Asexual reproduction

Last updated

Asexual reproduction in liverworts: a caducous phylloid germinating Caduco.jpg
Asexual reproduction in liverworts: a caducous phylloid germinating

Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the full set of genes of their single parent and thus the newly created individual is genetically and physically similar to the parent or an exact clone of the parent. Asexual reproduction is the primary form of reproduction for single-celled organisms such as archaea and bacteria. Many eukaryotic organisms including plants, animals, and fungi can also reproduce asexually. [1] In vertebrates, the most common form of asexual reproduction is parthenogenesis, which is typically used as an alternative to sexual reproduction in times when reproductive opportunities are limited. Some monitor lizards, including Komodo dragons, can reproduce asexually. [2]

Contents

While all prokaryotes reproduce without the formation and fusion of gametes, mechanisms for lateral gene transfer such as conjugation, transformation and transduction can be likened to sexual reproduction in the sense of genetic recombination in meiosis. [3] [4]

Types of asexual reproduction

Fission

Prokaryotes (Archaea and Bacteria) reproduce asexually through binary fission, in which the parent organism divides in two to produce two genetically identical daughter organisms. Eukaryotes (such as protists and unicellular fungi) may reproduce in a functionally similar manner by mitosis; most of these are also capable of sexual reproduction.

Multiple fission at the cellular level occurs in many protists, e.g. sporozoans and algae. The nucleus of the parent cell divides several times by mitosis, producing several nuclei. The cytoplasm then separates, creating multiple daughter cells. [5] [6] [7]

In apicomplexans, multiple fission, or schizogony appears either as merogony, sporogony or gametogony. Merogony results in merozoites, which are multiple daughter cells, that originate within the same cell membrane, [8] [9] sporogony results in sporozoites, and gametogony results in microgametes.

Budding

The yeast Saccharomyces cerevisiae reproducing by budding S cerevisiae under DIC microscopy.jpg
The yeast Saccharomyces cerevisiae reproducing by budding

Some cells divide by budding (for example baker's yeast), resulting in a "mother" and a "daughter" cell that is initially smaller than the parent. Budding is also known on a multicellular level; an animal example is the hydra, [10] which reproduces by budding. The buds grow into fully matured individuals which eventually break away from the parent organism.

Internal budding is a process of asexual reproduction, favoured by parasites such as Toxoplasma gondii . It involves an unusual process in which two (endodyogeny) or more (endopolygeny) daughter cells are produced inside a mother cell, which is then consumed by the offspring prior to their separation. [11]

Also, budding (external or internal) occurs in some worms like Taenia or Echinococcus ; these worms produce cysts and then produce (invaginated or evaginated) protoscolex with budding.

Vegetative propagation

Vegetative plantlets of mother-of-thousands, Bryophyllum daigremontianum (Kalanchoe daigremontiana) Bryophyllum daigremontianum nahaufnahme1.jpg
Vegetative plantlets of mother-of-thousands, Bryophyllum daigremontianum (Kalanchoe daigremontiana)

Vegetative propagation is a type of asexual reproduction found in plants where new individuals are formed without the production of seeds or spores and thus without syngamy or meiosis. [12] Examples of vegetative reproduction include the formation of miniaturized plants called plantlets on specialized leaves, for example in kalanchoe ( Bryophyllum daigremontianum ) and many produce new plants from rhizomes or stolon (for example in strawberry). Some plants reproduce by forming bulbs or tubers, for example tulip bulbs and Dahlia tubers. In these examples, all the individuals are clones, and the clonal population may cover a large area. [13]

Spore formation

Many multicellular organisms produce spores during their biological life cycle in a process called sporogenesis. Exceptions are animals and some protists, which undergo meiosis immediately followed by fertilization. Plants and many algae on the other hand undergo sporic meiosis where meiosis leads to the formation of haploid spores rather than gametes. These spores grow into multicellular individuals called gametophytes, without a fertilization event. These haploid individuals produce gametes through mitosis. Meiosis and gamete formation therefore occur in separate multicellular generations or "phases" of the life cycle, referred to as alternation of generations. Since sexual reproduction is often more narrowly defined as the fusion of gametes (fertilization), spore formation in plant sporophytes and algae might be considered a form of asexual reproduction (agamogenesis) despite being the result of meiosis and undergoing a reduction in ploidy. However, both events (spore formation and fertilization) are necessary to complete sexual reproduction in the plant life cycle.

Fungi and some algae can also utilize true asexual spore formation, which involves mitosis giving rise to reproductive cells called mitospores that develop into a new organism after dispersal. This method of reproduction is found for example in conidial fungi and the red algae Polysiphonia, and involves sporogenesis without meiosis. Thus the chromosome number of the spore cell is the same as that of the parent producing the spores. However, mitotic sporogenesis is an exception and most spores, such as those of plants and many algae, are produced by meiosis. [14] [15] [16]

Fragmentation

Linckia guildingi "comet", a starfish regrowing from a single arm Tu - Linckia guildingi cropped.jpg
Linckia guildingi "comet", a starfish regrowing from a single arm

Fragmentation is a form of asexual reproduction where a new organism grows from a fragment of the parent. Each fragment develops into a mature, fully grown individual. Fragmentation is seen in many organisms. Animals that reproduce asexually include planarians, many annelid worms including polychaetes [17] and some oligochaetes, [17] turbellarians and sea stars. Many fungi and plants reproduce asexually. Some plants have specialized structures for reproduction via fragmentation, such as gemmae in mosses and liverworts. Most lichens, which are a symbiotic union of a fungus and photosynthetic algae or cyanobacteria, reproduce through fragmentation to ensure that new individuals contain both symbionts. These fragments can take the form of soredia, dust-like particles consisting of fungal hyphae wrapped around photobiont cells.

Clonal Fragmentation in multicellular or colonial organisms is a form of asexual reproduction or cloning where an organism is split into fragments. Each of these fragments develop into mature, fully grown individuals that are clones of the original organism. In echinoderms, this method of reproduction is usually known as fissiparity. [18] Due to many environmental and epigenetic differences, clones originating from the same ancestor might actually be genetically and epigenetically different. [19]

Agamogenesis

Agamogenesis is any form of reproduction that does not involve a male gamete. Examples are parthenogenesis and apomixis.

