essay on types of asexual reproduction

5 Types of Asexual Reproduction

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All living things must reproduce in order to pass down genes to the offspring and continue to ensure the survival of the species.  Natural selection , the mechanism for  evolution , chooses which traits are favorable adaptations for a given environment and which are unfavorable. Those individuals with undesirable traits will, theoretically, eventually be bred out of the population and only the individuals with the "good" traits will live long enough to reproduce and pass down those genes to the next generation.

There are two types of reproduction: sexual reproduction and asexual reproduction. Sexual reproduction requires both a male and a female gamete with different genetics to fuse during fertilization, therefore creating an offspring that is different from the parents. Asexual reproduction only requires a single parent that will pass down all of its genes to the offspring. This means there is no mixing of genes and the offspring is actually a clone of the parent (barring any sort of  mutations ).

Asexual reproduction is generally used in less complex species and is quite efficient. Not having to find a mate is advantageous and allows a parent to pass down all of its traits to the next generation. However, without diversity, natural selection cannot work and if there are no mutations to make more favorable traits, asexually reproducing species may not be able to survive a changing environment.

Binary Fission

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Almost all prokaryotes undergo a type of asexual reproduction called binary fission. Binary fission is very similar to the process of mitosis in eukaryotes. However, since there is no nucleus and the DNA in a prokaryote is usually just in a single ring, it is not as complex as mitosis. Binary fission starts with a single cell that copies its DNA and then splits into two identical cells.

This is a very fast and efficient way for bacteria and similar types of cells to create offspring. However, if a DNA mutation were to occur in the process, this could change the genetics of the offspring and they would no longer be identical clones. This is one way that variation can occur even though it is undergoing asexual reproduction. In fact, bacterial resistance to antibiotics is evidence for evolution through asexual reproduction.

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Another type of asexual reproduction is called budding. Budding is when a new organism, or the offspring, grows off the side of the adult through a part called a bud. The new baby will stay attached to the original adult until it reaches maturity at which point they break off and become its own independent organism. A single adult can have many buds and many offspring at the same time.

Both unicellular organisms, like yeast, and multicellular organisms, like hydra, can undergo budding. Again, the offspring are clones of the parent unless some sort of mutation happens during the copying of the DNA or cell reproduction.

Fragmentation

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Some species are designed to have many viable parts that can live independently all found on one individual. These types species can undergo a type of asexual reproduction known as fragmentation. Fragmentation happens when a piece of an individual breaks off and a brand new organism forms around that broken piece. The original organism also regenerates the piece that broke off. The piece may be broken off naturally or could be broken off during an injury or other life threatening situation.

The most well known species that undergoes fragmentation is the starfish, or sea star. Sea stars can have any of their five arms broken off and then regenerated into offspring. This is mostly due to their radial symmetry. They have a central nerve ring in the middle that branches out into five rays, or arms. Each arm has all the parts necessary to create a whole new individual through fragmentation. Sponges, some flatworms, and certain types of fungi can also undergo fragmentation.

Parthenogenesis

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The more complex the species, the more likely they are to undergo sexual reproduction as opposed to asexual reproduction. However, there are some complex animals and plants that can reproduce via parthenogenesis when necessary. This is not the preferred method of reproduction for most of these species, but it may become the only way to reproduce for some of them for various reasons.

Parthenogenesis is when an offspring comes from an unfertilized egg. Lack of available partners, an immediate threat on the female's life, or other such trauma may result in parthenogenesis being necessary to continue the species. This is not ideal, of course, because it will only produce female offspring since the baby will be a clone of the mother. That will not fix the issue of lack of mates or carrying on the species for an indefinite period of time.

Some animals that can undergo parthenogenesis include insects like bees and grasshoppers, lizards such as the komodo dragon, and very rarely in birds.

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Many plants and fungi use spores as a means of asexual reproduction. These types of organisms undergo a life cycle called alternation of generations where they have different parts of their lives in which they are mostly diploid or mostly haploid cells. During the diploid phase, they are called sporophytes and produce diploid spores they use for asexual reproduction. Species that form spores do not need a mate or fertilization to occur in order to produce offspring. Just like all other types of asexual reproduction, the offspring of organisms that reproduce using spores are clones of the parent.

Examples of organisms that produce spores include mushrooms and ferns.

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Asexual Reproduction

Reviewed by: BD Editors

Asexual Reproduction Definition

Asexual reproduction occurs when an organism makes more of itself without exchanging genetic information with another organism through sex.

In sexually reproducing organisms, the genomes of two parents are combined to create offspring with unique genetic profiles. This is beneficial to the population because genetically diverse populations have a higher chance of withstanding survival challenges such as disease and environmental changes.

Asexually reproducing organisms can suffer a dangerous lack of diversity – but they can also reproduce faster than sexually reproducing organisms, and a single individual can found a new population without the need for a mate.

Some organisms that practice asexual reproduction can exchange genetic information to promote diversity using forms of horizontal gene transfer such as bacteria who use plasmids to pass around small bits of DNA. However this method results in fewer unique genotypes than sexual reproduction.

Some species of plants, animals, and fungi are capable of both sexual and asexual reproduction, depending on the demands of the environment.

Asexual reproduction is practiced by most single-celled organisms including bacteria, archaebacteria, and protists. It is also practiced by some plants, animals, and fungi.

Advantages of Asexual Reproduction

Important advantages of asexual reproduction include:

1. Rapid population growth. This is especially useful for species whose survival strategy is to reproduce very fast.

Many species of bacteria, for example, can completely rebuild a population from just a single mutant individual in a matter of days if most members are wiped out by a virus.

2. No mate is needed to found a new population.

This is useful for species whose members may find themselves isolated, such as fungi that grow from wind-blown spores, plants that rely on pollinators for sexual reproduction, and animals inhabiting environments with low population density.

3. Lower resource investment. Asexual reproduction, which can often be accomplished just by having part of the parent organism split off and take on a life of its own, takes fewer resources than nurturing a new baby organism.

Many plants and sea creatures, for example, can simply cut a part of themselves off from the parent organism and have that part survive on its own.

Only offspring that are genetically identical to the parent can be produced in this way: nurturing the creation of a new organism whose tissue is different from the parents’ tissue takes more time, energy, and resources.

This ability to simply split in two is one reason why asexual reproduction is faster than sexual reproduction.

Disadvantages of Asexual Reproduction

The biggest disadvantage of asexual reproduction is lack of diversity. Because members of an asexually reproducing population are genetically identical except for rare mutants, they are all susceptible to the same diseases, nutrition deficits, and other types of environmental hardships.

The Irish Potato Famine was one example of the down side of asexual reproduction: Ireland’s potatoes, which had mainly reproduced through asexual reproduction, were all vulnerable when a potato-killing plague swept the island. As a result, almost all crops failed, and many people starved.

The near-extinction of the Gros-Michel banana is another example – one of two major cultivars of bananas, it became impossible to grow commercially in the 20th century after the emergence of a disease to which it was genetically vulnerable.

On the other hand, many species of bacteria actually take advantage of their high mutation rate to create some genetic diversity while using asexual reproduction to grow their colonies very rapidly. Bacteria have a higher rate of errors in copying genetic sequences, which sometimes leads to the creation of useful new traits even in the absence of sexual reproduction.

Types of Asexual Reproduction

There are many different ways to reproduce asexually. These include:

1. Binary fission . This method, in which a cell simply copies its DNA and then splits in two, giving a copy of its DNA to each “daughter cell,” is used by bacteria and archaebacteria.

2. Budding . Some organisms split off a small part of themselves to grow into a new organism. This is practiced by many plants and sea creatures, and some single-celled eukaryotes such as yeast.

3. Vegetative propagation . Much like budding, this process involves a plant growing a new shoot which is capable of becoming a whole new organism. Strawberries are an example of plants that reproduce using “runners,” which grow outward from a parent plant and later become separate, independent plants.

