An organism is defined in a medical dictionary as any living thing that functions as an individual . Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have been proposed to define what an organism is. Among the most common is that an organism has autonomous reproduction , growth , and metabolism . This would exclude viruses , despite the fact that they evolve like organisms. Other problematic cases include colonial organisms ; a colony of eusocial insects is organised adaptively, and has germ-soma specialisation , with some insects reproducing, others not, like cells in an animal's body. The body of a siphonophore , a jelly-like marine animal, is composed of organism-like zooids , but the whole structure looks and functions much like an animal such as a jellyfish , the parts collaborating to provide the functions of the colonial organism.
60-710: An organism 's sex is female ( symbol : ♀ ) if it produces the ovum (egg cell), the type of gamete (sex cell) that fuses with the male gamete (sperm cell) during sexual reproduction . A female has larger gametes than a male . Females and males are results of the anisogamous reproduction system , wherein gametes are of different sizes (unlike isogamy where they are the same size). The exact mechanism of female gamete evolution remains unknown. In species that have males and females, sex-determination may be based on either sex chromosomes , or environmental conditions. Most female mammals , including female humans , have two X chromosomes . Characteristics of organisms with
120-401: A cell splits itself in half. From a strict numbers perspective, a species that is half males/half females can produce half the offspring an asexual population can, because only the females are having offspring. Being male can also carry significant costs, such as in flashy sexual displays in animals (such as big antlers or colorful feathers), or needing to produce an outsized amount of pollen as
180-399: A zoosporangium and zoospores . Others are eucarpic, meaning they produce other structures, such as rhizoids , in addition to the zoosporangium and zoospores. Some chytrids are monocentric, meaning a single zoospore gives rise to a single zoosporangium. Others are polycentric, meaning one zoospore gives rise to many zoosporangium connected by a rhizomycelium. Rhizoids do not have nuclei while
240-511: A female sex vary between different species, having different female reproductive systems , with some species showing characteristics secondary to the reproductive system , as with mammary glands in mammals. In humans, the word female can also be used to refer to gender in the social sense of gender role or gender identity . The word female comes from the Latin femella , the diminutive form of femina , meaning " woman ", by way of
300-569: A few enzymes and molecules like those in living organisms, they have no metabolism of their own; they cannot synthesize the organic compounds from which they are formed. In this sense, they are similar to inanimate matter. Viruses have their own genes , and they evolve . Thus, an argument that viruses should be classed as living organisms is their ability to undergo evolution and replicate through self-assembly. However, some scientists argue that viruses neither evolve nor self-reproduce. Instead, viruses are evolved by their host cells, meaning that there
360-541: A few species. Anisogamy appears to have evolved multiple times from isogamy; for example female Volvocales (a type of green algae) evolved from the plus mating type . Although sexual evolution emerged at least 1.2 billion years ago, the lack of anisogamous fossil records make it hard to pinpoint when females evolved. Female sex organs (genitalia, in animals) have an extreme range of variation among species and even within species. The evolution of female genitalia remains poorly understood compared to male genitalia, reflecting
420-530: A now-outdated belief that female genitalia are less varied than male genitalia, and thus less useful to study. The difficulty of reaching female genitalia has also complicated their study. New 3D technology has made female genital study simpler. Genitalia evolve very quickly. There are three main hypotheses as to what impacts female genital evolution: lock-and-key (genitals must fit together), cryptic female choice (females affect whether males can fertilize them), and sexual conflict (a sort of sexual arms race). There
480-424: A plant in order to get a chance to fertilize a female. Yet despite the costs of being male, there must be some advantage to the process. The advantages are explained by the evolution of anisogamy , which led to the evolution of male and female function. Before the evolution of anisogamy, mating types in a species were isogamous : the same size and both could move, catalogued only as "+" or "-" types. In anisogamy,