Parthenogenesis

Parthenogenesis is a form of agamogenesis in which an unfertilized egg develops into a new individual. It has been documented in over 2,000 species. [20] Parthenogenesis occurs in the wild in many invertebrates (e.g. water fleas, rotifers, aphids, stick insects, some ants, bees and parasitic wasps) and vertebrates (mostly reptiles, amphibians, and fish). It has also been documented in domestic birds and in genetically altered lab mice. [21] [22] Plants can engage in parthenogenesis as well through a process called apomixis. However this process is considered by many to not be an independent reproduction method, but instead a breakdown of the mechanisms behind sexual reproduction. [23] Parthenogenetic organisms can be split into two main categories: facultative and obligate.

Facultative parthenogenesis
Zebra shark Zebra Shark.jpg
Zebra shark

In facultative parthenogenesis, females can reproduce both sexually and asexually. [20] Because of the many advantages of sexual reproduction, most facultative parthenotes only reproduce asexually when forced to. This typically occurs in instances when finding a mate becomes difficult. For example, female zebra sharks will reproduce asexually if they are unable to find a mate in their ocean habitats. [2]

Parthenogenesis was previously believed to rarely occur in vertebrates, and only be possible in very small animals. However, it has been discovered in many more species in recent years. Today, the largest species that has been documented reproducing parthenogenically is the Komodo dragon at 10 feet long and over 300 pounds. [24] [25]

Aphid giving birth to live young from an unfertilized egg Aphid-giving-birth.jpg
Aphid giving birth to live young from an unfertilized egg

Heterogony is a form of facultative parthenogenesis where females alternate between sexual and asexual reproduction at regular intervals (see Alternation between sexual and asexual reproduction). Aphids are one group of organism that engages in this type of reproduction. They use asexual reproduction to reproduce quickly and create winged offspring that can colonize new plants and reproduce sexually in the fall to lay eggs for the next season. [26] However, some aphid species are obligate parthenotes. [27]

Obligate parthenogenesis
Desert grassland whiptail lizard females reproduce by obligate parthenogenesis. DesertGrasslandWhiptailLizard AspidoscelisUniparens56.jpg
Desert grassland whiptail lizard females reproduce by obligate parthenogenesis.

In obligate parthenogenesis, females only reproduce asexually. [20] One example of this is the desert grassland whiptail lizard, a hybrid of two other species. Typically hybrids are infertile but through parthenogenesis this species has been able to develop stable populations. [28]

Gynogenesis is a form of obligate parthenogenesis where a sperm cell is used to initiate reproduction. However, the sperm's genes never get incorporated into the egg cell. The best known example of this is the Amazon molly. Because they are obligate parthenotes, there are no males in their species so they depend on males from a closely related species (the Sailfin molly) for sperm. [29]

Apomixis and nucellar embryony

Apomixis in plants is the formation of a new sporophyte without fertilization. It is important in ferns and in flowering plants, but is very rare in other seed plants. In flowering plants, the term "apomixis" is now most often used for agamospermy, the formation of seeds without fertilization, but was once used to include vegetative reproduction. An example of an apomictic plant would be the triploid European dandelion. Apomixis mainly occurs in two forms: In gametophytic apomixis, the embryo arises from an unfertilized egg within a diploid embryo sac that was formed without completing meiosis. In nucellar embryony, the embryo is formed from the diploid nucellus tissue surrounding the embryo sac. Nucellar embryony occurs in some citrus seeds. Male apomixis can occur in rare cases, such as in the Saharan Cypress Cupressus dupreziana , where the genetic material of the embryo is derived entirely from pollen. [30] [31] [32]

Androgenesis

Androgenesis occurs when a zygote is produced with only paternal nuclear genes. During standard sexual reproduction, one female and one male parent each produce haploid gametes (such as a sperm or egg cell, each containing only a single set of chromosomes), which recombine to create offspring with genetic material from both parents. However, in androgenesis, there is no recombination of maternal and paternal chromosomes, and only the paternal chromosomes are passed down to the offspring (the inverse of this is gynogenesis, where only the maternal chromosomes are inherited, which is more common than androgenesis). [33] The offspring produced in androgenesis will still have maternally inherited mitochondria, as is the case with most sexually reproducing species. Androgenesis occurs in nature in many invertebrates (for example, clams, [34] stick insects, [35] some ants, [36] bees, [37] flies [38] and parasitic wasps [37] ) and vertebrates (mainly amphibians [39] and fish [37] [40] ). The androgenesis has also been seen in genetically modified laboratory mice. [41]

One of two things can occur to produce offspring with exclusively paternal genetic material: the maternal nuclear genome can be eliminated from the zygote, or the female can produce an egg with no nucleus, resulting in an embryo developing with only the genome of the male gamete.

Male apomixis

Other type of androgenesis is the male apomixis or paternal apomixis is a reproductive process in which a plant develops from a sperm cell (male gamete) without the participation of a female cell (ovum). In this process, the zygote is formed solely with genetic material from the father, resulting in offspring genetically identical to the male organism. [42] [43] [44] This has been noted in many plants like Nicotiana , Capsicum frutescens , Cicer arietinum , Poa arachnifera , Solanum verrucosum , Phaeophyceae , [45] Pripsacum dactyloides , Zea mays , [37] and occurs as the regular reproductive method in Cupressus dupreziana . [42] This contrasts with the more common apomixis, where development occurs without fertilization, but with genetic material only from the mother.

There are also clonal species that reproduce through vegetative reproduction like Lomatia tasmanica [46] [47] and Pando, [48] where the genetic material is exclusively male.