4. Sporogenesis . Sporogenesis is the production of reproductive cells, called spores, which can grow into a new organism.

Spores often use similar strategies to those of seeds. But unlike seeds, spores can be created without fertilization by a sexual partner. Spores are also more likely to spread autonomously, such as via wind, than to rely on other organisms such as animal carriers to spread.

5. Fragmentation . In fragmentation, a “parent” organism is split into multiple parts, each of which grows to become a complete, independent “offspring” organism. This process resembles budding and vegetative propagation, but with some differences.

For one, fragmentation may not be voluntary on the part of the “parent” organism. Earthworms and many plants and sea creatures are capable of regenerating whole organisms from fragments following injuries that split them into multiple pieces.

When fragmentation does occur voluntarily, the same parent organism may split into many roughly equal parts in order to form many offspring. This is different from the processes of budding and vegetative propagation, where an organism grows new parts which are small compared to the parent and which are intended to become offspring organisms.

6. Agamenogenesis . Agamenogenesis is the reproduction of normally sexual organisms without the need for fertilization. There are several ways in which this can happen.

In parthenogenesis, an unfertilized egg begins to develop into a new organism, which by necessity possesses only genes from its mother.

This occurs in a few species of all-female animals, and in females of some animal species when there are no males present to fertilize eggs.

In apomoxis, a normally sexually reproducing plant reproduces asexually, producing offspring that are identical to the parent plant, due to lack of availability of a male plant to fertilize female gametes.

In nucellar embryony, an embryo is formed from a parents’ own tissue without meiosis or the use of reproductive cells. This is primarily known to occur in citrus fruit, which may produce seeds in this way in the absence of male fertilization.

Examples of Asexual Reproduction

All bacteria reproduce through asexual reproduction, by splitting into two “daughter” cells that are genetically identical to their parents.

Some bacteria can undergo horizontal gene transfer – in which genetic material is passed “horizontally” from one organism to another, instead of “vertically” from parent to child. Because they have only one cell, bacteria are able to change their genetic material as mature organisms.

The process of genetic exchange between bacterial cells is sometimes referred to as “sex,” although it is performed to change the genotype of a mature bacterium, not as a means of reproduction.

Bacteria can afford to use this survival strategy because their extremely rapid reproduction makes harmful genetic mutations – such as copying errors or horizontal gene transfer gone wrong – inconsequential to the whole population. As long as a few individuals survive mutation and calamity, those individuals will be able to rebuild the bacterial population quickly.

This strategy of “reproduce fast, mutate often” is a major reason why bacteria are so quick to develop antibiotic resistance. They have also been seen to “invent” whole new biochemistries in the lab, such as one species of bacteria that spontaneously acquired the ability to perform anaerobic respiration.

This strategy would not work well for an organism that invests highly in the survival of individuals, such as multicellular organisms.

Slime Molds

Slime molds are a fascinating organism that sometimes behave like a multicellular organism, and sometimes behave like a colony of single-celled organisms.

Unlike animals, plants, and fungi, the cells in a slime mold are not bound together in a fixed shape and dependent on each other for survival. The cells that make up a slime mold are capable of living individually and may spread or separate when food is abundant, much like individuals in a colony of bacteria.

But slime mold cells are eukaryotic, and can display a high degree of cooperation to the point of creating a temporary extracellular matrix and a “body” which may become large and complex. Slime molds whose cells are working cooperatively can be mistaken for fungi, and can perform locomotion.

Slime molds can produce spores much like a fungus, and they can also reproduce through fragmentation. Environmental causes or injury may cause a slime mold to disperse into many parts, and units as small as a single cell may grow into a whole new slime mold colony/organism.

New Mexico Whiptail Lizards

This species of lizard was created by the hybridization of two neighboring species. Genetic incompatibility between the hybrid parents made it impossible for healthy males to be born: however, the female hybrids were capable of parthenogenesis, making them a reproductively independent population.

All New Mexico whiptail lizards are female. New members of the species can be created through hybridization of the parent species, or through parthenogenesis by female New Mexico whiptails.

Possibly as a remnant of their sexually reproducing past, New Mexico whiptail lizards do have a “mating” behavior which they must go through to reproduce. Members of this species are “mated with” by other members, and the lizard playing the female role will go onto lay eggs.

It is thought that the mating behavior stimulates ovulation, which can then result in a parthenogenic pregnancy. The lizard playing the “male” role in the courtship does not lay eggs.

Related Biology Terms

• Gamete – Sexual reproductive cells, which contain half of the parent organism’s genetic material.
• Reproductive strategy – A strategy that describes how a given population uses its resources to produce offspring.
• Sexual Reproduction – A means of reproduction in which the genetic material of two parents is combined to produce offspring with a unique genetic profile.

2. Which of the following events was NOT caused by low genetic diversity due to asexual reproduction? A. The Irish Potato Famine B. The disappearance of the Gros-Michel banana C. The Black Death in England D. A and B Answer to Question #2 C is correct. Europeans survived the Black Death in England, perhaps in part because of genetic diversity due to sexual reproduction.

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32. Plant Reproduction

Asexual reproduction, learning objectives.

By the end of this section, you will be able to do the following:

• Compare the mechanisms and methods of natural and artificial asexual reproduction
• Describe the advantages and disadvantages of natural and artificial asexual reproduction
• Discuss plant life spans

Many plants are able to propagate themselves using asexual reproduction. This method does not require the investment required to produce a flower, attract pollinators, or find a means of seed dispersal. Asexual reproduction produces plants that are genetically identical to the parent plant because no mixing of male and female gametes takes place. Traditionally, these plants survive well under stable environmental conditions when compared with plants produced from sexual reproduction because they carry genes identical to those of their parents.

Many different types of roots exhibit asexual reproduction ( (Figure) ). The corm is used by gladiolus and garlic. Bulbs, such as a scaly bulb in lilies and a tunicate bulb in daffodils, are other common examples. A potato is a stem tuber, while parsnip propagates from a taproot. Ginger and iris produce rhizomes, while ivy uses an adventitious root (a root arising from a plant part other than the main or primary root), and the strawberry plant has a stolon, which is also called a runner.

Figure 1. Different types of stems allow for asexual reproduction. (a) The corm of a garlic plant looks similar to (b) a tulip bulb, but the corm is solid tissue, while the bulb consists of layers of modified leaves that surround an underground stem. Both corms and bulbs can self-propagate, giving rise to new plants. (c) Ginger forms masses of stems called rhizomes that can give rise to multiple plants. (d) Potato plants form fleshy stem tubers. Each eye in the stem tuber can give rise to a new plant. (e) Strawberry plants form stolons: stems that grow at the soil surface or just below ground and can give rise to new plants. (credit a: modification of work by Dwight Sipler; credit c: modification of work by Albert Cahalan, USDA ARS; credit d: modification of work by Richard North; credit e: modification of work by Julie Magro)

Some plants can produce seeds without fertilization. Either the ovule or part of the ovary, which is diploid in nature, gives rise to a new seed. This method of reproduction is known as apomixis.

An advantage of asexual reproduction is that the resulting plant will reach maturity faster. Since the new plant is arising from an adult plant or plant parts, it will also be sturdier than a seedling. Asexual reproduction can take place by natural or artificial (assisted by humans) means.

Natural Methods of Asexual Reproduction

Natural methods of asexual reproduction include strategies that plants have developed to self-propagate. Many plants—like ginger, onion, gladioli, and dahlia—continue to grow from buds that are present on the surface of the stem. In some plants, such as the sweet potato, adventitious roots or runners can give rise to new plants ( (Figure) ). In Bryophyllum and kalanchoe, the leaves have small buds on their margins. When these are detached from the plant, they grow into independent plants; or, they may start growing into independent plants if the leaf touches the soil. Some plants can be propagated through cuttings alone.

