Asexual Reproduction in Plants
Category : 8th Class
Introduction
Reproduction is the biological process, which helps us to produce new offspring or individuals of similar types. It is a fundamental feature of all living organ isms.
There are two methods of reproductions: sexual and asexual.
In asexual reproduction, single individual can reproduce without involvement with another individual of that species. For example, the division of a bacterial cell into two daughter cells or reproductions in plant. In sexual reproduction, two organisms are involved in the process of reproduction. The two organisms are male and female of a particular species.
Asexual Reproduction in Plants
In asexual reproduction, the organisms creates genetically similar or identical copy of itself. There is no contribution of genetic material from other individuals. Many single cellular organisms, like bacteria can divide asexually via binary fissions. Some other organisms, like amoeba and hydra also produce by binary
fissions. The different methods of asexual reproductions are: fission, regeneration, budding, spore formations, vegetative propagations and fragmentations. Virus reproduces in the body of the host to produce more organisms of its kind. Hydra and yeasts are produced by budding. These organisms often do not possess different sexes. They are capable of breaking themselves into two or more cell and develop into individuals. Most of the plants are capable of reproducing by the process of vegetative propagations. In this process, the new plants are produced form the parts of the parent plants. For example, Bryophyllum, potato, tuber plants etc.
Bryophyllum Tuber Potato
Stems
In some plants species, stems develop new roots when exposed to suitable conditions, forming new plants. The horizontal above-ground stems, called stolons, of the strawberry produce new daughter plants at alternate nodes. In some plants underground stems produce new plants. For example, rhizomes, bulbs, corns and tubers.
Leaves
Some plants, such as, Bryophyllum reproduce through their leaves.
Roots
Some plants such as dandelion, poplar or aspen, use their root for reproduction.
They send up new stems from their roots, which develop into new plants.
Grafting
This method is widely used for propagating desired variety of shrub or tree. All the varieties of apple is propagated by this method.
There are two different methods of reproduction, asexual and sexual. Which one of the following organisms reproduces by asexual method?
(a) Cats
(b) Birds
(c) Humane
(d) Hydra
(e) None of these
Answer: (d)
Explanation
In cats, birds and human beings both male and female are separate, and hence they cannot reproduce by the asexual method. Hydra is a unicellular organism and hence reproduces by asexual method.
There are different methods of asexual reproductions. Which one of the following organisms given below reproduce by binary fission?
(a) 
(b) 
(c) 
(d) 
(e) None of these
Answer: (a)
Explanation
Since we know that option B, C, D, are multicellular and A is unicellular flagella, hence it reproduce by binary fission.
A sexual Reproduction in Animals
There are some animals, which reproduce by the process of asexual reproduction. The different methods of asexual reproductions are:
Budding
In this method, the organism develops a out-growth on its body. This out growth gets detached after some time and grow independently. The organisms like jellyfish and echinoderms, develops bud on their body which breaks away as they grows up and takes up an independent existence. Other animals like corals, the bud remains attached to the parent and form colonies of animals. This method is also common in parasitic animals like tapeworms.
Fragmentation
In this method, the organism spontaneously breaks up into several pieces, and each piece develops into separate individuals. For example, the spirogyra reproduces by this method.
Parthenogenesis
In this method the female produces egg, which develops into young one without ever being fertilized. It is also known as virgin birth. This method of reproductions is found in many fish, few species of frogs and lizard.
There are many animals, which reproduce by the asexual methods. There are different methods of asexual reproduction and Parthenogenesis is one such method. Which one of the following organisms reproduces by this method?
(a) Komodo
(b) Aphids
(c) Tapeworm
(d) Hydra
(e) None of these
Answer: (b)
Explanation
Only Aphids reproduces by Parthenogenesis, and rest reproduce by other methods of asexual reproduction. There are many microorganisms, which reproduce by the asexual method. Which one of the following organisms reproduce by asexual method?
(a) Bacillus
(b) Fly
(c) Mosquito
(d) Silk moth
(e) None of these
Answer: (a)
Explanation
Only Bacillus reproduce by binary fission, and rest of the organism reproduce by sexual method.