Other species where androgenesis has been observed naturally are the stick insects Bacillus rossius and Bassillus Grandii , [35] the little fire ant Wasmannia auropunctata , [36] Vollenhovia emeryi , [37] Paratrechina longicornis , [37] occasionally in Apis mellifera , [37] the Hypseleotris carp gudgeons, [37] the parasitoid Venturia canescens , [37] and occasionally in fruit flies Drosophila melanogaster carrying a specific mutant allele. [38] It has also been induced in many crops and fish via irradiation of an egg cell to destroy the maternal nuclear genome. [49]

Obligate androgenesis

Obligate androgenesis is the process in which males [34] are capable of producing both eggs and sperm, however, the eggs have no genetic contribution and the offspring come only from the sperm, which allows these individuals to self-fertilize and produce clonal offspring without the need for females. They are also capable of interbreeding with sexual and other androgenetic lineages in a phenomenon known as "egg parasitism." This method of reproduction has been found in several species of the clam genus Corbicula , [34] many plants like, Cupressus dupreziana , [50] Lomatia tasmanica , [46] [47] Pando [48] and recently in the fish Squalius alburnoides . [40]

Other species where androgenesis has been observed naturally are the stick insects Bacillus rossius and Bassillus Grandii , [35] the little fire ant Wasmannia auropunctata , [36] Vollenhovia emeryi , [37] Paratrechina longicornis , [37] occasionally in Apis mellifera , [37] the Hypseleotris carp gudgeons, [37] the parasitoid Venturia canescens , [37] and occasionally in fruit flies Drosophila melanogaster carrying a specific mutant allele. [38] It has also been induced in many crops and fish via irradiation of an egg cell to destroy the maternal nuclear genome. [49]

Alternation between sexual and asexual reproduction

Aphid populations are often entirely female during the summer, with sexual reproduction only to produce eggs for overwintering. Soybeanaphidlifecycle.gif
Aphid populations are often entirely female during the summer, with sexual reproduction only to produce eggs for overwintering.

Some species can alternate between sexual and asexual strategies, an ability known as heterogamy , depending on many conditions. Alternation is observed in several rotifer species (cyclical parthenogenesis e.g. in Brachionus species) and a few types of insects.

One example of this is aphids which can engage in heterogony. In this system, females are born pregnant and produce only female offspring. This cycle allows them to reproduce very quickly. However, most species reproduce sexually once a year. This switch is triggered by environmental changes in the fall and causes females to develop eggs instead of embryos. This dynamic reproductive cycle allows them to produce specialized offspring with polyphenism, a type of polymorphism where different phenotypes have evolved to carry out specific tasks. [26]

The cape bee Apis mellifera subsp. capensis can reproduce asexually through a process called thelytoky. The freshwater crustacean Daphnia reproduces by parthenogenesis in the spring to rapidly populate ponds, then switches to sexual reproduction as the intensity of competition and predation increases. Monogonont rotifers of the genus Brachionus reproduce via cyclical parthenogenesis: at low population densities females produce asexually and at higher densities a chemical cue accumulates and induces the transition to sexual reproduction. Many protists and fungi alternate between sexual and asexual reproduction. A few species of amphibians, reptiles, and birds have a similar ability.[ which? ][ which? ]

The slime mold Dictyostelium undergoes binary fission (mitosis) as single-celled amoebae under favorable conditions. However, when conditions turn unfavorable, the cells aggregate and follow one of two different developmental pathways, depending on conditions. In the social pathway, they form a multi-cellular slug which then forms a fruiting body with asexually generated spores. In the sexual pathway, two cells fuse to form a giant cell that develops into a large cyst. When this macrocyst germinates, it releases hundreds of amoebic cells that are the product of meiotic recombination between the original two cells. [51]

The hyphae of the common mold ( Rhizopus ) are capable of producing both mitotic as well as meiotic spores. Many algae similarly switch between sexual and asexual reproduction. [52] A number of plants use both sexual and asexual means to produce new plants, some species alter their primary modes of reproduction from sexual to asexual under varying environmental conditions. [53]

Inheritance in asexual species

In the rotifer Brachionus calyciflorus asexual reproduction (obligate parthenogenesis) can be inherited by a recessive allele, which leads to loss of sexual reproduction in homozygous offspring. [54] [55]
Inheritance of asexual reproduction by a single recessive locus has also been found in the parasitoid wasp Lysiphlebus fabarum. [56]

Examples in animals

Asexual reproduction is found in nearly half of the animal phyla. [57] Parthenogenesis occurs in the hammerhead shark [58] and the blacktip shark. [59] [60] In both cases, the sharks had reached sexual maturity in captivity in the absence of males, and in both cases the offspring were shown to be genetically identical to the mothers. The New Mexico whiptail is another example.

Some reptiles use the ZW sex-determination system, which produces either males (with ZZ sex chromosomes) or females (with ZW or WW sex chromosomes). Until 2010, it was thought that the ZW chromosome system used by reptiles was incapable of producing viable WW offspring, but a (ZW) female boa constrictor was discovered to have produced viable female offspring with WW chromosomes. [61] The female boa could have chosen any number of male partners (and had successfully in the past) but on this occasion she reproduced asexually, creating 22 female babies with WW sex-chromosomes.

Polyembryony is a widespread form of asexual reproduction in animals, whereby the fertilized egg or a later stage of embryonic development splits to form genetically identical clones. Within animals, this phenomenon has been best studied in the parasitic Hymenoptera. In the nine-banded armadillos, this process is obligatory and usually gives rise to genetically identical quadruplets. In other mammals, monozygotic twinning has no apparent genetic basis, though its occurrence is common. There are at least 10 million identical human twins and triplets in the world today.

Bdelloid rotifers reproduce exclusively asexually, and all individuals in the class Bdelloidea are females. Asexuality evolved in these animals millions of years ago and has persisted since. There is evidence to suggest that asexual reproduction has allowed the animals to evolve new proteins through the Meselson effect that have allowed them to survive better in periods of dehydration. [62] Bdelloid rotifers are extraordinarily resistant to damage from ionizing radiation due to the same DNA-preserving adaptations used to survive dormancy. [63] These adaptations include an extremely efficient mechanism for repairing DNA double-strand breaks. [64] This repair mechanism was studied in two Bdelloidea species, Adineta vaga, [64] and Philodina roseola. [65] and appears to involve mitotic recombination between homologous DNA regions within each species.