Figure 2. A stolon, or runner, is a stem that runs along the ground. At the nodes, it forms adventitious roots and buds that grow into a new plant.

Artificial Methods of Asexual Reproduction

These methods are frequently employed to give rise to new, and sometimes novel, plants. They include grafting, cutting, layering, and micropropagation.

Grafting has long been used to produce novel varieties of roses, citrus species, and other plants. In grafting, two plant species are used; part of the stem of the desirable plant is grafted onto a rooted plant called the stock. The part that is grafted or attached is called the scion. Both are cut at an oblique angle (any angle other than a right angle), placed in close contact with each other, and are then held together ( (Figure) ). Matching up these two surfaces as closely as possible is extremely important because these will be holding the plant together. The vascular systems of the two plants grow and fuse, forming a graft. After a period of time, the scion starts producing shoots, and eventually starts bearing flowers and fruits. Grafting is widely used in viticulture (grape growing) and the citrus industry. Scions capable of producing a particular fruit variety are grafted onto root stock with specific resistance to disease.

Figure 3. Grafting is an artificial method of asexual reproduction used to produce plants combining favorable stem characteristics with favorable root characteristics. The stem of the plant to be grafted is known as the scion, and the root is called the stock.

Plants such as coleus and money plant are propagated through stem cuttings, where a portion of the stem containing nodes and internodes is placed in moist soil and allowed to root. In some species, stems can start producing a root even when placed only in water. For example, leaves of the African violet will root if kept in water undisturbed for several weeks.

Layering is a method in which a stem attached to the plant is bent and covered with soil. Young stems that can be bent easily without any injury are preferred. Jasmine and bougainvillea (paper flower) can be propagated this way ( (Figure) ). In some plants, a modified form of layering known as air layering is employed. A portion of the bark or outermost covering of the stem is removed and covered with moss, which is then taped. Some gardeners also apply rooting hormone. After some time, roots will appear, and this portion of the plant can be removed and transplanted into a separate pot.

Figure 4. In layering, a part of the stem is buried so that it forms a new plant. (credit: modification of work by Pearson Scott Foresman, donated to the Wikimedia Foundation)

Micropropagation

Micropropagation (also called plant tissue culture) is a method of propagating a large number of plants from a single plant in a short time under laboratory conditions ( (Figure) ). This method allows propagation of rare, endangered species that may be difficult to grow under natural conditions, are economically important, or are in demand as disease-free plants.

Figure 5. Micropropagation is used to propagate plants in sterile conditions. (credit: Nikhilesh Sanyal)

To start plant tissue culture, a part of the plant such as a stem, leaf, embryo, anther, or seed can be used. The plant material is thoroughly sterilized using a combination of chemical treatments standardized for that species. Under sterile conditions, the plant material is placed on a plant tissue culture medium that contains all the minerals, vitamins, and hormones required by the plant. The plant part often gives rise to an undifferentiated mass known as callus, from which individual plantlets begin to grow after a period of time. These can be separated and are first grown under greenhouse conditions before they are moved to field conditions.

Plant Life Spans

The length of time from the beginning of development to the death of a plant is called its life span. The life cycle, on the other hand, is the sequence of stages a plant goes through from seed germination to seed production of the mature plant. Some plants, such as annuals, only need a few weeks to grow, produce seeds and die. Other plants, such as the bristlecone pine, live for thousands of years. Some bristlecone pines have a documented age of 4,500 years ( (Figure) ). Even as some parts of a plant, such as regions containing meristematic tissue—the area of active plant growth consisting of undifferentiated cells capable of cell division—continue to grow, some parts undergo programmed cell death (apoptosis). The cork found on stems, and the water-conducting tissue of the xylem, for example, are composed of dead cells.

Figure 6. The bristlecone pine, shown here in the Ancient Bristlecone Pine Forest in the White Mountains of eastern California, has been known to live for 4,500 years. (credit: Rick Goldwaser)

Plant species that complete their lifecycle in one season are known as annuals, an example of which is Arabidopsis , or mouse-ear cress. Biennials such as carrots complete their lifecycle in two seasons. In a biennial’s first season, the plant has a vegetative phase, whereas in the next season, it completes its reproductive phase. Commercial growers harvest the carrot roots after the first year of growth, and do not allow the plants to flower. Perennials, such as the magnolia, complete their lifecycle in two years or more.

In another classification based on flowering frequency, monocarpic plants flower only once in their lifetime; examples include bamboo and yucca. During the vegetative period of their life cycle (which may be as long as 120 years in some bamboo species), these plants may reproduce asexually and accumulate a great deal of food material that will be required during their once-in-a-lifetime flowering and setting of seed after fertilization. Soon after flowering, these plants die. Polycarpic plants form flowers many times during their lifetime. Fruit trees, such as apple and orange trees, are polycarpic; they flower every year. Other polycarpic species, such as perennials, flower several times during their life span, but not each year. By this means, the plant does not require all its nutrients to be channelled towards flowering each year.

As is the case with all living organisms, genetics and environmental conditions have a role to play in determining how long a plant will live. Susceptibility to disease, changing environmental conditions, drought, cold, and competition for nutrients are some of the factors that determine the survival of a plant. Plants continue to grow, despite the presence of dead tissue such as cork. Individual parts of plants, such as flowers and leaves, have different rates of survival. In many trees, the older leaves turn yellow and eventually fall from the tree. Leaf fall is triggered by factors such as a decrease in photosynthetic efficiency, due to shading by upper leaves, or oxidative damage incurred as a result of photosynthetic reactions. The components of the part to be shed are recycled by the plant for use in other processes, such as development of seed and storage. This process is known as nutrient recycling.

The aging of a plant and all the associated processes is known as senescence, which is marked by several complex biochemical changes. One of the characteristics of senescence is the breakdown of chloroplasts, which is characterized by the yellowing of leaves. The chloroplasts contain components of photosynthetic machinery such as membranes and proteins. Chloroplasts also contain DNA. The proteins, lipids, and nucleic acids are broken down by specific enzymes into smaller molecules and salvaged by the plant to support the growth of other plant tissues.

The complex pathways of nutrient recycling within a plant are not well understood. Hormones are known to play a role in senescence. Applications of cytokinins and ethylene delay or prevent senescence; in contrast, abscissic acid causes premature onset of senescence.

Sections Summary

Many plants reproduce asexually as well as sexually. In asexual reproduction, part of the parent plant is used to generate a new plant. Grafting, layering, and micropropagation are some methods used for artificial asexual reproduction. The new plant is genetically identical to the parent plant from which the stock has been taken. Asexually reproducing plants thrive well in stable environments.

Plants have different life spans, dependent on species, genotype, and environmental conditions. Parts of the plant, such as regions containing meristematic tissue, continue to grow, while other parts experience programmed cell death. Leaves that are no longer photosynthetically active are shed from the plant as part of senescence, and the nutrients from these leaves are recycled by the plant. Other factors, including the presence of hormones, are known to play a role in delaying senescence.

Review Questions

________ is a useful method of asexual reproduction for propagating hard-to-root plants.

Which of the following is an advantage of asexual reproduction?

• Cuttings taken from an adult plant show increased resistance to diseases.
• Grafted plants can more successfully endure drought.
• When cuttings or buds are taken from an adult plant or plant parts, the resulting plant will grow into an adult faster than a seedling.
• Asexual reproduction takes advantage of a more diverse gene pool.

Plants that flower once in their lifetime are known as ________.

Plant species that complete their lifecycle in one season are known as ________.

Free Response

What are some advantages of asexual reproduction in plants?

Asexual reproduction does not require the expenditure of the plant’s resources and energy that would be involved in producing a flower, attracting pollinators, or dispersing seeds. Asexual reproduction results in plants that are genetically identical to the parent plant, since there is no mixing of male and female gametes, resulting in better survival. The cuttings or buds taken from an adult plant produce progeny that mature faster and are sturdier than a seedling grown from a seed.