540-531: A process of recombination (a primitive form of sexual interaction ). Chytrid Chytridiomycota are a division of zoosporic organisms in the kingdom Fungi , informally known as chytrids . The name is derived from the Ancient Greek χυτρίδιον ( khutrídion ), meaning "little pot", describing the structure containing unreleased zoospores . Chytrids are one of the earliest diverging fungal lineages, and their membership in kingdom Fungi
600-523: A rhizomycelium can. Growth continues until a new batch of zoospores are ready for release. Chytrids have a diverse set of release mechanisms that can be grouped into the broad categories of operculate or inoperculate. Operculate discharge involves the complete or incomplete detachment of a lid-like structure, called an operculum, allowing the zoospores out of the sporangium. Inoperculate chytrids release their zoospores through pores, slits, or papillae. Chytrids are aquatic fungi , though those that thrive in
660-612: A small cross underneath, is commonly used to represent females. Joseph Justus Scaliger once speculated that the symbol was associated with Venus, goddess of beauty , because it resembles a bronze mirror with a handle, but modern scholars consider that fanciful, and the most established view is that the female and male symbols derive from contractions in Greek script of the Greek names of the planets Thouros (Mars) and Phosphoros (Venus). Organism The evolutionary biologists David Queller and Joan Strassmann state that "organismality",
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#1732772972194720-485: A species. Currently, taxonomy in Chytridiomycota is based on molecular data, zoospore ultrastructure and some aspects of thallus morphology and development. In an older and more restricted sense (not used here), the term "chytrids" referred just to those fungi in the class Chytridiomycetes . Here, the term "chytrid" refers to all members of Chytridiomycota. The chytrids have also been included among
780-439: A version of oogamy : The male is motile and the female is stationary. This is the first occurrence of oogamy in kingdom Fungi. Briefly, the monoblephs form oogonia, which give rise to eggs, and antheridia, which give rise to male gametes. Once fertilized, the zygote either becomes an encysted or motile oospore, which ultimately becomes a resting spore that will later germinate and give rise to new zoosporangia. Upon release from
840-445: Is a microorganism such as a protist , bacterium , or archaean , composed of a single cell , which may contain functional structures called organelles . A multicellular organism such as an animal , plant , fungus , or alga is composed of many cells, often specialised. A colonial organism such as a siphonophore is a being which functions as an individual but is composed of communicating individuals. A superorganism
900-401: Is a teleonomic or goal-seeking behaviour that enables them to correct errors of many kinds so as to achieve whatever result they are designed for. Such behaviour is reminiscent of intelligent action by organisms; intelligence is seen as an embodied form of cognition . All organisms that exist today possess a self-replicating informational molecule (genome), and such an informational molecule
960-741: Is a colony, such as of ants , consisting of many individuals working together as a single functional or social unit . A mutualism is a partnership of two or more species which each provide some of the needs of the other. A lichen consists of fungi and algae or cyanobacteria , with a bacterial microbiome ; together, they are able to flourish as a kind of organism, the components having different functions, in habitats such as dry rocks where neither could grow alone. The evolutionary biologists David Queller and Joan Strassmann state that "organismality" has evolved socially, as groups of simpler units (from cells upwards) came to cooperate without conflicts. They propose that cooperation should be used as
1020-405: Is also a hypothesis that female genital evolution is the result of pleiotropy , i.e. unrelated genes that are affected by environmental conditions like low food also affect genitals. This hypothesis is unlikely to apply to a significant number of species, but natural selection in general has some role in female genital evolution. The symbol ♀ ( Unicode : U+2640 Alt codes : Alt+12), a circle with
1080-516: Is also possible in a variety of species, including humans, to have other karyotypes . During reproduction , the male contributes either an X sperm or a Y sperm, while the female always contributes an X egg. A Y sperm and an X egg produce a male, while an X sperm and an X egg produce a female. The ZW sex-determination system , where females have ZW (as opposed to ZZ in males) sex chromosomes, is found in birds, reptiles and some insects and other organisms. The young of some species develop into one sex or