Molecular evidence strongly suggests that several species of the stick insect genus Timema have used only asexual (parthenogenetic) reproduction for millions of years, the longest period known for any insect. [66] Similar findings suggest that the mite species Oppiella nova may have reproduced entirely asexually for millions of years. [67]

In the grass thrips genus Aptinothrips there have been several transitions to asexuality, likely due to different causes. [68]

Adaptive significance of asexual reproduction

A complete lack of sexual reproduction is relatively rare among multicellular organisms, particularly animals. It is not entirely understood why the ability to reproduce sexually is so common among them. Current hypotheses [69] suggest that asexual reproduction may have short term benefits when rapid population growth is important or in stable environments, while sexual reproduction offers a net advantage by allowing more rapid generation of genetic diversity, allowing adaptation to changing environments. Developmental constraints [70] may underlie why few animals have relinquished sexual reproduction completely in their life-cycles. Almost all asexual modes of reproduction maintain meiosis either in a modified form or as an alternative pathway. [71] Facultatively apomictic plants increase frequencies of sexuality relative to apomixis after abiotic stress. [71] Another constraint on switching from sexual to asexual reproduction would be the concomitant loss of meiosis and the protective recombinational repair of DNA damage afforded as one function of meiosis. [72] [73]

See also

Related Research Articles

<span class="mw-page-title-main">Gamete</span> Haploid sex cell

A gamete is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. The name gamete was introduced by the German cytologist Eduard Strasburger in 1878.

<span class="mw-page-title-main">Meiosis</span> Cell division producing haploid gametes

Meiosis (; from Ancient Greek μείωσις 'lessening', is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, the sperm or egg cells. It involves two rounds of division that ultimately result in four cells, each with only one copy of each chromosome. Additionally, prior to the division, genetic material from the paternal and maternal copies of each chromosome is crossed over, creating new combinations of code on each chromosome. Later on, during fertilisation, the haploid cells produced by meiosis from a male and a female will fuse to create a zygote, a cell with two copies of each chromosome again.

<span class="mw-page-title-main">Reproduction</span> Biological process by which new organisms are generated from one or more parent organisms

Reproduction is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. There are two forms of reproduction: asexual and sexual.

<span class="mw-page-title-main">Fertilisation</span> Union of gametes of opposite sexes during the process of sexual reproduction to form a zygote

Fertilisation or fertilization, also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a zygote and initiate its development into a new individual organism or offspring. While processes such as insemination or pollination, which happen before the fusion of gametes, are also sometimes informally referred to as fertilisation, these are technically separate processes. The cycle of fertilisation and development of new individuals is called sexual reproduction. During double fertilisation in angiosperms, the haploid male gamete combines with two haploid polar nuclei to form a triploid primary endosperm nucleus by the process of vegetative fertilisation.

<span class="mw-page-title-main">Apomixis</span> Replacement of the normal sexual reproduction by asexual reproduction, without fertilization

In botany, apomixis is asexual development of seed or embryo without fertilization. However, other definitions include replacement of the seed by a plantlet or replacement of the flower by bulbils.

<span class="mw-page-title-main">Gametogenesis</span> Biological process

Gametogenesis is a biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes. Depending on the biological life cycle of the organism, gametogenesis occurs by meiotic division of diploid gametocytes into various gametes, or by mitosis. For example, plants produce gametes through mitosis in gametophytes. The gametophytes grow from haploid spores after sporic meiosis. The existence of a multicellular, haploid phase in the life cycle between meiosis and gametogenesis is also referred to as alternation of generations.

<span class="mw-page-title-main">Biological life cycle</span> Series of stages of an organism

In biology, a biological life cycle is a series of stages of the life of an organism, that begins as a zygote, often in an egg, and concludes as an adult that reproduces, producing an offspring in the form of a new zygote which then itself goes through the same series of stages, the process repeating in a cyclic fashion.

<span class="mw-page-title-main">Germline</span> Population of a multicellular organisms cells that pass on their genetic material to the progeny

In biology and genetics, the germline is the population of a multicellular organism's cells that develop into germ cells. In other words, they are the cells that form gametes, which can come together to form a zygote. They differentiate in the gonads from primordial germ cells into gametogonia, which develop into gametocytes, which develop into the final gametes. This process is known as gametogenesis.

<span class="mw-page-title-main">Evolution of sexual reproduction</span>

Evolution of sexual reproduction describes how sexually reproducing animals, plants, fungi and protists could have evolved from a common ancestor that was a single-celled eukaryotic species. Sexual reproduction is widespread in eukaryotes, though a few eukaryotic species have secondarily lost the ability to reproduce sexually, such as Bdelloidea, and some plants and animals routinely reproduce asexually without entirely having lost sex. The evolution of sexual reproduction contains two related yet distinct themes: its origin and its maintenance. Bacteria and Archaea (prokaryotes) have processes that can transfer DNA from one cell to another, but it is unclear if these processes are evolutionarily related to sexual reproduction in Eukaryotes. In eukaryotes, true sexual reproduction by meiosis and cell fusion is thought to have arisen in the last eukaryotic common ancestor, possibly via several processes of varying success, and then to have persisted.

<span class="mw-page-title-main">Thelytoky</span> Type of parthenogenesis in which females are produced from unfertilized eggs

Thelytoky is a type of parthenogenesis and is the absence of mating and subsequent production of all female diploid offspring as for example in aphids. Thelytokous parthenogenesis is rare among animals and reported in about 1,500 species, about 1 in 1000 of described animal species, according to a 1984 study. It is more common in invertebrates, like arthropods, but it can occur in vertebrates, including salamanders, fish, and reptiles such as some whiptail lizards.