Describe natural and artificial methods of asexual reproduction in plants.

Asexual reproduction in plants can take place by natural methods or artificial methods. Natural methods include strategies used by the plant to propagate itself. Artificial methods include grafting, cutting, layering, and micropropagation.

Discuss the life cycles of various plants.

Plant species that complete their life cycle in one season are known as annuals. Biennials complete their life cycle in two seasons. In the first season, the plant has a vegetative phase, whereas in the next season, it completes its reproductive phase. Perennials, such as the magnolia, complete their life cycle in two years or more.

How are plants classified on the basis of flowering frequency?

Monocarpic plants flower only once during their lifetime. During the vegetative period of their lifecycle, these plants accumulate a great deal of food material that will be required during their once-in-a-lifetime flowering and setting of seed after fertilization. Soon after flowering, these plants die. Polycarpic plants flower several times during their life span; therefore, not all nutrients are channelled towards flowering.

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Microbe Notes

Asexual Reproduction: Features, Types, Examples

Reproduction is a biological process of producing offspring of a living organism. It is the basis for continuing life from generation to generation. It is seen in every living organism; from microorganisms to larger organisms including all plants and animals. Based on the number of parents involved, and the formation and fusion of gametes, there are two types of reproduction; sexual reproduction and asexual reproduction.

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Interesting Science Videos

What is Asexual Reproduction?

Asexual reproduction is the type of reproduction where offspring are produced without the fusion of male and female gametes. It is a reproduction process where only one individual makes its progeny without exchanging genetic material with another individual. Generally, it is considered a primitive mode of reproduction and usually occurs in microorganisms, including bacteria, fungi, and protozoa. All of the plants also have the capacity to asexually reproduce. However, only a few plants follow it as a sole mode of reproduction, and others usually show a sexual mode. In the kingdom Animalia , only a few invertebrates show asexual reproduction.

Asexual Reproduction Features

• There is no formation and fusion of male and female gametes. Hence, no male and female are required. 
• Only a single parent is involved in the process.
• There is no exchange in genetic material, hence genetically all the offspring are identical to their parent. 
• There is no chance of variation. Only some mutations may lead to evolutionary changes. Hence, evolutionarily, asexual reproduction is of no importance. 
• The generation time is usually short, and the process occurs in very less time with minimum expense of cellular energy. 
• Offspring mature very quickly and rapidly increase their population. 
• It is usually seen in unicellular organisms. Only a few invertebrates and plants also follow this mode of reproduction.
• Influenced comparatively more than in sexual reproduction by the environmental conditions and nutrition. 

Asexual Reproduction Types

Based on the mode of producing offspring, asexual reproduction is classified into several types, viz.:

Fission simply means division. It is a mode of asexual reproduction where unicellular organisms divide into two or more individuals. It is the most primitive and simple mode of reproduction, shown by unicellular organisms only like bacteria and protozoa. Here the genetic material (nucleus) splits into two or more parts. Then the cytoplasm also divides and new daughter cells are formed; each daughter cell with one nucleus. Depending upon the number of daughter cells produced from fission, it is further classified as binary fission and multiple fission. 

1. Binary Fission

It is the process of asexual reproduction where a single individual divides into two new individuals (daughter cells). Here, first, the DNA (nucleus) is replicated and divided into two, followed by the division of cytoplasm leading to the formation of two daughter cells. It is seen in bacteria, archaebacteria, and protozoa like Amoeba, Leishmania, Plasmodium, Paramecium , etc.  

It is further classified as simple binary fission, longitudinal binary fission, transverse binary fission, and oblique binary fission.

2. Multiple Fission

It is the process of asexual reproduction where a single individual divides into more than two individuals at the same time. In this process, first, the DNA (nucleus) duplicates into several copies (nuclei) (more than two), and each copy (nucleus) is surrounded by cytoplasm leading to the formation of multiple daughter cells.   It is seen in some protozoa like Entamoeba, Plasmodium , etc. some Myxomycetes , and some algae ( Siphonales, Acetabularia, etc.). 

It is a type of asexual reproduction where an outgrowth on the surface of the parent’s body is specialized and separated and developed into a new individual. It is also called “blastogenesis”. In this process, a mature parent produces an outgrowth called ‘bud’. This bud will detach and grow as a new individual (daughter organism).  It is seen in unicellular organisms like yeasts and fungi, certain protozoa, and some bacteria, and multicellular organisms like cnidarians ( Hydra ), jellyfish, flatworms, sea anemones, corals, plants, etc. Budding is further classified as internal and external budding. 

1. Internal Budding (Endodyogeny)

It is the process where two daughter cells are produced within a mother cell, which is then consumed by the daughter cells before their separation. It is usually seen in parasites like Toxoplasma, Frenkelia , etc. 

2. External Budding (Exodyogeny)

In this type, an external outgrowth develops on the surface of a parent organism which will detach on maturation and develop into a new individual. It is seen in yeasts, Hydra, sea anemones, etc.

C. Fragmentation

It is a type of asexual reproduction where the body of a mature organism is broken into several fragments, and each fragment will then subsequently grow into a new complete organism. It is a natural process but usually occurs as a result of some damage to a parent’s body. It is seen in some multicellular animals (like; starfish, Planaria, annelids including polychaetes and oligochaetes, turbellarians, etc.) and plants (like; Spirogyra, Liverwort, etc.). 

D. Regeneration

It is a type of asexual reproduction process where a detached part of an organism develops into a fully developed individual organism. Mostly it is used for restoring damaged body parts (as in many reptiles, amphibians, crayfish, etc.), but some detached parts can grow into a complete individual like in Echinoderms, Hydra , flatworms, etc.).  

E. Vegetative Propagation

It is a type of asexual reproduction shown by plants where a fragment of a plant grows into a new complete plant. The specialized reproductive part of the plant which grows into a new plant is called the vegetative propagule. It includes all the parts of the plant except seeds, fruits, and flowers. It usually occurs via stems, leaves, branches, tuber, roots, etc.  Almost all the plants have the capacity to reproduce by the vegetative propagation method, and plants that can’t produce healthy seeds follow this method as their sole mode of reproduction. Plants like bananas, bamboo, sugarcane, strawberry, rose, tulip, potato, etc. are grown by this method. 

F. Sporogenesis

It is a type of asexual reproduction where haploid spores are produced and developed into new individuals (offspring). It is also called “monogenesis ”. Spores are reproductive cells containing haploid chromosomes which can grow into a mature individual without fertilization. It is seen in many plants, algae, fungi, protozoa, and bacteria. It usually occurs in unfavorable environmental conditions, but in some plants, algae, and fungi, it is a part of their regular lifecycle.

G. Gemmulation

It is a type of asexual reproduction where a new individual is developed from a gemmule. A gemmule is an asexually produced internal cellular mass coated with tough dormant embryonic cells. It is produced in Porifera, freshwater sponges like Spongilla, and marine sponges like sea sponges, Ficulina ficus , etc.  Vegetative totipotent cells called archaeocytes modify and develops into gemmules. These gemmules release out when the sponge body dies, and develop into a new individual when subjected to suitable environmental conditions. 

H. Agamogenesis

It is a type of asexual reproduction where offspring is developed from a female gamete without the involvement of male gametes. In this type, the development of an unfertilized egg occurs leading to the formation of a new individual. It literally means “reproduction without fertilization”, and involves two types; parthenogenesis, and apomixis.

1. Parthenogenesis

It is a type of agamogenesis where an ovum, as a normal reproduction process, develops into an embryo and a mature individual. It is also called “ virgin birth ”. 

It is reported in over 2000 species, mainly in invertebrates (e.g., some bees, wasps, rotifers, few ant species, aphids, water fleas, etc.), and few vertebrates (turkeys, few shark species, some amphibians like frogs and salamanders, some reptiles like rock lizards, Komodo dragons, whiptails, pythons, boas, rattlesnakes, filesnakes, etc.). In plants, it is a part of the apomixis process.