1140-535: Is an argument for viewing viruses as cellular organisms. Some researchers perceive viruses not as virions alone, which they believe are just spores of an organism, but as a virocell - an ontologically mature viral organism that has cellular structure. Such virus is a result of infection of a cell and shows all major physiological properties of other organisms: metabolism , growth, and reproduction , therefore, life in its effective presence. The philosopher Jack A. Wilson examines some boundary cases to demonstrate that
1200-420: Is called trioecy . In Thor manningi (a species of shrimp), females coexist with males and protandrous hermaphrodites . A distinguishing characteristic of the class Mammalia is the presence of mammary glands . Mammary glands are modified sweat glands that produce milk, which is used to feed the young for some time after birth. Only mammals produce milk . Mammary glands are obvious in humans , because
1260-419: Is demonstrated with chitin cell walls , a posterior whiplash flagellum , absorptive nutrition, use of glycogen as an energy storage compound, and synthesis of lysine by the α -amino adipic acid (AAA) pathway. Chytrids are saprobic , degrading refractory materials such as chitin and keratin , and sometimes act as parasites . There has been a significant increase in the research of chytrids since
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#17327729721941320-431: Is generally accepted that the resulting zygote forms a resting spore, which functions as a means of surviving adverse conditions. In some members, sexual reproduction is achieved through the fusion of isogametes (gametes of the same size and shape). This group includes the notable plant pathogens Synchytrium . Some algal parasites practice oogamy : A motile male gamete attaches itself to a nonmotile structure containing
1380-472: Is likely intrinsic to life. Thus, the earliest organisms also presumably possessed a self-replicating informational molecule ( genome ), perhaps RNA or an informational molecule more primitive than RNA. The specific nucleotide sequences in all currently extant organisms contain information that functions to promote survival, reproduction , and the ability to acquire resources necessary for reproduction, and sequences with such functions probably emerged early in
1440-402: Is needed. Chytrids mainly infect algae and other eukaryotic and prokaryotic microbes. The infection can be so severe as to control primary production within the lake. It has been suggested that parasitic chytrids have a large effect on lake and pond food webs. Chytrids may also infect plant species; in particular, Synchytrium endobioticum is an important potato pathogen. Arguably,
1500-460: Is the default sex, while in the poplar genus Populus the default is male. The sex of a particular organism may be determined by genetic or environmental factors, or may naturally change during the course of an organism's life. The sex of most mammals, including humans, is genetically determined by the XY sex-determination system where females have XX (as opposed to XY in males) sex chromosomes . It
1560-486: The Ancient Greek ὀργανισμός , derived from órganon , meaning instrument, implement, tool, organ of sense or apprehension) first appeared in the English language in the 1660s with the now-obsolete meaning of an organic structure or organization. It is related to the verb "organize". In his 1790 Critique of Judgment , Immanuel Kant defined an organism as "both an organized and a self-organizing being". Among
1620-703: The Protoctista , but are now regularly classed as fungi. In older classifications , chytrids, except the recently established order Spizellomycetales , were placed in the class Phycomycetes under the subphylum Myxomycophyta of the kingdom Fungi. Previously, they were placed in the Mastigomycotina as the class Chytridiomycetes. The other classes of the Mastigomycotina, the Hyphochytriomycetes and oomycetes , were removed from
1680-642: The "defining trait" of an organism. Samuel Díaz‐Muñoz and colleagues (2016) accept Queller and Strassmann's view that organismality can be measured wholly by degrees of cooperation and of conflict. They state that this situates organisms in evolutionary time, so that organismality is context dependent. They suggest that highly integrated life forms, which are not context dependent, may evolve through context-dependent stages towards complete unification. Viruses are not typically considered to be organisms, because they are incapable of autonomous reproduction , growth , metabolism , or homeostasis . Although viruses have
1740-433: The 21st century, the noun female is primarily used to describe non-human animals, to refer to biologically female humans in an impersonal technical context (e.g., "Females were more likely than males to develop an autoimmune disease"), or to impartially include a range of people without reference to age (e.g., girls ) or social status (e.g., lady ). As an adjective, female is still used in some contexts, particularly when
