then it grows into a new daughter organism.
In this method, an organism breaks into two or more fragments and each fragment grows into a new organism.
It is very common in tapeworm, starfish, and spirogyra.
Regeneration is the asexual reproduction in which the organism is divided into different parts, each part regenerates the missed parts and new organisms are formed.
It is in starfish, earthworm, planaria, tapeworm, hydra, etc.
It is a method of reproduction by spores. Most of the non-flowering plants lime mucor, mushroom, moss, ferns, etc. Produce spores inside their sporangium. Such spores come out when they mature. Then they germinate into their corresponding new plants under favorable conditions.
6. Vegetative propagation
Vegetative reproduction is the formation of new plants from some vegetative parts like leaf, stem, and root.
In this reproduction, any vegetative part goes detach from the parent plant and it is allow to grow.
The vegetative part that is taken to propagate should have a growing bud, sufficient food for the early growth and it should be capable of forming a new plant.
Pineapple, potato, rose, sugarcane, etc. Reproduce from their stem dahlia, sweet potato, etc. Reproduce by their roots. Bryophyllum reproduces by its leaves.
Importance of asexual reproduction
1. It is a simple and fast method of repro.
2. The purity of parental characters is maintained in offspring.
3. The plant which doesn’t form viable seeds also can increase their number by this process.
4. Offspring produced this by process get matured earlier relative to those which are formed by a sexual method.
b. Sexual reproduction
Sexual reproduction is a method of reproduction in which fertilization takes place.
In animals sperm is a male gamete and in plants pollen grains develop male gametes.
Similarly, ovum in animals and ovule in plants are female gametes.
The formation of Male gametes happens in the male reproductive organs like testes and androecium.
The formation of female gametes happens in the female reproductive organs like ovaries and gynoecium.
The fusion of male and female gametes is fertilization.
When fertilization is common in the frog, fish, etc.
When fertilization occurs inside the body, it is internal fertilization.
Humans, birds, insects, etc. Do this type of fertilization.
After fertilization, there is formation of zygote which develops into a new organism.
When the male and female reproductive organs are in separate organisms, they are unisexual or dioecious e.g. human, bird, frog, cucumber, etc.
But, when male and female reproductive organs exist in the same organism, it is bisexual or monoecious or hermaphrodite e.g. hydra, earthworm, tapeworm, mustard, etc.
Importance of sexual reproduction
1. It causes variation, which is the main unit of forming new species.
2. Offspring formed by this process have more disease resistance in them.
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