It can be either obligate or facultative parthenogenesis. Some salamanders, geckos, aphids, etc., follow parthenogenesis as the only mode of reproduction. While, parthenogenesis in sharks snakes, Komodo dragons, bees, etc. are facultative types. 

Based on the type of cell division involved during the process, parthenogenesis is of two types;

Apomictic parthenogenesis ; here, egg cells are produced by mitotic division and develop directly into a diploid embryo. This leads to the production of offspring which are full clones of the mother. It is seen in aphids and plants. In plants, it is a component of apomixis. 

Automictic parthenogenesis ; here, egg cells undergo meiotic division before developing into a zygote. This leads to the formation of haploid individuals, but in some, the offspring are reestablished as diploid in several ways. Usually, the egg cell fuses with polar bodies to restore their chromosome number. This causes the production of offspring which are half clones of the mother. It is seen in ants, bees, wasps, amphibians, reptiles, etc.         

2. Apomixis  

It is a type of agamogenesis occurring in plants, where a sporophyte is formed without fertilization. It is seen in plants like hawthorn, blackberries, ferns, rose, meadow grass, dandelions, etc. It is also seen in normally sexually reproducing plants when there is no male plant nearby for pollination.    

Asexual Reproduction in Plants

Several species of plants naturally show asexual reproduction as an obligate or facultative mode of reproduction. Artificially, several economically important plant species are asexually reproduced to rapidly increase their number. Leaves, tubers, bulbs, stems, branches, buds, rhizomes, roots, spores, etc. are used for asexual reproduction in plants. 

A. Natural Methods

• Budding : e.g., in potato, banana, bamboo, sugarcane, apple, pear, cherry, etc., can grow from a bud.
• Vegetative Propagation : e.g. in Bryophyllum , strawberry, sugarcane, roses, banana, sweet potato, yam, onion, garlic, money plant, etc. are cultivated via this method.
• Sporulation: it is seen in fern, moss, liverwort, and algae.
• Fragmentation : it is seen in algae like Spirogyra .
• Apomixis : it is seen in hawthorn, blackberries, ferns, dandelion, etc.

B. Artificial Methods

• Micropropagation and Tissue Culture : these modern techniques include the use of plant cells and/or tissues for the production of a large number of offspring in a laboratory. It is based on the principle of vegetative totipotency of plant cells. Several flowers, ornamental plants, crops like bananas, strawberries, pineapple, etc, are grown by tissue culture technique.  
• Grafting : it is a technique of uniting two different related plants and growing them together as a single plant. It is commonly used in horticulture for cultivating fruits like pear, apple, cherry, almonds, oranges, etc. 
• Layering : it is a technique where a stem/branch of a plant is covered with soil and influenced for root formation. It is a traditional method used for propagating flowers and fruits like strawberry, raspberry, mango, lemon, camellia, etc. 
• Cutting : it is a process where cut pieces of plants are used for propagation. Plants like money plants, sugarcane, coleus, bamboo, rose plant, etc. are cultivated by this method.   

Asexual Reproduction in Animals  

Several species of animals, especially invertebrates, follow the asexual mode of reproduction. Mostly, it is used as a facultative mode of reproduction.  Common types of asexual reproduction in animals include:

• Fission : it is seen in unicellular animals i.e. protozoans like Paramecium, Entamoeba, Leishmania, Plasmodium, Euglena , etc. 
• Fragmentation : it is seen in starfish, Planaria , a few annelids, etc.
• Budding : it is seen in Hydra, Jellyfishes, sea anemones, etc.
• Regeneration : it is seen in crayfish, Echinoderms, Hydra , flatworms, etc.
• Gemmulation : it is seen in sponges. 
• Parthenogenesis : it is seen in wasps, bees, ants, aphids, some sharks, etc.

Asexual Reproduction Advantages

• It helps in rapid reproduction and increases population size. 
• The produced offspring mature within a short time. 
• There is no variation, hence the traits of the parents are preserved and inherited by the offspring. 
• There is comparatively less expense of cellular energy as there is no need for gametogenesis and fertilization. 
• A single parent can produce all the offspring. Hence there is no need for a mate. Also, there is no need for migration for the search for a mate and courtship display. 
• Plants that can’t produce healthy seeds, and require a longer time to sexually mature can be cultivated using the asexual reproduction method. 
• It is not affected by environmental stresses as in sexual reproduction. Also, it occurs as an alternative in case of emergency and harsh environmental conditions. 
• Helps in passing on and replicating the advantageous characteristics in a certain individual inserted by genetic engineering or mutation to a large number of offspring in a short time. 

Asexual Reproduction Disadvantages

• It does not include the exchange of genetic materials hence there is no chance of variation, and it hinders genetic diversity. 
• Harmful traits of parents will continue passing over to the offspring. It will cause the transfer of genetic diseases and other disorders. 
• As there is no evolution, there is the least chance of adaptation to changing environment and a high chance of extinction of the species. 
• There is a rapid increase in population size and intraspecific competition. 
• The offspring mature rapidly and usually have a short lifespan. 

Asexual Reproduction References

• What Is Reproduction? – Definition & Types Of Reproduction (byjus.com)
• Britannica, T. Editors of Encyclopaedia (2020, February 7). budding. Encyclopedia Britannica. https://www.britannica.com/science/budding-reproduction
• What is multiple fission? How does it occur in an organism? Explain briefly. Name one organism which exhibits this type of reproduction. (toppr.com)
• Budding: Definition, Types and Examples (collegedunia.com)
• Budding – Javatpoint
• Endodyogeny of Toxoplasma gondii. A morphological analysis. (cabdirect.org)
• Vegetative Propagation – Meaning, Types, Examples and FAQ (vedantu.com)
• Britannica, T. Editors of Encyclopaedia (2019, February 7). spore. Encyclopedia Britannica. https://www.britannica.com/science/spore-biology
• Regeneration- Types of Regeneration, Regeneration in Hydra (byjus.com)
• Gemmule – Structure formation and Sponge reproduction (byjus.com)
• Gemmules – Formation and Structure of Gemmules and Its Characteristics ( vedantu.com )
• What is the Difference Between Budding and Gemmule Formation | Compare the Difference Between Similar Terms
• Essay on Classification of Asexual Reproduction (preservearticles.com)
• Asexual Reproduction in animals: Features, Types, Advantages & Disadvantages (collegedunia.com)
• Asexual Reproduction in Animals – Examples, Advantages & Disadvantages (byjus.com)
• Two Types Of Reproduction – Asexual Reproduction And Sexual Reproduction (byjus.com)
• Asexual Reproduction – Javatpoint
• Asexual Reproduction – The Definitive Guide | Biology Dictionary
• Agamogenesis – definition of agamogenesis by The Free Dictionary
• Britannica, T. Editors of Encyclopaedia (2019, February 7). apomixis. Encyclopedia Britannica. https://www.britannica.com/science/apomixis
• Parthenogenesis Definition & Meaning – Merriam-Webster
• Parthenogenesis – Types And Significance Of Parthenogenesis (byjus.com)
• Parthenogenesis – an overview | ScienceDirect Topics
• Parthenogenesis Definition and Examples – Biology Online Dictionary
• Examples of plants that make spores and their characteristic (mammothmemory.net)
• Asexual Reproduction in Plants – Definition, Types, Methods, and FAQs (vedantu.com)
• What Is Asexual Reproduction in Plants? Modes, Examples, Diagrams (testbook.com)
• Asexual Reproduction In Plants- Types and Methods (byjus.com)

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Asexual Reproduction: Types and Examples

Reproduction is the process of producing offspring. It is of two types; asexual and sexual reproduction. In sexual reproduction, two egg cells (dual parents) are fused to form a zygote, whereas in asexual reproduction single parent is only required to produce a new offspring.   

