A female has larger gametes than amale. Females and males are results of theanisogamousreproduction system, wherein gametes are of different sizes (unlikeisogamy where they are the same size). The exact mechanism of female gamete evolution remains unknown.
The wordfemale comes from the Latinfemella, the diminutive form offemina, meaning "woman", by way of the Old Frenchfemelle.[7] It is not etymologically related to the wordmale, but in the late 14th century the English spelling was altered to parallel that ofmale.[7][8] It has been used as both noun and adjective since the 14th century.[7] 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.[9] A century later, the meaning was expanded to include non-human female organisms.[9]
For several centuries, using the wordfemale as a noun was considered more respectful than calling her awoman or alady and was preferred for that reason;[9] however, by 1895,[7][10] the linguistic fashion had changed, andfemale was often considered disparaging, usually on the grounds that it grouped humans with other animals.[7][11] In the 21st century, the nounfemale 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).[7] As an adjective,female is still used in some contexts, particularly when the sex of the person is relevant, such asfemale athletes or to distinguish amale nurse from a female one.[12]
The word can also refer to theshape of connectors and fasteners, such as screws, electrical pins, and technical equipment. Under this convention, sockets and receptacles are calledfemale, and the corresponding plugsmale.[17][18]
Oogamous species, which include humans, in which the female gamete is much larger than the male and has no ability tomove. Oogamy is a form ofanisogamy.[21] There is an argument that this pattern was driven by the physical constraints on the mechanisms by which two gametes get together as required forsexual reproduction.[22]
Other than 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 bychytrids,diatoms,water moulds andland plants, among others. In land plants,female andmale designate not only the egg- and sperm-producing organisms and structures, but also the structures of thesporophytes that give rise to male andfemale plants.[citation needed]
Photograph of an adult female human, with an adultmale for comparison. (Both models have partially shaved body hair to show anatomy, i.e., clean-shaven pubic regions.)
A distinguishing characteristic of theclassMammalia is the presence ofmammary glands. Mammary glands are modified sweat glands that produce milk, which is used to feed the young for some time after birth. Only mammalsproduce milk. Mammary glands areobvious inhumans, because the female human body stores large amounts of fatty tissue near the nipples, resulting in prominentbreasts. Mammary glands are present in all mammals, although they are normally redundant in males of the species.[27]
Most mammalian females have two copies of theX chromosome, while males have only one X and one smallerY chromosome; some mammals, such as theplatypus, have different combinations.[28][29] One of the female's X chromosomes israndomly 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 isheterozygous and carries a Z and a W chromosome while the male carries two Z chromosomes. In mammals, females can haveXXX orX.[30][31]
Mammalian femalesbear live young, with the exception ofmonotreme females, which lay eggs.[32] Some non-mammalian species, such asguppies, have analogous reproductive structures; and some other non-mammals, such as somesharks, also bear live young.[33]
Following experiments by French endocrinologist Alfred Jost in the 1940s, it is widely believed that the female is the default sex in mammalian sexual determination. However, this idea was called into question by a 2017 study.[34][35]
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.[25]
Genetic determination
The sex of most mammals, including humans, is genetically determined by theXY sex-determination system where females have XX (as opposed to XY in males) sexchromosomes. It is also possible in a variety of species, including humans, to have otherkaryotypes. Duringreproduction, 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. TheZW 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.[25]
Environmental determination
The young of some species develop into one sex or 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 thegoby) can transform, as adults, from one sex to the other in response to local reproductive conditions (such as a brief shortage of males).[36]
In manyarthropods, sex is determined by infection withparasitic,endosymbioticbacteria of the genusWolbachia. The bacterium can only be transmitted via infected ova, and the presence of the obligate endoparasite may be required for female sexual viability.[37]
The question of how females evolved is mainly a question of why males evolved. The first organisms reproduced asexually, usually viabinary fission, wherein acell 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 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.[38]
The advantages are explained by theevolution of anisogamy, which led to the evolution of male and female function.[39] Before the evolution of anisogamy,mating types in a species wereisogamous: the same size and both could move, catalogued only as "+" or "-" types.[40]: 216 In anisogamy, the mating cells are called gametes. The female gamete is larger than the male gamete, and usually immotile.[41] 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 a few species.[38] Anisogamy appears to have evolved multiple times from isogamy; for example femaleVolvocales (a type of green algae) evolved from the plusmating type.[40]: 222 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.[42]
Femalesex 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 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), andsexual conflict (a sort of sexual arms race). There is also a hypothesis that female genital evolution is the result ofpleiotropy, 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, butnatural selection in general has some role in female genital evolution.[43]
The symbol ♀ (Unicode: U+2640Alt codes: Alt+12), a circle with a small cross underneath, is commonly used to represent females.Joseph Justus Scaliger once speculated that the symbol was associated withVenus, goddess of beauty, because it resembles a bronze mirror with a handle,[44] 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).[45][46]
^Grzimek, Bernhard (2003).Grzimek's Animal Life Encyclopedia. Vol. 1. Gale. pp. 16–17.ISBN978-0-7876-5362-0.Archived from the original on 2024-05-10. Retrieved2020-07-09.During sexual reproduction, each parent animal must form specialized cells known as gametes...In virtually all animals that reproduce sexually, the gametes occur in two morphologically distinct forms corresponding to male and female. These distinctions in form and structure are related to the specific functions of each gamete. The differences become apparent during the latter stages of spermatogenesis (for male gametes) and oogenesis (for female gametes)....After oogenetic meiosis, the morphological transformation of the female gamete generally includes development of a large oocyte that does not move around....The ambiguous term "egg" is often applied to oocytes and other fertilizable stages of female gametes....Spermatogenesis and oogenesis most often occur in different individual animals known as males and females respectively.
