Sex in the context of Female anatomy

A species (pl. species) is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. It can be defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. Other ways of defining species include their karyotype, DNA sequence, morphology, behaviour, or ecological niche. In addition, palaeontologists use the concept of the chronospecies since fossil reproduction cannot be examined. The most recent rigorous estimate for the total number of species of eukaryotes is between 8 and 8.7 million. About 14% of these had been described by 2011. All species (except viruses) are given a two-part name, a "binomen". The first part of a binomen is the name of a genus to which the species belongs. The second part is called the specific name or the specific epithet (in botanical nomenclature, also sometimes in zoological nomenclature). For example, Boa constrictor is one of the species of the genus Boa, with constrictor being the specific name.

While the definitions given above may seem adequate at first glance, when looked at more closely they represent problematic species concepts. For example, the boundaries between closely related species become unclear with hybridisation, in a species complex of hundreds of similar microspecies, and in a ring species. Also, among organisms that reproduce only asexually, the concept of a reproductive species breaks down, and each clonal lineage is potentially a microspecies. Although none of these are entirely satisfactory definitions, and while the concept of species may not be a perfect model of life, it is still a useful tool to scientists and conservationists for studying life on Earth, regardless of the theoretical difficulties. If species were fixed and distinct from one another, there would be no problem, but evolutionary processes cause species to change. This obliges taxonomists to decide, for example, when enough change has occurred to declare that a fossil lineage should be divided into multiple chronospecies, or when populations have diverged to have enough distinct character states to be described as cladistic species.

The Charter of the United Nations, also referred to as the UN Charter, is the foundational treaty of the United Nations. It establishes the purposes, governing structure, and overall framework of the United Nations System, including its principal organs: the Secretariat, General Assembly, Security Council, Economic and Social Council, International Court of Justice, and Trusteeship Council. The UN Charter is an important part of public international law, and is the foundation for much of international law governing the use of force, pacific settlement of disputes, arms control, and other important functions of the maintenance of international peace and security.

The UN Charter mandates the United Nations and its member states to maintain international peace and security, uphold international law, achieve "higher standards of living" for their citizens, address "economic, social, health, and related problems", and promote "universal respect for, and observance of, human rights and fundamental freedoms for all without distinction as to race, sex, language, or religion". As a charter and constituent treaty, its rules and obligations are binding on all members and supersede those of other treaties.

Slavery is the ownership of a person as property, especially in regards to their labour. It is an economic phenomenon and its history resides in economic history. Slavery typically involves compulsory work, with the slave's location of work and residence dictated by the party that holds them in bondage. Enslavement is the placement of a person into slavery, and the person is called a slave or an enslaved person.

Many historical cases of enslavement occurred as a result of breaking the law, becoming indebted, suffering a military defeat, or exploitation for cheaper labor; other forms of slavery were instituted along demographic lines such as race or sex. Slaves would be kept in bondage for life, or for a fixed period of time after which they would be granted freedom. Although slavery is usually involuntary and involves coercion, there are also cases where people voluntarily enter into slavery to pay a debt or earn money due to poverty. In the course of human history, slavery was a typical feature of civilization, and existed in most societies throughout history, but it is now outlawed in most countries of the world, except as a punishment for a crime. In general there were two types of slavery throughout human history: domestic and productive.

Gender is the range of social, psychological, cultural, and behavioral aspects of being a man (or boy), woman (or girl), or third gender. Although gender often corresponds to sex, a transgender person may identify with a gender other than their sex assigned at birth. Most cultures use a gender binary, in which gender is divided into two categories, and people are considered part of one or the other; those who are outside these groups may fall under the umbrella term non-binary. Some societies have third genders (and fourth genders, etc.) such as the hijras of South Asia and two-spirit persons native to North America. Most scholars agree that gender is a central characteristic for social organization; this may include social constructs (i.e. gender roles) as well as gender expression.

The word has been used as a synonym for sex, and the balance between these usages has shifted over time. In the mid-20th century, a terminological distinction in modern English (known as the sex and gender distinction) between biological sex and gender began to develop in the academic areas of psychology, sociology, sexology, and feminism. Before the mid-20th century, it was uncommon to use the word gender to refer to anything but grammatical categories. In the West, in the 1970s, feminist theory embraced the concept of a distinction between biological sex and the social construct of gender. The distinction between gender and sex is made by most contemporary social scientists in Western countries, behavioral scientists and biologists, many legal systems and government bodies, and intergovernmental agencies such as the WHO. The experiences of intersex people also testify to the complexity of sex and gender; female, male, and other gender identities are experienced across the many divergences of sexual difference.

Heteronormativity is the definition of heterosexuality as the normative human sexuality. It assumes the gender binary (i.e., that there are only two distinct, opposite genders) and that sexual and marital relations are most fitting between people of the opposite sex.

Heteronormativity creates and upholds a social hierarchy based on sexual orientation with the practice and belief that heterosexuality is deemed as the societal norm. A heteronormative view, therefore, involves alignment of biological sex, sexuality, gender identity and gender roles. Heteronormativity has been linked to heterosexism and homophobia, and the effects of societal heteronormativity on lesbian, gay and bisexual individuals have been described as heterosexual or "straight" privilege.

Intersectionality is an analytical framework for understanding how groups' and individuals' social and political identities result in unique combinations of discrimination and privilege. Examples of these intersecting and overlapping factors include gender, caste, sex, race, ethnicity, class, sexuality, religion, disability, physical appearance, and age. These factors can lead to both empowerment and oppression.