This type of asexual reproduction mostly takes place in unicellular organisms. The organisms that undergo asexual reproduction include; bacteria, Archea, plants, fungi, and certain animals. There are different types of asexual reproduction. These include; binary fission, budding, fragmentation, vegetative propagation, sporogenesis, parthenogenesis, and apomixis.

Table of Contents

Types of Asexual Reproduction with Examples

Binary fission.

Types of Binary Fission  

Fragmentation and Regeneration

Regeneration is regenerating or repairing any single part of an organism. Many organisms carry this kind of ability. It is common in lizards (resurgence of tail) and octopuses (regeneration of blood vessels and tails).  

Vegetative Propagation

Vegetative propagation is a type of asexual reproduction common in plants where a plant’s vegetative or non-reproductive part gives rise to new offspring. There are commonly two types of vegetative propagation; natural and artificial.

Sporogenesis

Sporogenesis is the type of asexual reproduction by the production of spores. This type of asexual reproduction occurs in some eukaryotic and prokaryotic organisms like plants , bacteria, fungi, and algae. The reproductive spores forms in the reproductive structure called sporangia which has a sporogenous cell that undergoes cell division to give rise to spores. 

Parthenogenesis

Types of parthenogenesis.

Natural parthenogenesis is of two types; complete and incomplete.

Artificial Parthenogenesis

Apomixis is the process of asexual reproduction in plants where seed formation occurs without meiosis and fertilization. The thus-formed seed then develops into the embryo. It is a substitution for sexual reproduction without involving nucleus and cell fusion. Apomixis is also termed agamospermy. It is classified into the following types: nonrecurrent, recurrent, vegetative, and adventive apomixis.  

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Plant and Animal Reproduction

While all organisms reproduce, not all organisms reproduce the same way. Explore the similar and different ways that plants and animals pass on their genes.

Biology, Genetics

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What Is Reproduction? All organisms reproduce, including plants and animals. The biological process involves an organism producing and/or giving birth to another organism. Just because all organisms reproduce doesn’t mean the methods of reproduction are the same, however. Plants and animals occupy different phylogenetic kingdoms, but they have evolved reproductive systems that overlap and diverge from each other in several ways. Even within the same kingdom, different species may have different methods of reproduction. Types of Reproduction There are two types of reproduction: asexual reproduction and sexual reproduction . The former involves a single parent that produces a genetically identical offspring, whereas the latter involves two parents of the opposite sex, each of whom contributes genetic material to produce a diverse offspring. Different plants and animal can reproduce either asexually or sexually; however, a sexual reproduction is more common among plants than animals. Asexual and sexual reproduction each have benefits and drawbacks. Organisms that reproduce asexually have the advantage of producing several genetically identical offspring quickly and with little energy. On the other hand, the lack of genetic diversity among asexual offspring means they have a lower chance of acclimating to an unstable environment. By contrast, organisms that reproduce sexually have the advantage of producing a genetically diverse offspring, which is able to adapt to its environment. But sexual reproduction comes at a cost, requiring more time and energy to produce an offspring than a sexual reproduction . Fertilization One difference between plant and animal sexual reproduction concerns fertilization . In flowering plants, the fertilization of an egg is achieved by cross- pollination . This process involves an insect like a bee that transfers the pollen grains from the anther , the male part of a flower, to the stigma , the female part of a flower. Once the pollen lands on the stigma , it passes through a long, tube-like structure called a style to reach the ovaries where fertilization takes place. It should be noted that some plants, called hermaphrodites , have male and female parts on the same plant, and are able to self-pollinate. Animals, by contrast, do not depend on third parties like insects in order to mate. As mobile creatures, animals reproduce by physically interacting with each other and often perform various mating rituals in order to woo potential partners. Embryonic Development Despite differences in the fertilization process, the embryonic development of plants and animals is similar. Once a plant egg is fertilized, it starts developing into a multicellular organism in a way similar to an animal embryo. The only major difference between the two is that a plant embryo is contained within a seed, which provides the nutrients it needs to grow, while an animal embryo develops within an egg, outside the organism, or within a uterus, inside the female parent organism. Birth and Germination Plants and animals also differ with respect to how they give birth. Animals exit their mother’s uterus as a newborn or hatch from an egg that has already left the mother’s body. A plant, by contrast, arises by germinating from a seed. The plant releases the seed, which begins to grow once it is in soil and the conditions are right for germination. After the seed has germinated into a plant, it can collect additional nutrients through its roots. Growth Rates The growth rates of plants and animals also vary. Plants have what is called indeterminate growth, meaning there is nearly no limit to how much they can grow. The extent to which a plant can grow is largely determined by its environment. Consequently, plants do not have a size or age that is deemed normal or mature. The growth rate of mammals, such as humans, is also influenced by environmental factors, like nutrition, but animals cease growing once they have reached adulthood. Asexual Reproduction As noted earlier, many plants reproduce asexually. There are a variety of ways plants can reproduce without a partner. For example, some nonflowering plants, such as moss and algae, reproduce by spore formation. These plants form several spores , which break off and grow into separate organisms. Other plants, such as strawberries, are able to reproduce asexually through vegetative propagation , either naturally or artificially. This process involves using a vegetative part of a plant, such as a root or stem, to produce a new plant. Alternative artificial methods, such as grafting , involve combining two plants into one by attaching the top part of a plant, called a scion , to the lower part of a plant, called a rootstock .

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• Biology Article
• Sexual And Asexual Reproduction

Difference between Sexual and Asexual Reproduction

Living organisms, which include humans, animals, plants, algae, fungi and other microorganisms reproduce as a law of nature, a means of ensuring the survival of the species and in the context of evolution. There are two major classifications of reproduction: sexual and asexual reproduction.

Each has its own advantages and disadvantages. Vertebrates, such as humans, exclusively follow sexual reproduction. Many simpler animals such as amoeba follow asexual reproduction.

Explore more:  Reproduction

Let us have a look at the difference between sexual and asexual reproduction.

Asexual Reproduction

Asexual reproduction spans a variety of methods. The simplest single-celled organisms such as archaea, and bacteria, reproduce by binary fission. In this process, the cells simply divide in half, creating a clone of the parent. This method also holds the benefit of being very quick and energy-efficient. For example, bacteria that reproduce by binary fission can give rise to progeny every few hours. Multiple fission also exists, in which an organism splits into more than one offsprings. Certain species of algae and protozoans exhibit multiple fission.

Refer more:   Asexual reproduction

While in multicellular organisms, a similar method called fragmentation is observed. In this process, small pieces break off and grow into new organisms. Another method involves budding , which produces a completely new organism and remains attached to the original body or develops from the original body. A common thread in all this is that the offspring is a direct clone of the parent. The purpose of reproduction, as we’re well aware, is to propagate one’s own genes. Evolutionarily, asexual reproduction is a good bet for the species. It is quick, simple and the genes of the parent will not be diluted by those of another individual. Also, an organism that reproduces asexually can reproduce about twice as fast as one that reproduces sexually.

Sexual Reproduction

Sexual reproduction is the combination of reproductive cells from two individuals to form a third unique offspring. Sexual reproduction produces offspring with a different combination of genes .

One must understand that sexual reproduction is a lot more complex than asexual reproduction. It includes the production of gametes, which have half the number of chromosomes compared to all other cells in the organism. They are produced by the process of meiosis, which produces haploid cells from diploid cells. There occurs crossing over and recombination of genes. Switching from chromosomes to chromosomes  is a good way to ensure that the genes will remain active in a given population. Besides these, factors like gestation period also play an important role in sexual reproduction. The gestation period is the time required for the foetus to fully develop either internally (like in the mother’s womb) or externally (like an egg).