Sexual Reproduction
The method of reproduction, in which both male and female are involved, is called sexual reproduction. The male and female mate with each other, and their egg fertilized to produce the new offspring. Each of the two parents contributes half of the offspring genetic makeup by creating the haploid gametes. In these anisogamous species, the male produces sperm and female produces ova. In isogamous species, the gametes are similar, but they have separable properties. For example, the green algae, chlamydomonas, reinhardtii. There are many animals and plants, which reproduce sexually. The new offspring inherit the trait of both the parents. In plants, Bryophytes reproduces sexually; but they are normally haploid which produce gametes.
Allogamy
In this method, the ovum of one individual fertilized with the spermatoza of another individual.
Autogamy
It is also known as self fertilization, which occurs in hermaphrodite organisms. In this organisms, both the male and female sex are present in the same individual.
Mitosis and Meiosis
There are the two methods of cell division, mitosis and meiosis. The mitosis occurs in somatic cells, where as meiosis occurs in reproductive cell orgametes. In mitosis, the number of cell after the cell division is doubled, but the number of chromosomes remains the same as in the parent cell. In meiosis, the number of cell becomes four times, but the number of chromosomes is reduced to half. This process occurs in two phase, meiosis I and meiosis II.
There are different methods of cell division in the multicellular organisms, which helps in its growth and development. The method of cell division, which takes place in the reproductive cell for reproductions is?
(a) Mitosis
(b) Meiosis
(c) Prophase
(d) Anaphase
(e) None of these
Answer: (b)
Explanation
The cell division in the reproductive cell is by the method of meiosis and cell division in rest of the body parts is through mitosis.
Some organisms have both the sex, while, most of the other multicellular organisms have male and female on different organisms. The organisms, in which have both male and female sex are present is called hermaphrodite. Which one of the following organisms given below is hermaphrodite?
(a) Leach
(b) Earthworm
(c) Tapeworm
(d) Silkworm
(e) None of these
Answer: (b)
Asexual vs. Sexual Reproduction
The organisms, which reproduces sexually tend to grow exponentially in numbers, but rely on mutation for variations in DNA. They have similar vulnerabilities. The organisms that reproduce sexually, yield less number of offspring. They show large amount of variations in their genetic make up. It makes them less susceptible to disease. There are many organisms that can reproduce both sexually and asexually. For example, aphids, slime molds, sea anemones, some species of starfish and many species of plants. Asexual reproduction is employed when the environmental conditions, such as, abundant food supply, adequate shelter, favorable climate, etc is suitable for survival. When these conditions get depleted, the organism switch on to sexual mode of reproductions. The variations found in the offspring are more, that reproduce through sexual mode. The variations in the offspring help them to survive better in the changing climatic conditions. In addition/sexual reproduction usually results in the formation of life stage that endures the conditions, which threatens the offspring of an asexual parent. Thus, the seeds, spores, eggs, pupae, cysts or other "over-wintering" stages of sexual reproduction ensure the survival during unfavorable conditions. The organism can "wait out" adverse conditions until a swing back to suitability occurs.
Why to Choose Asexual Reproduction
The sexual reproduction is more efficient way to reproduce more organisms. Sexual reproductions requires both male and female for the process to be completed. Two general explanations for the overwhelming prevalence of sexually-reproducing species over asexual ones are:
(i) It provides a mechanism to weed out harmful mutations, that arise in the population reducing its fitness.
(ii) Perhaps it is the ability to adapt quickly to a changing environment, which has caused sex to remain the method of choice for most living things.
The population of the organisms, which reproduces by the sexual method is large, as compared to the population of the organisms reproduce by the sexual method. In asexual method, large number of new organisms is produced at a time. Thus, we can say that the number of population in asexual reproduction increases_______.
(a) Proportionally
(b) Inversely
(c) Exponentially
(d) Linearly
(e) None of these
Answer: (c)
Explanation
The population in asexual method increases exponentially.
Which of the following statement is correct?
Statement 1: In asexual reproduction, the organisms rely on mutation for variation in DNA.
Statement 2: In asexual reproduction the organism can reproduce in different condition.
(a) Both the statement 1 and 2 are correct
(b) Statement 1 is correct and 2 is incorrect
(c) Statement 1 is incorrect and 2 is correct
(d) Both statement 1 and 2 are incorrect
(e) None of these
Answer: (a)
Explanation
Since both the statement I and II regarding the asexual reproduction is correct..
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