^abMartin, Elizabeth; Hine, Robert (2015).A Dictionary of Biology. Oxford University Press. p. 222.ISBN978-0-19-871437-8.Archived from the original on 2023-01-14. Retrieved2020-07-12.Female 1. Denoting the gamete (sex cell) that, during sexual reproduction, fuses with a male gamete in the process of fertilization. Female gametes are generally larger than the male gametes and are usually immotile (see Oosphere; Ovum). 2. (Denoting) an individual organism whose reproductive organs produce only female gametes.
^Palazzani, Laura; Bailes, Victoria; Fella, Marina (2012).Gender in Philosophy and Law. SpringerBriefs in law. Dordrecht : Springer. p. v.ISBN9789400749917.'gender' means human gender, male/female gender (eBook)
^abcdefFowler, Henry W.; Butterfield, Jeremy (2015). "female".Fowler's Dictionary of Modern English Usage (4th ed.). Oxford: Oxford University Press.ISBN978-0-19-966135-0.
^Donald M. Ayers,English Words from Latin and Greek Elements, second edition (1986, University of Arizona Press), p. 113
^Newton-Small, Jay (2016-04-19)."Why We Need to Reclaim the Word 'Female'".TIME. Retrieved2024-05-10.Katherine Martin, head of U.S. dictionaries at Oxford University Press...cites the OED's original entry for female in 1895, in which the editors described its usage as "now commonly avoided by good writers, exc. with contemptuous implication."
^Fowler, H. W.; Butterfield, Jeremy (2015). "female, feminine".Fowler's Dictionary of Modern English Usage (Fourth ed.). Oxford; New York, NY: Oxford University Press.ISBN978-0-19-966135-0.One talks offemale athletes, characters (in fiction and so forth),friends, officers, patients, roles, students, workers, and of the female body, sexuality, etc....Some people object to the use offemale as an adjective, as infemale police officer, female senator, etc. Their objections are based either on the negative connotations offemale as a noun, or on the argument that mentioning the sex of the office holder is automatically sexist, unless the sex of the person denoted is relevant in the context.
^J. Richard Johnson,How to Build Electronic Equipment (1962), p. 167: "To minimize confusion, the connector portions with projecting prongs are referred to as the 'male' portion, and the sockets as the 'female' portion."
^Richard Ferncase,Film and Video Lighting Terms and Concepts (2013), p. 96: "female[:] Refers to a socket type connector, which must receive a male connector"
^David E. Sadava, H. Craig Heller, William K. Purves,Life: The Science of Biology (2008), p. 899
^Franz Engelmann, G. A. Kerkut,The Physiology of Insect Reproduction (2015), p. 29
^Kumar R, Meena M, Swapnil P (2019). "Anisogamy". In Vonk J, Shackelford T (eds.).Anisogamy.Encyclopedia of Animal Cognition and Behavior. Cham: Springer International. pp. 1–5.doi:10.1007/978-3-319-47829-6_340-1.ISBN978-3-319-47829-6.
^Dusenbery, David B. (2009).Living at Micro Scale, Chapter 20. Harvard University Press, Cambridge, MassachusettsISBN978-0-674-03116-6.
^Buck WR & Goffinet B (August 2000). "Morphology and classification of mosses". In Shaw AJ & Goffinet B (ed.).Bryophyte Biology. New York: Cambridge University Press.ISBN978-0-521-66794-4.
^Kumar R, Meena M, Swapnil P (2019). "Anisogamy". In Vonk J, Shackelford T (eds.).Anisogamy.Encyclopedia of Animal Cognition and Behavior. Cham: Springer International. pp. 1–5.doi:10.1007/978-3-319-47829-6_340-1.ISBN978-3-319-47829-6.
^Stearn, William T. (May 1962). "The Origin of the Male and Female Symbols of Biology".Taxon.11 (4):109–113.doi:10.2307/1217734.JSTOR1217734.S2CID87030547.The origin of these symbols has long been of interest to scholars. Probably none now accepts the interpretation of Scaliger that♂ represents the shield and spear of Mars and♀ Venus's looking glass.
^G D Schott,Sex, drugs, and rock and roll: Sex symbols ancient and modern: their origins and iconography on the pedigree,BMJ 2005;331:1509-1510 (24 December),doi:10.1136/bmj.331.7531.1509