Also Read:   Sexual Reproduction

The differences between sexual and asexual reproduction are as follows:

Interesting Facts about Reproduction

• The record for the longest ever gestation period is held by the elephant which has around 640-660 days as compared to a human’s 280 days.
• The deep-sea male anglerfish bites on to the much larger females and then, the tissues start to fuse until the male fish looks like just a lump of tissue dangling from the female’s body. The male anglerfish receives nutrients and the female fish has access to male sperms to fertilize its eggs.
• Oysters are protandric creatures, this means that they can change from male to female over the course of their lifetime.
• Abiogenesis is a process that still remains a mystery. It speculates how the first-ever life arose from non-living matter such as carbon (Organic compounds.)

Learn more in detail about the differences between sexual and asexual reproduction and other related topics at  BYJU’S Biology

Frequently Asked Questions

How is sexual reproduction different from asexual reproduction.

Sexual reproduction involves the fusion of male and female gametes whereas asexual reproduction does not require male and female individuals and no fusion of gametes takes place.

What are the advantages of asexual reproduction?

Asexual reproduction has the following advantages:

• It requires less energy.
• It can occur in different environments.
• The reproduction process does not require a longer time.
• It requires only a single individual.
• Identical offspring is produced.

What is the advantage of sexual reproduction over asexual reproduction?

Since sexual reproduction requires two individuals, it allows intermingling of genes which is beneficial for the individuals as well as the entire species. The organisms produced by asexual reproduction are genetically identical to each other.

What are the different types of asexual reproduction?

The different types of asexual reproduction include:

• Binary fission
• Fragmentation
• Vegetative Propagation

What is vegetative propagation?

Vegetative propagation is a form of asexual reproduction that occurs in plants in which a new plant can be grown from any vegetative part of the parent plant. For eg., vegetative propagation by the stem in ginger, vegetative propagation by leaves in Bryophyllum.

Put your understanding of this concept to test by answering a few MCQs. Click ‘Start Quiz’ to begin!

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• Basic Genetics

Sexual vs. Asexual Reproduction

Living things use lots of different strategies for producing offspring, but most strategies fall neatly into the categories of either sexual or asexual reproduction. Asexual reproduction generates offspring that are genetically identical to a single parent. In sexual reproduction , two parents contribute genetic information to produce unique offspring.

Sexual and asexual reproduction have advantages and disadvantages—which is why some organisms do both!

Click or tap an organism below . After reading a description, you'll get to vote on whether you think the organism reproduces sexually, asexually, or both. How well do you know your reproductive strategies?

Funding provided by grant 51006109 from the Howard Hughes Medical Institute, Precollege Science Education Initiative for Biomedical Research.

Asexual Reproduction

Asexual Reproduction introduces students to the way in which certain organisms reproduce. Students will learn about different types of asexual reproduction and be able to explain them. They will also discover the process of mitosis. They will also learn about mitosis and how it differs from meiosis in sexual reproduction.

The “Options for Lesson” section contains a number of ideas for additional activities and tasks that you could incorporate into the lesson if you want to or have time to spare. One suggestion is for students to write an essay on cloning and include whether they agree or disagree with cloning humans.

Description

Additional information, what our asexual reproduction lesson plan includes.

Lesson Objectives and Overview: Asexual Reproduction explores the process of mitosis and how certain organisms in the world reproduce. Students will learn a lot of vocabulary related to the lesson and be able to describe different types of asexual reproduction. They will also discover the difference between mitosis and meiosis. This lesson is for students in 5th grade and 6th grade.

Classroom Procedure

Every lesson plan provides you with a classroom procedure page that outlines a step-by-step guide to follow. You do not have to follow the guide exactly. The guide helps you organize the lesson and details when to hand out worksheets. It also lists information in the yellow box that you might find useful. You will find the lesson objectives, state standards, and number of class sessions the lesson should take to complete in this area. In addition, it describes the supplies you will need as well as what and how you need to prepare beforehand. The only supplies you will need to provide apart from the worksheets are scissors.

Options for Lesson

In the “Options for Lesson” section of the classroom procedure page, you will find several suggestions for activities or tasks that you can add into the lesson. For the activity, you might choose to divide students in small groups rather than pairs. You could also split the class into two groups, read the definitions one at a time, and allow each group a guess at the correct term. Another option is for students to research one of the types of asexual reproduction and present information they gather to the class. To incorporate more hands-on activities, you could look into activities involving bread mold, potato plants, spider plants, and so on. Another suggestion is to invite a plant expert to class to talk about how plant reproduce. One more idea is for students to write an essay on cloning and include their views on whether or not they believe it’s okay to clone humans.

Teacher Notes

The paragraph on the teacher notes page gives you some extra information or guidance on what to expect from the lesson. It reminds you that the nature of the subject matter can be tricky depending on the age or maturity of your students. This lesson also contains a lot of vocabulary words that students are likely unfamiliar with for the most part. You can use the blank lines on this page to write out any thoughts you have as you prepare the lesson for your students.

ASEXUAL REPRODUCTION LESSON PLAN CONTENT PAGES

Reproduction.

The Asexual Reproduction lesson plan contains two content pages. Starting off, the lesson describes how every living things reproduces in one way or another. In biology, the definition of reproduction means making a copy or likeness of something so the existence of a species will continue. Without this process, any animal or plant, or other living organism, would die out and no longer exist.

Students will learn that even as they read through these pages, reproduction is happening within their bodies. Skin cells, blood cells, muscle cells, and every other type of cell reproduces continually. As our cells die, they get replaced by new ones through this important process. We don’t even have to do anything to make sure it happens except take care of our bodies.

Generally, people tend to think of parents producing an offspring when they think about reproduction. This applies to a chicken from an, a new flower, or a baby from a human mother. For humans and most plants and animals to produce an offspring, sexual reproduction must take place between two parents. Those parents each contribute one gamete, or sex cell, to the process. While their offspring may look similar to the parents, they will not be exact copies. Sex may be involved, but not always.

On the other hand, there are many other organisms that reproduce from one parent through a process called asexual reproduction. This process does not involve sex, and the offspring will be an exact copy of the parent organism. In other words, a single organism or cell makes an exact copy of itself, kind of like a clone. The DNA and the genes will be exactly the same. However, there are rare occasions in which a mutation can occur. A mutation is a change in the genetic material that passes on from parent to offspring.

Students will then learn a little bit about mitosis and meiosis. Meiosis, which occurs in sexual reproduction, is a process in which half the chromosomes from each of two parents pass onto an offspring. In asexual reproduction, mitosis occurs, which means all the chromosomes copy and create two identical sets of chromosomes. Then the cell nucleus divides into two identical nuclei. Except for sex cells (male sperm and female ova), mitosis is the process that all other cells in the human body use to duplicate.

The lesson provides two images, one to demonstrate meiosis and the other to demonstrate mitosis. Meiosis shows two cells yielding one offspring that is similar but not exactly the same. Mitosis shows one cell yielding two offspring that are exactly the same as the parent. Sexual reproduction is most common in plants and animals while asexual reproduction occurs mostly in single-celled organisms and some plants. In these cases, fertilization does not happen.

Types of Asexual Reproduction

Asexual reproduction is more efficient since only a single parent is necessary for the process to work. The parent simply passes its traits down to the next generation. However, species that rely on this process are less able to adapt to changing environments. This is because there are fewer mutations or changes made to the traits as they pass from parent to offspring.

There are several types of asexual reproduction: binary fission, budding, spores, vegetative, fragmentation, and parthenogenesis. During binary fission, an organism splits into two separate organisms after a period of growth. Examples include sea anemones, coral polyps, and bacteria. With budding, a small part grows until maturity, breaks off, and grows to the same size as the parent. Yeast, hydra, and potatoes are examples of organisms that reproduce this way.

