Content Writer | Updated On - Oct 17, 2024
Asexual reproduction is a biological process by which new organisms are produced by a single parent organism without the formation of gametes. The offsprings produced during asexual mode of reproduction are always identical to their parents. This is an efficient mode of reproduction in which multiplication and growth are rapid.
The common types of asexual reproduction which are mainly observed in lower organism and some plants include budding, binary fission, propagation etc. It is common among single-celled organisms and in plants having a relatively simple organisation, like in algae and fungi. The number of chromosomes remains same during the process of asexual reproduction.
What is Asexual Reproduction?
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Asexual reproduction is a mode of reproduction where the union of male and female gametes does not occur, unlike sexual reproduction. In this type, new organisms can be produced with the participation of single parent only. Moreover, parthenogenesis is also an important type of asexual reproduction that takes place in vertebrates.
- The asexually produced offsprings are a clones of their parent i.e. they are exact copies of the parent organism.
- Bacteria, archaea, fungi, and many plants are examples of organisms that reproduce asexually.
- This process is observed both in unicellular and multicellular organisms.
- Potatoes, ginger, and strawberries are some of the examples of plants that reproduce asexually.
Types of Asexual Reproduction
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Different types of asexual reproduction take place in both single-celled and multi-celled organisms. These are as follows:
- Binary Fission
- Budding
- Sporulation
- Fragmentation
- Vegetative Propagation
Binary fission
Binary fission in asexual reproduction is one of the simplest forms of reproduction, in which the parental cell equally divides into two new daughter cells and each cell rapidly grows into an adult. Each cell has its own nucleus which is identical to its parent, the daughter cells mature and divide further. Examples of binary fission are Euglena, bacteria, amoeba, paramoecium.
Binary Fission in Amoeba
Budding
Budding is another type of asexual reproduction where new organisms produce from the small buds that remain attached to the parent cell until maturation is attained. The Two types of budding seen in fungi and algae are mentioned below:
Exogenous budding
This type of budding occurs outside the parent body and is also known as external budding. This is most commonly found in yeast, hydra, obelia, scyphus.
Endogenous budding
This type of budding occurs inside the parent body and is also known as Internal budding. This is most commonly found in Spongilla.
Budding in Yeast
Sporulation
Spore formation or Sporulation is a process where an organism reproduces via spores. Spores are usually microscopic, adapted for dispersal and can survive an extended period of unfavourable conditions that mature when met with favourable conditions. Under unfavourable conditions, these organisms produce spores in a sac-like structure called sporangium.
- Under suitable conditions, the sporangium bursts and the spores spread out.
- These spores germinate to give rise to new individuals.
- Amoeba and mushrooms reproduce by the formation of spores. The favourable conditions are moisture, optimal temperature, oxygen availability and Nutrients.
- Different types of spores are produced by different organisms.
Endogenous spores
These spores are produced inside the sporangia, for example, Rhizopus
Exogenous spores
These spores are produced on the conidiophores, for example, Penicillium, and Aspergillus.
Zoospores
They are microscopic structure with flagella that helps in motility. Zoospores are also called swarm spores or plant spores.
Aplanospores
It is an asexual microscopic structure without flagella, for example Algae.
Fragmentation
The asexual mode of reproduction where a body breaks into a number of fragments and each fragment thus develops into a mature individual is called Fragmentation. This process occurs in both plants and animals.
- Examples of animals in which fragmentation occurs are starfish, annelids, flatworms, and sponges.
- Cyanobacteria, algae and mushrooms are some other examples.
Vegetative propagation
Vegetative propagation of plants is a reproduction mode that occurs in plants’ vegetative parts like roots, stems, and leaves. The different parts of plants are runner, rhizome, sucker, tuber, offset, and bulb, which are all capable of giving rise to new offspring. These structures are called vegetative propagules.
The table below shows the different types of vegetative propagules:
| Vegetative Propagules | Functions | Examples |
|---|---|---|
| Rhizome | A modified, horizontally growing underground stem that can produce roots and shoots to form new organisms. | Ginger |
| Corms | It is a modified, fleshy, and vertically growing underground stem that can be cut into pieces to grow new plants. | Colocasia |
| Tuber | It is a modified underground stem with asexual buds or swollen structures called eyes. | Tuber include potato, sunchokes, ginger, etc. |
| Bulb | A short, modified underground stem with modified fleshy leaves that stores food within the stem | Onion, garlic, tulip, dutch iris, etc. |
| Runner | It is a sub-aerial stem modification that spreads to new niches and results in the formation of new plants when older parts of the plant die. | Oxalis and strawberries. |
| Stolon | A slender, lateral branch arising from the base of the main axis and arches down to touch the ground, producing adventitious roots. | Rosa and Nerium |
| Sucker | Lateral branches that originate from the basal and underground portion of the main axis. | Banana and Pineapple |
| Bulbils | These are modified vegetative or floral buds that are capable of producing new plants. | Dioscorea and Agave |
| Reproductive leaves | It is a leaf modification with adventitious epiphyllous buds present in notches of leaf margins that can generate new individuals when they come in contact with soil. | Bryophyllum Daigremontianum and peperomia |
| Off-Sets | These are horizontal branches arising from the base of the plant and buds and give rise to a new plant. Off-sets are creepers and spread all over the water body in a short period of time. | Water hyacinth or Terror of Bengal |
Advantages of asexual reproduction
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The main advantages of asexual reproduction are given below.
- Minimal requirements of energy for reproduction.
