Reproduction is the process by which organisms carry their progeny forward. Reproduction is mainly of two types – Sexual Reproduction and Asexual Reproduction. Asexual reproduction is the type of reproduction process in which an offspring is produced without the involvement of gametes or sex cells. The other type of reproduction, commonly found in which an offering is produced from two biological parents, is called Sexual Reproduction.
Advantages and Disadvantages of Asexual Reproduction
The asexual process of reproduction has some advantages and disadvantages. Some of them are listed below:
Reproduction, and hence population growth, takes place at a rapid pace.
This method of reproduction takes place faster than sexual reproduction.
One parent is sufficient to contribute to the population of the species.
It is an investment using a lower resource.
Members of the species are exact lookalikes. Hence, there is a lack of diversity among the members of the species born by the asexual method of reproduction. The genetic diversity in them is by their mutation rate.
Offsprings of a species born by the process of asexual reproduction get affected by the same species, deficiencies of nutrients and environmental hardships.
Types of Asexual Reproduction
Asexual Reproduction can be of the following types:
Budding: In this type of reproduction, a part of the individual splits off, and an offspring grows out of the body of the parent organism. Budding generally takes place in certain specialised areas. However, there are also a few instances when the buds come out of any place on the parents’ bodies. The offspring does not detach from the body of the parent till the time it is immature. Some organisms which practice budding are single-celled eukaryotes, such as yeast, hydras, etc.
Binary Fission: In this type of reproduction, one cell divides to produce two identical cells, which grow up to the parent cell’s size. Prokaryotes such as bacteria, archaebacteria, and some protozoa are produced by binary fission. In this method, it copies DNA and splits it into two. Thus, each “daughter cell” gets a copy of the DNA.
Vegetative Propagation: This type of reproduction is similar to that of budding. In this process, a plant grows a new shoot. This shoot can develop into a whole new organism by itself. This process by which a part which evolves from the vegetative parts of the plant, such as stems, leaves and roots, can grow into a completely new plant by itself is called vegetative propagation. This process does not require pollination for the reproduction process. New plants are grown out of the vegetative parts of the existing plants. Horticulturists and gardeners use this method to grow plants that are economically important. Vegetative propagation can be of two major types: natural and artificial. Strawberry is a plant which grows by the method of vegetative propagation.
Sporogenesis: “Spora” means seeds and “genesis” means origin. Sporogenesis is the method of production of reproductive cells, call spores, which grow to develop into a new organism. Sports are similar to seeds. The difference between the two is that spores do not have embryo. Hence this process does not require fertilisation between the male and female gametes. Spores are distributed by carriers such as wind. Examples of organisms which reproduce by the formation of spores include vascular plants and fungi.
Fragmentation: The body of a parent breaks into distinct segments. Each of these segments is capable of producing offspring. Fragmentation differs from budding and vegetative propagation in that, in fragmentation, one parent organism is split into multiple similar-sized parts to produce many offsprings. In contrast, in budding and vegetative propagation, the offspring have smaller parts than the parents. Earthworms, animals such as sponges, stars, planarians, and many annelid worms, fungi, such as yeasts, lichens, moulds, vascular and nonvascular plants, and cyanobacteria are examples of organisms that can reproduce by the process of Fragmentation.
Parthenogenesis: This type of reproduction involves the development of an egg, but the egg has not been fertilised into an individual. Wasps, bees and ants reproduce through this process.
Regeneration: In this process, a new individual develops from a part of another individual. In this process, a part of the parent’s body detaches from it. This separated part grows and develops into a completely new individual. Echinoderms are an example of organisms which produce through regeneration.
Apoximis: In this method, plants reproduce without fertilization. Bryophytes and ferns reproduce by means of this process. In plants that produce flowers, seeds produced from unfertilised ovules are called agamospermy. There are two major types of apomixis: gametophytic apomixis and sporophytic apomixis. Gametophytic apomixis is a process in which an embryo arises from an unfertilised ovum from a gametophyte that did not complete the meiosis process. Diplospory and Apospory are two major types of gametophytic apomixis.
Methods of Asexual Reproduction
Asexual reproduction can take place through natural methods as well as artificial methods.
Natural methods of sexual reproduction include ways in which plants self-propagate. Plants such as ginger, onion, gladioli, and dahlia reproduce by natural methods. These plants grow from buds present on the stem’s surface.
Grafting, Cutting, Layering, and Micropropagation are methods by which plants reproduce by asexual reproduction.
Grafting – Grafting is a method of asexual reproduction in plants through artificial means in which two plants combine to form a new hybrid variety. Part of the stem of the desired plant is grafted onto a rooted plant. Viticulture (growing of grapes) and the citrus industries widely use grafting.
Cutting – In this method, a portion of the stem containing nodes and internodes is placed in moist soil and allowed to root. Stems in some species of plants can produce roots even when they are placed only in water. For example – Money plant, Coleus, African violet.
Layering – The stem attached to the plant is lowered and covered with soil. For example – Bougainvillea.
Micropropagation – In this method, a large number of plants are propagated from a single plant, in a short time, under laboratory conditions. This process is also widely known as plant tissue culture.
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