Intersectionality arose in reaction to both white feminism and the then male-dominated Black liberation movement, citing the "interlocking oppressions" of racism, sexism and heteronormativity. It broadens the scope of the first and second waves of feminism, which largely focused on the experiences of women who were white, cisgender, and middle-class, to include the different experiences of women of color, poor women, immigrant women, and other groups, and aims to separate itself from white feminism by acknowledging women's differing experiences and identities.

Heterosexuality is romantic attraction, sexual attraction, or sexual behavior between people of the opposite sex or gender. As a sexual orientation, heterosexuality is "an enduring pattern of emotional, romantic, and/or sexual attractions" to people of the opposite sex. It "also refers to a person's sense of identity based on those attractions, related behaviors, and membership in a community of others who share those attractions." Someone who is heterosexual is commonly referred to as straight.

Along with bisexuality and homosexuality, heterosexuality is one of the three main categories of sexual orientation within the heterosexual–homosexual continuum. Across cultures, most people are heterosexual, and heterosexual activity is by far the most common type of sexual activity. Heterosexuality has mostly been viewed as the normative and most socially dominant form of sexual orientation.

Sexual orientation is an enduring personal pattern of romantic attraction or sexual attraction (or a combination of these) to persons of the opposite sex or gender, the same sex or gender, or to both sexes or more than one gender. Patterns are generally categorized under heterosexuality, homosexuality, and bisexuality, while asexuality (experiencing no sexual attraction to others) is sometimes identified as the fourth category.

These categories are aspects of the more nuanced nature of sexual identity and terminology. For example, people may use other labels, such as pansexual or polysexual, or none at all. According to the American Psychological Association, sexual orientation "also refers to a person's sense of identity based on those attractions, related behaviors, and membership in a community of others who share those attractions". Androphilia and gynephilia are terms used in behavioral science to describe sexual orientation as an alternative to a gender binary conceptualization. Androphilia describes sexual attraction to masculinity; gynephilia describes the sexual attraction to femininity. The term sexual preference largely overlaps with sexual orientation, but is generally distinguished in psychological research. A person who identifies as bisexual, for example, may sexually prefer one sex over the other. Sexual preference may also suggest a degree of voluntary choice, whereas sexual orientation is not a choice.

Mating types are the microorganism equivalent to sexes in multicellular lifeforms and are thought to be the ancestor to distinct sexes. They also occur in multicellular organisms such as fungi.

Moral universalism (also called moral objectivism) is the meta-ethical position that some system of ethics, or a universal ethic, applies universally, that is, for "all similarly situated individuals", regardless of culture, disability, race, sex, religion, nationality, sexual orientation, gender identity, or any other distinguishing feature. Moral universalism is opposed to moral nihilism and moral relativism. However, not all forms of moral universalism are absolutist, nor are they necessarily value monist; many forms of universalism, such as utilitarianism, are non-absolutist, and some forms, such as that of Isaiah Berlin, may be value pluralist.

In addition to the theories of moral realism, moral universalism includes other cognitivist moral theories, such as the subjectivist ideal observer theory and divine command theory, and also the non-cognitivist moral theory of universal prescriptivism.

Prejudice can be an affective feeling towards a person based on their perceived social group membership. The word is often used to refer to a preconceived (usually unfavourable) evaluation or classification of another person based on that person's perceived personal characteristics, such as sex, gender, gender identity, beliefs, values, social class, friendship, age, disability, religion, sexuality, race, ethnicity, language, nationality, culture, complexion, beauty, height, body weight, occupation, wealth, education, criminality, sport-team affiliation, music tastes or other perceived characteristics.

The word "prejudice" can also refer to unfounded or pigeonholed beliefs and it may apply to "any unreasonable attitude that is unusually resistant to rational influence". Gordon Allport defined prejudice as a "feeling, favorable or unfavorable, toward a person or thing, prior to, or not based on, actual experience". Auestad (2015) defines prejudice as characterized by "symbolic transfer", transfer of a value-laden meaning content onto a socially-formed category and then on to individuals who are taken to belong to that category, resistance to change, and overgeneralization.

A gamete (/ˈɡæmiːt/ GAM-eet , reproductive cell, or sex cell, is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. The name gamete was introduced by the German cytologist Eduard Strasburger in 1878.

Gametes of both mating individuals can be the same size and shape, a condition known as isogamy. By contrast, in the majority of species, the gametes are of different sizes, a condition known as anisogamy or heterogamy that applies to humans and other mammals. The human ovum has approximately 100,000 times the volume of a single human sperm cell. The type of gamete an organism produces determines its sex and sets the basis for the sexual roles and sexual selection.

Sexual selection is a mechanism of evolution in which members of one sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex (intrasexual selection). These two forms of selection mean that some individuals have greater reproductive success than others within a population, for example because they are more attractive or prefer more attractive partners to produce offspring. Successful males benefit from frequent mating and monopolizing access to one or more fertile females. Females can maximise the return on the energy they invest in reproduction by selecting and mating with the best males.

The concept was first articulated by Charles Darwin who wrote of a "second agency" other than natural selection, in which competition between mate candidates could lead to speciation. The theory was given a mathematical basis by Ronald Fisher in the early 20th century. Sexual selection can lead males to extreme efforts to demonstrate their fitness to be chosen by females, producing sexual dimorphism in secondary sexual characteristics, such as the ornate plumage of birds-of-paradise and peafowl, or the antlers of deer. Depending on the species, these rules can be reversed. This is caused by a positive feedback mechanism known as a Fisherian runaway, where the passing-on of the desire for a trait in one sex is as important as having the trait in the other sex in producing the runaway effect. Although the sexy son hypothesis indicates that females would prefer male offspring, Fisher's principle explains why the sex ratio is most often 1:1. Sexual selection is widely distributed in the animal kingdom, and is also found in plants and fungi.