Spores include organisms like mold, algae, and mushrooms. These can also reproduce sexually using meiosis and are capable of reproducing even in poor conditions. Vegetative is the next type during which new plants develop from the roots, stems, or leaves of the parent plant. Geraniums, garlic, strawberries, and daffodils undergo this type of asexual reproduction.

Fragmentation involves the breaking of the body into two parts, leading to regeneration. A separate organism grows from the part. If a sea star loses an arm, for example, the arm grows into a new sea star. Lichens also behave this way. Finally, parthenogenesis occurs when new organisms develop without fertilization. Water fleas, stick insects, some ants, and bees all reproduce this way, but the process is more common in plants.

Cloning is also an example of asexual reproduction because only one parent is needed. Cutting off a piece of a plant and transferring it elsewhere to grow is an example of cloning. A sheep named Dolly was the first mammal to be cloned. She was born in the UK in 1996 and lived for about seven years!

ASEXUAL REPRODUCTION LESSON PLAN WORKSHEETS

The Asexual Reproduction lesson plan includes three worksheets: an activity worksheet, a practice worksheet, and a homework assignment. Each task will help students demonstrate their understanding of the lesson concepts in different ways. Refer to the guide on the classroom procedure page, which outlines when to hand out each worksheet to the class.

MATCHING ACTIVITY WORKSHEET

For the activity, students will work with a partner. The worksheets provide a list of terms and matching definitions. First, students will review the vocabulary and quiz each other. Next, they will cut out all the terms and definitions and mix them up. One partner will then keep track of time as the other partner works to match the all the cards. Students are welcome to use the content pages to check and review their matches. (You can decide not to allow this if you want to make the game a little more difficult.) For each wrong match, the time tracking partner will add 15 seconds. The winner is the person who matches all the terms with the correct definitions in the least amount of time.

MATCH, COMPARE, AND CONTRAST PRACTICE WORKSHEET

The practice worksheet divides into two sections. For the first section, students will review 15 statements. Using the terms in the word bank on the right, students will match the statements to the correct terms. The second section requires students to compare and contrast sexual and asexual reproduction by listing at least three things that are the same and three things that are different.

ASEXUAL REPRODUCTION HOMEWORK ASSIGNMENT

Similar to the practice worksheet, the homework assignment has several sections. Students will first fill in the blanks to 10 sentences. The options to use are in a word bank below the instructions. Next, students will decide which type of asexual reproduction applies to 20 organisms. The options are binary fission (BF), budding (B), spores (S), vegetative (V), fragmentation (F), and parthenogenesis (P). Finally, the last section requires students to explain the difference between mitosis and meiosis in their own words.

Worksheet Answer Keys

The last couple pages of the PDF are answer keys for the practice and homework worksheets. The correct answers are all in red to make it easier for you to compare them to students’ responses. There may be some variation in student answers for the second half of the practice worksheet and the last prompt for the homework assignment. All other responses should match the answer keys. If you choose to administer the lesson pages to your students via PDF, you will need to save a new file that omits these pages. Otherwise, you can simply print out the applicable pages and keep these as reference for yourself when grading assignments.

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• Introduction

Molecular replication

Molecular reproduction.

• Binary fission
• Multiple fission
• Reproduction of organisms
• Life cycles of plants
• Life cycles of animals
• The evolution of reproduction
• The evolution of variation control

reproduction

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• Biology LibreTexts - Reproduction
• Khan Academy - Types of reproduction review
• Milne Library - Reproduction: development and physiology
• Merck Manuals - Professional Version - Conception and Prenatal Development
• National Center for Biotechnology Information - PubMed Central - Research in Reproduction: Challenges, Needs, and Opportunities
• Michigan State University Libraries - An Interactive Introduction to Organismal and Molecular Biology, 2nd ed. - Reproduction
• BCCampus Publishing - Reproduction Methods
• Table Of Contents

reproduction , process by which organisms replicate themselves.

In a general sense reproduction is one of the most important concepts in biology : it means making a copy, a likeness, and thereby providing for the continued existence of species . Although reproduction is often considered solely in terms of the production of offspring in animals and plants, the more general meaning has far greater significance to living organisms. To appreciate this fact, the origin of life and the evolution of organisms must be considered. One of the first characteristics of life that emerged in primeval times must have been the ability of some primitive chemical system to make copies of itself.

At its lowest level, therefore, reproduction is chemical replication. As evolution progressed, cells of successively higher levels of complexity must have arisen, and it was absolutely essential that they had the ability to make likenesses of themselves. In unicellular organisms, the ability of one cell to reproduce itself means the reproduction of a new individual; in multicellular organisms, however, it means growth and regeneration . Multicellular organisms also reproduce in the strict sense of the term—that is, they make copies of themselves in the form of offspring—but they do so in a variety of ways, many involving complex organs and elaborate hormonal mechanisms.

Levels of reproduction

The characteristics that an organism inherits are largely stored in cells as genetic information in very long molecules of deoxyribonucleic acid ( DNA ). In 1953 it was established that DNA molecules consist of two complementary strands, each of which can make copies of the other. The strands are like two sides of a ladder that has been twisted along its length in the shape of a double helix (spring). The rungs, which join the two sides of the ladder, are made up of two terminal bases. There are four bases in DNA : thymine, cytosine, adenine, and guanine. In the middle of each rung a base from one strand of DNA is linked by a hydrogen bond to a base of the other strand. But they can pair only in certain ways: adenine always pairs with thymine, and guanine with cytosine. This is why one strand of DNA is considered complementary to the other.

The double helices duplicate themselves by separating at one place between the two strands and becoming progressively unattached. As one strand separates from the other, each acquires new complementary bases until eventually each strand becomes a new double helix with a new complementary strand to replace the original one. Because adenine always falls in place opposite thymine and guanine opposite cytosine, the process is called a template replication —one strand serves as the mold for the other. It should be added that the steps involving the duplication of DNA do not occur spontaneously; they require catalysts in the form of enzymes that promote the replication process.

The sequence of bases in a DNA molecule serves as a code by which genetic information is stored. Using this code, the DNA synthesizes one strand of ribonucleic acid ( RNA ), a substance that is so similar structurally to DNA that it is also formed by template replication of DNA. RNA serves as a messenger for carrying the genetic code to those places in the cell where proteins are manufactured. The way in which the messenger RNA is translated into specific proteins is a remarkable and complex process. (For more detailed information concerning DNA, RNA, and the genetic code, see the articles nucleic acid and heredity: Chromosomes and genes ). The ability to synthesize enzymes and other proteins enables the organism to make any substance that existed in a previous generation. Proteins are reproduced directly; however, such other substances as carbohydrates, fats, and other organic molecules found in cells are produced by a series of enzyme-controlled chemical reactions, each enzyme being derived originally from DNA through messenger RNA. It is because all of the organic constituents made by organisms are derived ultimately from DNA that molecules in organisms are reproduced exactly by each successive generation.

Cell reproduction

The chemical constituents of cytoplasm (that part of the cell outside the nucleus) are not resynthesized from DNA every time a cell divides. This is because each of the two daughter cells formed during cell division usually inherits about half of the cellular material from the mother cell (see cell: Cell division and growth ), and is important because the presence of essential enzymes enables DNA to replicate even before it has made the enzymes necessary to do so.

Cells of higher organisms contain complex structures, and each time a cell divides the structures must be duplicated . The method of duplication varies for each structure, and in some cases the mechanism is still uncertain. One striking and important phenomenon is the formation of a new membrane . Cell membranes, although they are very thin and appear to have a simple form and structure, contain many enzymes and are sites of great metabolic activity. This applies not only to the membrane that surrounds the cell but to all the membranes within the cell. New membranes, which seem to form rapidly, are indistinguishable from old ones.

Thus, the formation of a new cell involves the further synthesis of many constituents that were present in the parent cell. This means that all of the information and materials necessary for a cell to reproduce itself must be supplied by the cellular constituents and the DNA inherited from the parent cell.