1800-475: The Old French femelle . It is not etymologically related to the word male , but in the late 14th century the English spelling was altered to parallel that of male . It has been used as both noun and adjective since the 14th century. Originally, from its first appearance in the 1300s, female exclusively referred to humans and always indicated that the speaker spoke of a woman or a girl. A century later,
1860-411: The belief that many chytrid species are ubiquitous and cosmopolitan. However, recent taxonomic work has demonstrated that this ubiquitous and cosmopolitan morphospecies hide cryptic diversity at the genetic and ultrastructural levels. It was first thought aquatic chytrids (and other zoosporic fungi) were primarily active in fall, winter, and spring. However, recent molecular inventories of lakes during
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1920-514: The capillary network around soil particles are typically considered terrestrial. The zoospore is primarily a means of thoroughly exploring a small volume of water for a suitable substrate rather than a means of long-range dispersal. Chytrids have been isolated from a variety of aquatic habitats, including peats, bogs, rivers, ponds, springs, and ditches, and terrestrial habitats, such as acidic soils, alkaline soils, temperate forest soils, rainforest soils, Arctic and Antarctic soils. This has led to
1980-678: The concept of organism is not sharply defined. In his view, sponges , lichens , siphonophores , slime moulds , and eusocial colonies such as those of ants or naked molerats , all lie in the boundary zone between being definite colonies and definite organisms (or superorganisms). Scientists and bio-engineers are experimenting with different types of synthetic organism , from chimaeras composed of cells from two or more species, cyborgs including electromechanical limbs, hybrots containing both electronic and biological elements, and other combinations of systems that have variously evolved and been designed. An evolved organism takes its form by
2040-473: The corresponding plugs male . Females produce ova , the larger gametes in a heterogamous reproduction system , while the smaller and usually motile gametes, the spermatozoa , are produced by males. Generally, a female cannot reproduce sexually without access to the gametes of a male, and vice versa, but in some species females can reproduce by themselves asexually , for example via parthenogenesis . Patterns of sexual reproduction include: Other than
2100-476: The criteria that have been proposed for being an organism are: Other scientists think that the concept of the organism is inadequate in biology; that the concept of individuality is problematic; and from a philosophical point of view, question whether such a definition is necessary. Problematic cases include colonial organisms : for instance, a colony of eusocial insects fulfills criteria such as adaptive organisation and germ-soma specialisation. If so,
2160-417: The defining difference in the type of gamete produced, differences between males and females in one lineage cannot always be predicted by differences in another. The concept is not limited to animals; egg cells are produced by chytrids , diatoms , water moulds and land plants , among others. In land plants, female and male designate not only the egg- and sperm-producing organisms and structures, but also
2220-437: The discovery of Batrachochytrium dendrobatidis , the causal agent of chytridiomycosis . Species of Chytridiomycota have traditionally been delineated and classified based on development, morphology, substrate, and method of zoospore discharge. However, single spore isolates (or isogenic lines) display a great amount of variation in many of these features; thus, these features cannot be used to reliably classify or identify
2280-422: The evolution of life. It is also likely that survival sequences present early in the evolution of organisms included sequences that facilitate the avoidance of damage to the self-replicating molecule and promote the capability to repair such damages that do occur. Repair of some of the genome damages in these early organisms may have involved the capacity to use undamaged information from another similar genome by
2340-823: The extinction of the golden toad in 1989. Chytridiomycosis has also been implicated in the presumed extinction of the Southern Gastric Brooding Frog, last seen in the wild in 1981, and the Northern Gastric Brooding Frog, last recorded in the wild in March 1985. The process leading to frog mortality is thought to be the loss of essential ions through pores made in the epidermal cells by the chytrid during its replication. Recent research has revealed that elevating salt levels slightly may be able to cure chytridiomycosis in some Australian frog species, although further experimentation