Plant reproduction is the production of new offspring in plants, which can be accomplished by sexual or asexual reproduction. Sexual reproduction produces offspring by the fusion of gametes, resulting in offspring genetically different from either parent. Asexual reproduction produces new individuals without the fusion of gametes, resulting in clonal plants that are genetically identical to the parent plant and each other, unless mutations occur.

<span class="mw-page-title-main">Parthenogenesis</span> Asexual reproduction without fertilization

Parthenogenesis is a natural form of asexual reproduction in which the embryo develops directly from an egg without need for fertilization. In animals, parthenogenesis means development of an embryo from an unfertilized egg cell. In plants, parthenogenesis is a component process of apomixis. In algae, parthenogenesis can mean the development of an embryo from either an individual sperm or an individual egg.

In botany, a zoid or zoïd is a reproductive cell that possesses one or more flagella, and is capable of independent movement. Zoid can refer to either an asexually reproductive spore or a sexually reproductive gamete. In sexually reproductive gametes, zoids can be either male or female depending on the species. For example, some brown alga (Phaeophyceae) reproduce by producing multi-flagellated male and female gametes that recombine to form the diploid sporangia. Zoids are primarily found in some protists, diatoms, green alga, brown alga, non-vascular plants, and a few vascular plants. The most common classification group that produces zoids is the heterokonts or stramenopiles. These include green alga, brown alga, oomycetes, and some protists. The term is generally not used to describe motile, flagellated sperm found in animals. Zoid is also commonly confused for zooid which is a single organism that is part of a colonial animal.

<span class="mw-page-title-main">Sexual reproduction</span> Biological process

Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete with a single set of chromosomes combines with another gamete to produce a zygote that develops into an organism composed of cells with two sets of chromosomes (diploid). This is typical in animals, though the number of chromosome sets and how that number changes in sexual reproduction varies, especially among plants, fungi, and other eukaryotes.

<span class="mw-page-title-main">Automixis</span> Fusion of nuclei or gametes from same individual

Automixis is the fusion of nuclei or gametes derived from the same individual. The term covers several reproductive mechanisms, some of which are parthenogenetic.

Parthenogenesis is a mode of asexual reproduction in which offspring are produced by females without the genetic contribution of a male. Among all the sexual vertebrates, the only examples of true parthenogenesis, in which all-female populations reproduce without the involvement of males, are found in squamate reptiles. There are about 50 species of lizard and 1 species of snake that reproduce solely through parthenogenesis. It is unknown how many sexually reproducing species are also capable of parthenogenesis in the absence of males, but recent research has revealed that this ability is widespread among squamates.

Autogamy or self-fertilization refers to the fusion of two gametes that come from one individual. Autogamy is predominantly observed in the form of self-pollination, a reproductive mechanism employed by many flowering plants. However, species of protists have also been observed using autogamy as a means of reproduction. Flowering plants engage in autogamy regularly, while the protists that engage in autogamy only do so in stressful environments.

Gynogenesis, a form of parthenogenesis, is a system of asexual reproduction that requires the presence of sperm without the actual contribution of its DNA for completion. The paternal DNA dissolves or is destroyed before it can fuse with the egg. The egg cell of the organism is able to develop, unfertilized, into an adult using only maternal genetic material. Gynogenesis is often termed "sperm parasitism" in reference to the somewhat pointless role of male gametes. Gynogenetic species, "gynogens" for short, are unisexual, meaning they must mate with males from a closely related bisexual species that normally reproduces sexually.

Androgenesis is a system of asexual reproduction that requires the presence of eggs and occurs when a zygote is produced with only paternal nuclear genes. During standard sexual reproduction, one female parent and one male parent each produce haploid gametes, which recombine to create offspring with genetic material from both parents. However, in androgenesis, there is no recombination of maternal and paternal chromosomes, and only the paternal chromosomes are passed down to the offspring.. The offspring produced in androgenesis will still have maternally inherited mitochondria, as is the case with most sexually reproducing species.