- It occurs in different environments as asexual organisms can readily adapt to any environment.
- The offspring mature in a relatively short time.
- Key traits of a parental organism are passed on to the next generation.
- Several asexual modes of reproduction are available.
- In plants, this process eliminates the need for asexual reproduction.
- Damaged plants can be easily rehabilitated by propagation.
Disadvantages of asexual reproduction
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Asexual reproduction also has a few disadvantages which are listed below:
- Any unnecessary modifications of genes within DNA are passed on to the next generations.
- As the reproduction process is easier, problems in population control arise.
- Poor resistance to pests.
- Lower life-span.
- Requirements of skills for cultivation.
- Some species might become habit-reliant for their survival.
- It can be an expensive process.
Things to Remember
- Asexual reproduction is defined as the process of reproducing without the fusion of gametes.
- Types of asexual reproduction involve budding, fission, vegetative propagation etc.
- Parthenogenesis is an asexual mode of reproduction where the female produces an embryo without fertilisation.
- Annelids, spirogyra, moulds, lichens, etc are examples of fragmentation.
- In budding, small buds remain attached to the parent cell until maturation.
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Multiple fission takes place when a parental body divides into many daughter organisms.
Previous Years Questions
- Meiosis takes place in...[NEET 2013]
- The sexual reproduction is absent in….[NEET 1995]
- For union between stock and scion in grafting which one is the first to occur….[NEET 1990]
- A clone is ......… [KCET 2011]
- Animals which possess cleidoic eggs exhibit….[KCET 2011]
- Which among these is not a post fertilization event ?...[KCET 2016]
- Type of asexual reproduction found in Hydra is..[KEAM]
- Which of the following is having longitudinal binary fission ?….[KEAM]
- In grafting, the stock and scion should be joined….
- Banana is vegetatively propagated by… [AMUEEE 2012]
- Vegetative propagation by leaves is seen in… [JKCET 2010]
- Vegetative propagation in water hyacinth takes place by...[AMUEEE 2013]
- A slender, prostrate subaerial branch of the stem which creeps along….
Sample Questions
Ques. Name the vegetative propagules in the following:(i)Agave (ii) Bryophyllum [All India 2014 C][1 mark]
Ans. The vegetative propagules are as follow:
(i) Bulbil is the vegetative propagule in agave.
(ii) Leaf buds are the vegetative propagule in bryophyllum
Ques. Write the name of the organism that is referred to as ‘Terror of Bengal’. [Delhi 2014][1 mark]
Ans. Water hyacinth is the plant which is also known as the ‘Terror of Bengal’.
Ques. Give one example each of a fungus which reproduces by: (i) budding (ii) conidia [Delhi 2014 C][1 mark]
Ans. An example of Fungus that reproduces by:
(i) Budding is yeast
(ii) conidia is penicillium
Ques. Give one example of a plant that reproduces by
(i) runner (ii) offset [Delhi 2014 C][1 mark]
Ans. A plant reproducing by runner is oxalis and a plant reproducing by offset is Pistia.
Ques. Name an organism, where cell division in itself is a mode of reproduction. [All India 2013; Foreign 2010][1 mark]
Ans. In the case of unicellular organisms, the cell division itself is a mode of reproduction .An example of the same is amoeba.
Ques. Name an alga that reproduces asexually through zoospores. Why are these reproductive units so called? [All India 2013][1 mark]
Ans. Chlamydomonas is the algae that reproduces through zoospores.
Ques. Which one of the following statements is true for yeast?
(i)The cell divides by binary fission. One of them develops into a bud.
(ii)The cell divides unequally. The smaller cell develops into a bud.
(iii)The cell produces conidia which develop into a bud. [Delhi 2013 C]
Ans. Statement (ii) is the true statement.
Explanation: in Yeast, budding is the mode of reproduction. The cell will divide unevenly and the smallest cell will form a bud. Conida bud is not referred to yeast and binary fission is seen in amoeba, euglena etc. Therefore, statement ii is correct.
Ques. How does Penicillium reproduce asexually? [Delhi 2013][1 mark]
Ans. Reproduction in penicillium is done asexually by Exogenous spores - i.e. spores are produced on the conidiophores.
Ques. Offsprings produced by asexual reproduction are called clones. Justify giving two reasons. [HOTS; all India 2010][1 mark]
Ans. In asexual reproduction, new organism or plant body is produced by a single parent with or without the involvement of gamete formation. Offsprings produced by asexual reproduction are identical to one another and also exact copies of their parent. They show ‘uniparental inheritance’. Thus, they are referred to as “Clones”.
Ques. Mention a characteristic feature and a function of zoospores in some algae. [All India 2010][1 mark]
Ans. (i) Characteristic feature: It is an asexual microscopic structure with flagella for motility.
(ii) Function: It helps in asexual reproduction of algae.
Ques. Identify this reproductive structure and name the organism they are being released from. [Delhi 2010][1 mark]
Ans. Structure: Zoospore, Organism: Chlamydomonas algae
Ques. Name the organism and the mode of reproduction represented in the diagram given below. [All India 2010][1 mark]
Ans. The organism shown in the image is yeast. The process of reproduction shown in the image is budding.
Ques. Banana crop is produced by farmers without sowing seeds. Explain how the plant is propagated? [All India 2014 C][2 marks]
Ans. The process of reproduction in plants without seeds is known as vegetative propagation. The vegetative propagule in banana (Musa accuminata) is Bulbils. These are modified vegetative or floral buds which produces new plants.
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