Female (♀) is the
sex of an
organism, or a part of an organism, which produces mobile
ova (egg cells).
Defining Characteristics
The ova are defined as the larger
gametes in a
heterogamous reproduction system, while the smaller, usually
motile gamete, the
spermatozoon, is produced by the
male. A female individual cannot reproduce
sexually without access to the gametes of a
male (an exception is
parthenogenesis). Some organisms can reproduce both
sexually and
asexually.
There is no single genetic mechanism behind sex differences in different species and the existence of two sexes seems to have
evolved multiple times independently in different
evolutionary lineages. 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 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 the structures of the
sporophytes that give rise to male and female plants.
Etymology and usage
The word
female comes from the Latin
femella, the diminutive form of
femina, meaning "
woman," which is not actually related to the word "male." In the late 14th century, the English spelling was altered so that the word paralleled the spelling of "male."
Mammalian female
The distinguishing characteristic of the
class Mammalia is the presence of
mammary glands. The mammary glands are modified sweat glands that produce
milk, which is used to feed the young during the period of time shortly after birth. Only mammals have the capacity to
produce milk. The presence of mammary glands is
most obvious on
humans, due to the tendency of the female human body to store large amounts of fatty tissue near the nipples, resulting in prominent
breasts, although today some human females also
surgically augment their breast size. However, mammary glands are present in all mammals, although they are
vestigial in the male of the species.
The mammalian female is characterized by having two copies of the
X chromosome as opposed to the male which carries only one X and one smaller
Y chromosome. To compensate for the difference in size, one of the female's X chromosomes is
randomly inactivated in each cell. In birds, by contrast, it is the female who is
heterozygous and carries a Z and a W chromosome whilst the male carries two Z chromosomes.
Mammalian females are characterized in that they all bear live young (with the rare exception of
monotremes, which lay eggs). This is not totally unique, as some animals, such as
guppies have analogous reproductive structures. In addition, some other non-mammalian animals, such as
sharks, whose eggs hatch inside their bodies also have the appearance of bearing live young.
Symbol
A common symbol used to represent the female sex is ♀ (
Unicode: U+2640
Alt codes: Alt+12), a circle with a small cross underneath. According to Schott, "The most established view is that the male and female symbols "are derived from contractions in Greek script of the Greek names of these planets, namely Thouros (Mars) and Phosphoros (Venus). These derivations have been traced by Renkama who illustrated how Greek letters can be transformed into the graphic male and female symbols still recognised today." Thouros was abbreviated by θρ, and Phosphoros by Φκ, which were contracted into the modern symbols.
Sex determination
The
sex of a particular organism may be determined by a number of factors. These may be genetic or environmental, or may naturally change during the course of an organism's life. Although most species with male and female sexes have individuals that are either male or female,
hermaphroditic animals have both male and female reproductive organs.
Genetic determination
Most
mammals, including
humans, are genetically determined as such by the
XY sex-determination system where males have an XY (as opposed to XX) sex
chromosome. During
reproduction, a male can give either an X sperm or a Y sperm, while a female can only give an X egg. A Y sperm and an X egg produce a
boy, while an X sperm and an X egg produce a
girl. The
ZW sex-determination system, where males have a ZZ (as opposed to ZW) sex chromosome may be found in
birds and some
insects and other organisms. Members of
Hymenoptera, such as
ants and
bees, are determined by
haplodiploidy, where most males are
haploid and females and some sterile males are
diploid.
Environmental determination
Some species develop into one sex or the other depending on local environmental conditions, e.g. many crocodilians' sex is influenced by the temperature of their eggs. Other species (such as the
goby) are capable of transforming, as adults, from one sex to the other in response to local reproductive conditions (such as a shortage of males). In humans and most mammals, sex is determined chromosomally -- a Y sperm will produce a male offspring and an X sperm a female.
See also
Sources
Ayers, Donald M.
English Words from Latin and Greek Elements. Second Edition. 1986. University of Arizona Press. United States.
