Asexual Reproduction | Biology
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Asexual Reproduction | Biology

Hey students so as you know that reproduction is a means to produce new Offsprings. These offsprings or organisms produces are very much similar to their parents. But we know that there are subtle differences between the parents and the offsprings. Let us learn why this happens? We know that the chromosome present in the nucleus of the cell, contains the information of inheritance in the form of DNA. And the DNA expresses this information in the form of protein. So the basic event in reproduction is to make a copy of this DNA. Now, the copy of this DNA is made by some biochemical reactions and as we know that no reaction can create an exact copy of the DNA rather some errors are always expected. And this will produce some variations which will occur in the progeny. Now the question arises that what is the importance of these variations. Well, we know that there can be some changes in the environment around the organisms. For example, temperature can go up or down, water presence may change etc. Now, if the population of an organism is well-suited for a particular environment and it that environment changes the whole population is more likely to be wiped out. But if there are some variations in the populations, those variations can help in the survival of that population in that changing environment. And so we say that variations are useful for a population. Having discussed that how these variations are produced in these progenies. And what is their importance, Let’s see different modes by which these progenies are produced. The process of production of progenies or offsprings is known as reproduction. Now this reproduction occurs either by a single individual or by the involvement of both the sexes. That is by the involvement of both, male and female. When the reproduction occurs by a single individual it is known as asexual reproduction. While when the reproduction occurs with the involvement of both the sexes that is male and female it is known as sexual reproduction. In this lesson we’ll mainly study about asexual reproduction there are various methods by which individuals divide asexually. For example, fission, fragmentation regeneration, budding, vegetative propagation and spore formation. We’ll discuss all of them one by one Let’s start with fission, fission means dividing or splitting. So in this the organism divides or splits as a whole. It is mainly found in all unicellular organisms. There are two types of fissions. First, binary fission second multiple fission. Now in binary fission the organism divides or splits in two parts. For example, it occurs in bacteria, amoeba paramecium, etc. Depending on the plane of cell division, binary division can be of three types. First, organism can split from Tranverse plane. For example, in bacteria, protozoa, etc. Second organisms can split from any plane. For example in Amoeba and third, organisms can split longitudinally. For example, in leishmania. It is also known as kala-azhar. It is a protozoan. So it has a whip like structure called flagellum. at the end of itself and that’s to divide the cell into two equal halves it has to divide longitudinally. A second type of fission is multiple vision. In which the organisms divide into many. So some organisms they have continuous division and produce many daughter cells simultaneously. For example, malarial parasite, plasmodium. Next method of asexual reproduction is fragmentation. It is mainly present in multicellular organisms with simple body organization. For example, in spirogyra. It is a green algae. It has filamentous structure. When it matures it breaks down into various elements or pieces and these pieces then give rise to the new individuals. Now we’ll see what is regeneration. In this process fully diifferentiated organisms give rise to new organisms from their body parts. They do this with the help of specialized cells. Which can make all the types of cells in the body. Hydra and planaria show regeneration we can see regeneration process in planaria. If the body of the planaria is cut into many pieces, then each piece will grow into a new individual. Next method is budding. It is also present in hydra. Regenerative cells in hydra are responsible for budding. This budding is the result of repeated cell division at a particular site. It is nothing but just an outgrowth. When this bud matures, they detached from the body of the parents and then they grow as new individuals. Next we study about vegetative propagation. This type of reproduction occurs in plants. When new plants are developed from vegetative parts of the plant, like roots, stems and leaves. It is known as vegetative propagation. Vegetative propagation occurs naturally in many plants, for example, in bryophyllum. You might have seen the lives of bryophyllum. It has buds all around its margins. When these leaves fall into soil, new plants emerge. There are many advantages of vegetative propagation. Like first, the plants can bear fruits and flowers at much earlier stage than other plants. Second, the plants which have lost the capacity to bear seeds, can also grow for example, banana, rose, jasmine, etc. And third the plants produced by this method are genetically similar to the parents and so they share the same characteristics. Nowadays many farmers and gardeners are using artificial methods of vegetative propagation like cutting, grafting, layering, etc. By these methods many plants like Rose, grapes, sugarcane, etc are grown. You might be amazed to know that scientists and plant biologists have found new techniques to grow plants they remove the cells or tissues from the growing tip of the plants and place these cells or tissues in artificial medium. After repeated division, a mass of cells is formed in this medium. This mass of cells is known as callus. This callus is then again place in another artificial medium which contains hormones for its growth and differentiation. From this callus plantlets are seen to be growing out and these plantlets are planted in soil for for the plant development. This technique of growing plants is known as tissue culture. By this technique, many plants can be grown by a single plant in disease free conditions. Many ornamental plants are grown by using this tissue culture technique. Lastly we’ll study about spore formation. If you keep a wet bread slice for 3-4 hours in cool, moist and dark place. You’ll find a greenish appearance on it. These greenish substances are fungus or bread mold called rhizopus. This rhizopus has hyphae and sporangia in it. If you observe it with magnifying glasses, You’ll find this type of structure. These filaments are called hyphae. These are non- reproductive structures of rhizopus. While this blob on a stick like structure is called sporangia. These are the reproductive structures of rhizopus. This sporangia contains spores in them. And these spores are surrounded by a thick wall, which protects it. Dehiscence these spores in moist environment develops new rhizopus. So in this lesson we learned that how variations occur in the progenies and why they’re important. Next we saw about the modes of asexual reproduction. Which are fission, fragmentation, regeneration, budding, vegetative propagation and spore formation.

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