2400-527: The female gamete. In another group, two thalli produce tubes that fuse and allow the gametes to meet and fuse. In the last group, rhizoids of compatible strains meet and fuse. Both nuclei migrate out of the zoosporangium and into the conjoined rhizoids where they fuse. The resulting zygote germinates into a resting spore. Sexual reproduction is common and well known among members of the Monoblepharidomycetes. Typically, these chytrids practice
2460-413: The female human body stores large amounts of fatty tissue near the nipples, resulting in prominent breasts . Mammary glands are present in all mammals, although they are normally redundant in males of the species. Most mammalian females have two copies of the X chromosome , while males have only one X and one smaller Y chromosome ; some mammals, such as the platypus , have different combinations. One of
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2520-650: The female's X chromosomes is randomly inactivated in each cell of placental mammals while the paternally derived X is inactivated in marsupials. In birds and some reptiles, by contrast, it is the female which is heterozygous and carries a Z and a W chromosome while the male carries two Z chromosomes. In mammals, females can have XXX or X . Mammalian females bear live young , with the exception of monotreme females, which lay eggs. Some non-mammalian species, such as guppies , have analogous reproductive structures; and some other non-mammals, such as some sharks , also bear live young. In sex determination for mammals, female
2580-467: The formation of several new zoosporic fungal phyla: Chytridiomycota are unusual among the Fungi in that they reproduce with zoospores. For most members of Chytridiomycota, sexual reproduction is not known. Asexual reproduction occurs through the release of zoospores (presumably) derived through mitosis . Where it has been described, sexual reproduction of chytrids occurs via a variety of methods. It
2640-586: The fungi to be classified as heterokont pseudofungi . The class Chytridiomycetes has over 750 chytrid species distributed among ten orders . Additional classes include the Monoblepharidomycetes , with two orders, and the Hyaloraphidiomycetes with a single order. Molecular phylogenetics , and other techniques such as ultrastructure analysis, has greatly increased the understanding of chytrid phylogeny, and led to
2700-547: The germinated resting spore, zoospores seek out a suitable substrate for growth using chemotaxis or phototaxis . Some species encyst and germinate directly upon the substrate; others encyst and germinate a short distance away. Once germinated, enzymes released from the zoospore begin to break down the substrate and utilize it produce a new thallus . Thalli are coenocytic and usually form no true mycelium (having rhizoids instead). Chytrids have several different growth patterns. Some are holocarpic, which means they only produce
2760-495: The mating cells are called gametes. The female gamete is larger than the male gamete, and usually immotile. Anisogamy remains poorly understood, as there is no fossil record of its emergence. Numerous theories exist as to why anisogamy emerged. Many share a common thread, in that larger female gametes are more likely to survive, and that smaller male gametes are more likely to find other gametes because they can travel faster. Current models often fail to account for why isogamy remains in
2820-399: The meaning was expanded to include non-human female organisms. For several centuries, using the word female as a noun was considered more respectful than calling her a woman or a lady and was preferred for that reason; however, by 1895, the linguistic fashion had changed, and female was often considered disparaging, usually on the grounds that it grouped humans with other animals. In
2880-433: The microfossils are chytrids preserved as parasites on rhyniophytes . These fossils closely resemble the modern genus Allomyces . Holocarpic chytrid remains were found in cherts from Combres in central France that date back to the late Visean . These remains were found along with eucarpic remains and are ambiguous in nature although they are thought to be of chytrids. Other chytrid-like fossils were found in cherts from
2940-422: The most important ecological function chytrids perform is decomposition. These ubiquitous and cosmopolitan organisms are responsible for decomposition of refractory materials, such as pollen , cellulose , chitin , and keratin . There are also chytrids that live and grow on pollen by attaching threadlike structures, called rhizoids, onto the pollen grains. This mostly occurs during asexual reproduction because
3000-461: The other depending on local environmental conditions, e.g. the sex of crocodilians is influenced by the temperature of their eggs. Other species (such as the goby ) can transform, as adults, from one sex to the other in response to local reproductive conditions (such as a brief shortage of males). The question of how females evolved is mainly a question of why males evolved. The first organisms reproduced asexually, usually via binary fission , wherein