References

  1. ↑ Engelstädter, Jan (June 2017). "Asexual but Not Clonal: Evolutionary Processes in Automictic Populations". Genetics. 206 (2): 993–1009. doi:10.1534/genetics.116.196873. PMC   5499200 . PMID   28381586.
  2. 1 2 Dudgeon, Christine L.; Coulton, Laura; Bone, Ren; Ovenden, Jennifer R.; Thomas, Severine (16 January 2017). "Switch from sexual to parthenogenetic reproduction in a zebra shark". Scientific Reports. 7 (1): 40537. Bibcode:2017NatSR...740537D. doi:10.1038/srep40537. PMC   5238396 . PMID   28091617.
  3. ↑ Narra, H. P.; Ochman, H. (2006). "Of what use is sex to bacteria?". Current Biology. 16 (17): R705–710. Bibcode:2006CBio...16.R705N. doi: 10.1016/j.cub.2006.08.024 . PMID   16950097.
  4. ↑ Bryner, Jeanna (20 December 2006). "Female Komodo Dragon Has Virgin Births". Live Science.
  5. ↑ "Cell reproduction". Encyclopædia Britannica.
  6. ↑ Britannica Educational Publishing (2011). Fungi, Algae, and Protists. The Rosen Publishing Group. ISBN   978-1-61530-463-9.
  7. ↑ P.Puranik; Asha Bhate (2007). Animal Forms And Functions: Invertebrata. Sarup & Sons. ISBN   978-81-7625-791-6.
  8. ↑ Margulis, Lynn; McKhann, Heather I.; Olendzenski, Lorraine (2001). Illustrated glossary of protoctista: vocabulary of the algae, apicomplexa, ciliates, foraminifera, microspora, water molds, slime molds, and the other protoctists. Jones & Bartlett learn. ISBN   978-0-86720-081-2.
  9. ↑ Yoshinori Tanada; Harry K. Kaya (1993). Insect pathology. Gulf Professional Publishing. ISBN   978-0-12-683255-6.
  10. ↑ Leeuwenhoek, Antoni Van (February 1703). "IV. Part of a letter from Mr Antony van Leeuwenhoek, F. R. S. concerning green weeds growing in water, and some animalcula found about them". Philosophical Transactions of the Royal Society of London. 23 (283): 1304–1311. doi:10.1098/rstl.1702.0042.
  11. ↑ Smyth, James Desmond; Wakelin, Derek (1994). Introduction to animal parasitology (3 ed.). Cambridge University Press. pp. 101–102. ISBN   978-0-521-42811-8.
  12. ↑ "Asexual Reproduction". Ucmp.berkeley.edu. Retrieved 13 August 2010.
  13. ↑ "Celebrating Wildflowers – Fading Gold – How Aspens Grow". Fs.fed.us. 11 May 2010. Archived from the original on 23 September 2010.
  14. ↑ "Plant." Britannica Academic, Encyclopædia Britannica, 15 Jun. 2021. Accessed 20 Jan. 2022.
  15. ↑ Card, V. (2016). Algae. In M. S. Hill (Ed.), Biology (2nd ed., Vol. 1, pp. 21–23). Macmillan Reference USA.
  16. ↑ "Fungus." Britannica Academic, Encyclopædia Britannica, 4 Oct. 2018. Accessed 20 Jan. 2022.
  17. 1 2 Ruppert, E. E.; Fox, R. S.; Barnes, R. D. (2004). "Annelida". Invertebrate Zoology (7 ed.). Brooks / Cole. pp.  434–441. ISBN   978-0-03-025982-1.
  18. ↑ Sköld, Helen Nilsson; Obst, Matthias; Sköld, Mattias; Åkesson, Bertil (2009). "Stem Cells in Asexual Reproduction of Marine Invertebrates". In Baruch Rinkevich; Valeria Matranga (eds.). Stem Cells in Marine Organisms. Springer. p. 125. ISBN   978-90-481-2766-5.
  19. ↑ Neuhof, Moran; Levin, Michael; Rechavi, Oded (26 August 2016). "Vertically and horizontally-transmitted memories – the fading boundaries between regeneration and inheritance in planaria". Biology Open. 5 (9): 1177–1188. doi:10.1242/bio.020149. PMC   5051648 . PMID   27565761.
  20. 1 2 3 "parthenogenesis | Definition, Types, & Facts". Encyclopedia Britannica. Retrieved 3 December 2020.
  21. ↑ Kono, Tomohiro; Obata, Yayoi; Wu, Quiong; Niwa, Katsutoshi; Ono, Yukiko; Yamamoto, Yuji; Park, Eun Sung; Seo, Jeong-Sun; Ogawa, Hidehiko (April 2004). "Birth of parthenogenetic mice that can develop to adulthood". Nature. 428 (6985): 860–864. doi:10.1038/nature02402. PMID   15103378.
  22. ↑ Ramachandran, R; McDaniel, C D (June 2018). "Parthenogenesis in birds: a review". Reproduction. 155 (6): R245–R257. doi: 10.1530/REP-17-0728 . PMID   29559496.
  23. ↑ Ozias-Akins, Peggy; Conner, Joann A. (2012). "Regulation of apomixis". Plant Biotechnology and Agriculture. pp. 243–254. doi:10.1016/B978-0-12-381466-1.00016-X. ISBN   978-0-12-381466-1.
  24. ↑ Yam, Philip. "Strange but True: Komodo Dragons Show that "Virgin Births" Are Possible". Scientific American. Retrieved 13 December 2020.
  25. ↑ "Komodo dragon". Animals. 10 September 2010. Archived from the original on 17 October 2016. Retrieved 13 December 2020.
  26. 1 2 Stern, David L. (June 2008). "Aphids". Current Biology. 18 (12): R504–R505. doi:10.1016/j.cub.2008.03.034. PMC   2974440 . PMID   18579086.
  27. ↑ Dedryver, C-A; Le Gallic, J-F; Mahéo, F; Simon, J-C; Dedryver, F (January 2013). "The genetics of obligate parthenogenesis in an aphid species and its consequences for the maintenance of alternative reproductive modes". Heredity. 110 (1): 39–45. doi:10.1038/hdy.2012.57. PMC   3522239 . PMID   22990313.
  28. ↑ Crews, David; Fitzgerald, Kevin T. (January 1980). "'Sexual' behavior in parthenogenetic lizards (Cnemidophorus)". Proceedings of the National Academy of Sciences. 77 (1): 499–502. doi: 10.1073/pnas.77.1.499 . PMC   348299 . PMID   16592761.
  29. ↑ Tobler, Michael; Schlupp, Ingo (22 June 2005). "Parasites in sexual and asexual mollies (Poecilia, Poeciliidae, Teleostei): a case for the Red Queen?". Biology Letters. 1 (2): 166–168. doi:10.1098/rsbl.2005.0305. PMC   1626213 . PMID   17148156.
  30. ↑ "Apomixis | reproduction | Britannica". www.britannica.com. Retrieved 23 March 2023.
  31. ↑ Zhang, Siqi; Liang, Mei; Wang, Nan; Xu, Qiang; Deng, Xiuxin; Chai, Lijun (March 2018). "Reproduction in woody perennial Citrus: an update on nucellar embryony and self-incompatibility". Plant Reproduction. 31 (1): 43–57. doi:10.1007/s00497-018-0327-4.
  32. ↑ Lotsy, Johannes Paulus; botanistes, Association internationale des (1907). Progressus rei botanicae = Fortschritte der Botanik = Progrès de la botanique = Progress of botany. Vol. 2. Jena: G. Fischer.
  33. ↑ Pigneur, L-M; Hedtke, S M; Etoundi, E; Van Doninck, K (June 2012). "Androgenesis: a review through the study of the selfish shellfish Corbicula spp". Heredity. 108 (6): 581–591. doi:10.1038/hdy.2012.3. PMC   3356815 . PMID   22473310.
  34. 1 2 3 Hedtke, Shannon M.; Stanger-Hall, Kathrin; Baker, Robert J.; Hillis, David M. (May 2008). "All-Male Asexuality: Origin and Maintenance of Androgenesis in the Asian Clam Corbicula". Evolution. 62 (5): 1119–1136. doi:10.1111/j.1558-5646.2008.00344.x. PMID   18266987.
  35. 1 2 3 Tinti, Fausto; Scali, Valerio (November 1992). "Genome exclusion and gametic dapi—dna content in the hybridogenetic Bacillus rossius—grandii benazzii complex (insecta phasmatodea)". Molecular Reproduction and Development. 33 (3): 235–242. doi:10.1002/mrd.1080330302. PMID   1449790.
  36. 1 2 3 Fournier, Denis; Estoup, Arnaud; Orivel, Jérôme; Foucaud, Julien; Jourdan, Hervé; Breton, Julien Le; Keller, Laurent (June 2005). "Clonal reproduction by males and females in the little fire ant". Nature. 435 (7046): 1230–1234. doi:10.1038/nature03705. PMID   15988525.
  37. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Schwander, Tanja; Oldroyd, Benjamin P (28 September 2008). "Androgenesis: where males hijack eggs to clone themselves".
  38. 1 2 3 Komma, D J; Endow, S A (5 December 1995). "Haploidy and androgenesis in Drosophila". Proceedings of the National Academy of Sciences. 92 (25): 11884–11888. doi: 10.1073/pnas.92.25.11884 . PMC   40507 . PMID   8524868.
  39. ↑ "All-male hybrids of a tetrapod Pelophylax esculentus share its origin and genetics of maintenance". 28 September 2024.
  40. 1 2 Matos, I.; Machado, M.P.; Sucena, é.; Collares-Pereira, M.J.; Schartl, M.; Coelho, M.M. (2010). "Evidence for Hermaphroditism in the Squalius alburnoides Allopolyploid Fish Complex". Sexual Development. 4 (3): 170–175. doi:10.1159/000313359.
  41. ↑ Ledford, Heidi (2023). "Making mice with two dads: this biologist rewrote the rules on sexual reproduction". Nature. 624 (7992): 499. Bibcode:2023Natur.624..499L. doi:10.1038/d41586-023-03922-6. PMID   38093054.
  42. 1 2 Christian Pichot; Benjamin Liens; Juana L. Rivera Nava; Julien B. Bachelier; Mohamed El Maâtaoui (January 2008). "Cypress Surrogate Mother Produces Haploid Progeny From Alien Pollen". Genetics. 178 (1): 379–383. doi:10.1534/genetics.107.080572. PMC   2206086 . PMID   18202380.
  43. ↑ Christian Pichot; Bruno Fady; Isabelle Hochu (2000). "Lack of mother tree alleles in zymograms of Cupressus dupreziana A. Camus embryos". Annals of Forest Science. 57 (1): 17–22. Bibcode:2000AnFSc..57...17P. doi: 10.1051/forest:2000108 .
  44. ↑ Pichot, C.; El Maataoui, M.; Raddi, S.; Raddi, P. (2001). "Conservation: Surrogate mother for endangered Cupressus". Nature. 412 (6842): 39. doi: 10.1038/35083687 . PMID   11452293. S2CID   39046191.
  45. ↑ Heesch, Svenja; Serrano-Serrano, Martha; Barrera-Redondo, Josué; Luthringer, Rémy; Peters, Akira F; Destombe, Christophe; Cock, J Mark; Valero, Myriam; Roze, Denis; Salamin, Nicolas; Coelho, Susana M (July 2021). "Evolution of life cycles and reproductive traits: Insights from the brown algae". Journal of Evolutionary Biology. 34 (7): 992–1009. doi:10.1111/jeb.13880.
  46. 1 2 Lynch, A. J. J.; Barnes, R. W.; Vaillancourt, R. E.; Cambecèdes, J. (1998). "Genetic evidence that Lomatia tasmanica (Proteaceae) is an ancient clone" (PDF). Australian Journal of Botany. 46 (1): 25–33. doi:10.1071/BT96120 . Retrieved 11 November 2013.
  47. 1 2 "The Oldest Living Plant Individual". Botanical Electronic News. 8 November 1996. Retrieved 11 November 2013.
  48. 1 2 DeWoody, Jennifer; Rowe, Carol A.; Hipkins, Valerie D.; Mock, Karen E. (2008). ""Pando" Lives: Molecular Genetic Evidence of a Giant Aspen Clone in Central Utah". Western North American Naturalist. 68 (4): 493–497. doi:10.3398/1527-0904-68.4.493. S2CID   59135424.
  49. 1 2 Basavaraju, Yaraguntappa (2023). "Monosex population in aquaculture". Frontiers in Aquaculture Biotechnology. pp. 89–101. doi:10.1016/B978-0-323-91240-2.00012-9. ISBN   978-0-323-91240-2.
  50. ↑ Pichot, C.; El Maâtaoui, M.; Raddi, S.; Raddi, P. (5 July 2001). "Surrogate mother for endangered Cupressus". Nature. 412 (6842): 39. doi:10.1038/35083687. ISSN   0028-0836. PMID   11452293.
  51. ↑ Mehrotra, R. S.; Aneja, K. R. (December 1990). An Introduction to Mycology. New Age International. pp. 83 ff. ISBN   978-81-224-0089-2.
  52. ↑ Cole, Kathleen M.; Sheath, Robert G. (1990). Biology of the red algae. Cambridge University Press. p. 469. ISBN   978-0-521-34301-5.