3060-501: The partially understood mechanisms of evolutionary developmental biology , in which the genome directs an elaborated series of interactions to produce successively more elaborate structures. The existence of chimaeras and hybrids demonstrates that these mechanisms are "intelligently" robust in the face of radically altered circumstances at all levels from molecular to organismal. Synthetic organisms already take diverse forms, and their diversity will increase. What they all have in common
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#17327729721943120-480: The qualities or attributes that define an entity as an organism, has evolved socially as groups of simpler units (from cells upwards) came to cooperate without conflicts. They propose that cooperation should be used as the "defining trait" of an organism. This would treat many types of collaboration, including the fungus / alga partnership of different species in a lichen , or the permanent sexual partnership of an anglerfish , as an organism. The term "organism" (from
3180-612: The same argument, or a criterion of high co-operation and low conflict, would include some mutualistic (e.g. lichens) and sexual partnerships (e.g. anglerfish ) as organisms. If group selection occurs, then a group could be viewed as a superorganism , optimized by group adaptation . Another view is that attributes like autonomy, genetic homogeneity and genetic uniqueness should be examined separately rather than demanding that an organism should have all of them; if so, there are multiple dimensions to biological individuality, resulting in several types of organism. A unicellular organism
3240-494: The sex of the person is relevant, such as female athletes or to distinguish a male nurse from a female one. Biological sex is conceptually distinct from gender , although they are often used interchangeably. The adjective female can describe a person's sex or gender identity . The word can also refer to the shape of connectors and fasteners , such as screws, electrical pins, and technical equipment. Under this convention, sockets and receptacles are called female, and
3300-444: The structures of the sporophytes that give rise to male and female plants . Species that are divided into females and males are classified as gonochoric in animals, as dioecious in seed plants and as dioicous in cryptogams . In some species, female and hermaphrodite individuals may coexist, a sexual system termed gynodioecy . In a few species, female individuals coexist with males and hermaphrodites ; this sexual system
3360-424: The summer indicate that chytrids are an active, diverse part of the eukaryotic microbial community. One of the least expected terrestrial environments the chytrid thrive in are periglacial soils. The population of the Chytridiomycota species are able to be supported even though there is a lack of plant life in these frozen regions due to the large amounts of water in periglacial soil and pollen blowing up from below
3420-595: The timberline. The chytrid Batrachochytrium dendrobatidis is responsible for chytridiomycosis , a disease of amphibians. Discovered in 1998 in Australia and Panama this disease is known to kill amphibians in large numbers, and has been suggested as a principal cause for the worldwide amphibian decline . Outbreaks of the fungus were found responsible for killing much of the Kihansi Spray Toad population in its native habitat of Tanzania , as well as
3480-537: The upper Pennsylvanian in the Saint-Etienne Basin in France , dating between 300~350 ma . The novel Tom Clancy's Splinter Cell: Fallout (2007) features a species of chytrid that feeds on petroleum and oil-based products. In the story the species is modified using nuclear radiation , to increase the rate at which it feeds on oil. It is then used by Islamic extremists in an attempt to destroy
3540-508: The zoospores that become attached to the pollen continuously reproduce and form new chytrids that will attach to other pollen grains for nutrients. This colonization of pollen happens during the spring time when bodies of water accumulate pollen falling from trees and plants. The earliest fossils of chytrids are from the Scottish Rhynie chert , a Devonian -age lagerstätte with anatomical preservation of plants and fungi. Among
3600-459: Was co-evolution of viruses and host cells. If host cells did not exist, viral evolution would be impossible. As for reproduction, viruses rely on hosts' machinery to replicate. The discovery of viruses with genes coding for energy metabolism and protein synthesis fuelled the debate about whether viruses are living organisms, but the genes have a cellular origin. Most likely, they were acquired through horizontal gene transfer from viral hosts. There
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