  53. ↑ Edward G. Reekie; Fakhri A. Bazzaz (2005). Reproductive allocation in plants. Academic Press. p. 99. ISBN   978-0-12-088386-8.
  54. ↑ Stelzer, C.-P.; Schmidt, J.; Wiedlroither, A.; Riss, S. (2010). "Loss of Sexual Reproduction and Dwarfing in a Small Metazoan". PLOS ONE. 5 (9): e12854. Bibcode:2010PLoSO...512854S. doi: 10.1371/journal.pone.0012854 . PMC   2942836 . PMID   20862222.
  55. ↑ Scheuerl, T.; Riss, S.; Stelzer, C.P. (2011). "Phenotypic effects of an allele causing obligate parthenogenesis in a rotifer". Journal of Heredity. 102 (4): 409–415. doi:10.1093/jhered/esr036. PMC   3113615 . PMID   21576287.
  56. ↑ Sandrock, Christoph; Vorburger, Christoph (March 2011). "Single-Locus Recessive Inheritance of Asexual Reproduction in a Parasitoid Wasp". Current Biology. 21 (5): 433–437. doi:10.1016/j.cub.2011.01.070.
  57. ↑ Minelli, Alessandro (2009). Perspectives in Animal Phylogeny and Evolution. Oxford University Press. pp. 123–127. ISBN   978-0-19-856620-5.
  58. ↑ Savage, Juliet Eilperin (23 May 2007). "Female Sharks Can Reproduce Alone, Researchers Find". The Washington Post.
  59. ↑ "'Virgin Birth' By Shark Confirmed: Second Case Ever". ScienceDaily (Press release). Stony Brook University. 11 October 2008.
  60. ↑ Chapman, D. D.; Firchau, B.; Shivji, M. S. (October 2008). "Parthenogenesis in a large-bodied requiem shark, the blacktip Carcharhinus limbatus". Journal of Fish Biology. 73 (6): 1473–1477. doi:10.1111/j.1095-8649.2008.02018.x.
  61. ↑ "Boa constrictor produces fatherless babies". CBC News – Technology & Science. 3 November 2010. Retrieved 20 October 2014.
  62. ↑ Pouchkina-Stantcheva, N. N.; McGee, B. M.; Boschetti, C.; Tolleter, D.; Chakrabortee, S.; Popova, A. V.; Meersman, F.; MacHerel, D.; Hincha, D. K. (2007). "Functional Divergence of Former Alleles in an Ancient Asexual Invertebrate". Science. 318 (5848): 268–71. Bibcode:2007Sci...318..268P. doi: 10.1126/science.1144363 . PMID   17932297.
  63. ↑ Gladyshev, Eugene; Meselson, Matthew (April 2008). "Extreme resistance of bdelloid rotifers to ionizing radiation". Proceedings of the National Academy of Sciences. 105 (13): 5139–5144. Bibcode:2008PNAS..105.5139G. doi: 10.1073/pnas.0800966105 . PMC   2278216 . PMID   18362355.
  64. 1 2 Hespeels, B.; Knapen, M.; Hanot-Mambres, D.; Heuskin, A.-C.; Pineux, F.; Lucas, S.; Koszul, R.; van Doninck, K. (July 2014). "Gateway to genetic exchange? DNA double-strand breaks in the bdelloid rotifer A dineta vaga submitted to desiccation" (PDF). Journal of Evolutionary Biology. 27 (7): 1334–1345. doi:10.1111/jeb.12326. PMID   25105197.
  65. ↑ Welch, David B. Mark; Welch, Jessica L. Mark & Meselson, Matthew (April 2008). "Evidence for degenerate tetraploidy in bdelloid rotifers". Proceedings of the National Academy of Sciences. 105 (13): 5145–9. Bibcode:2008PNAS..105.5145M. doi: 10.1073/pnas.0800972105 . PMC   2278229 . PMID   18362354.
  66. ↑ Schwander, Tanja; Henry, Lee; Crespi, Bernard J. (July 2011). "Molecular Evidence for Ancient Asexuality in Timema Stick Insects". Current Biology. 21 (13): 1129–1134. doi:10.1016/j.cub.2011.05.026. PMID   21683598.
  67. ↑ Brandt, Alexander; Tran Van, Patrick; Bluhm, Christian; Anselmetti, Yoann; Dumas, Zoé; Figuet, Emeric; François, Clémentine M.; Galtier, Nicolas; Heimburger, Bastian; Jaron, Kamil S.; Labédan, Marjorie; Maraun, Mark; Parker, Darren J.; Robinson-Rechavi, Marc; Schaefer, Ina; Simion, Paul; Scheu, Stefan; Schwander, Tanja; Bast, Jens (21 September 2021). "Haplotype divergence supports long-term asexuality in the oribatid mite Oppiella nova". Proceedings of the National Academy of Sciences. 118 (38). doi: 10.1073/pnas.2101485118 . hdl: 20.500.11820/9db5ad45-0faf-4260-a6e2-c6d4406874ba . PMID   34535550.
  68. ↑ van der Kooi, C. J.; Schwander, T. (2014). "Evolution of asexuality via different mechanisms in grass thrips (Thysanoptera: Aptinothrips)". Evolution . 86 (7): 1883–1893. doi:10.1111/evo.12402. PMID   24627993. S2CID   14853526.
  69. ↑ Dawson, K.J. (October 1995). "The Advantage of Asexual Reproduction: When is it Two-fold?". Journal of Theoretical Biology. 176 (3): 341–347. Bibcode:1995JThBi.176..341D. doi:10.1006/jtbi.1995.0203.
  70. ↑ Engelstädter, J. (November 2008). "Constraints on the evolution of asexual reproduction". BioEssays. 30 (11–12): 1138–1150. doi:10.1002/bies.20833. PMID   18937362. S2CID   5357709.
  71. 1 2 Hörandl, Elvira; Hadacek, Franz (2013). "The oxidative damage initiation hypothesis for meiosis". Plant Reproduction. 26 (4): 351–367. doi: 10.1007/s00497-013-0234-7 . PMC   3825497 . PMID   23995700.
  72. ↑ Bernstein, H.; Hopf, F.A.; Michod, R.E. (1987). "The Molecular Basis of the Evolution of Sex". Molecular Genetics of Development. Advances in Genetics. Vol. 24. pp. 323–70. doi:10.1016/s0065-2660(08)60012-7. ISBN   9780120176243. PMID   3324702.
  73. ↑ Avise, J. (2008) Clonality: The Genetics, Ecology and Evolution of Sexual Abstinence in Vertebrate Animals. See pp. 22-25. Oxford University Press. ISBN   019536967X ISBN   978-0195369670

Further reading

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.