Sterility (physiology) in the context of "Interbreeding"

Fertility in colloquial terms refers the ability to have offspring. In demographic contexts, fertility refers to the actual production of offspring, rather than the physical capability to reproduce, which is termed fecundity. The fertility rate is the average number of children born during an individual's lifetime. In medicine, fertility refers to the ability to have children, and infertility refers to difficulty in reproducing naturally. In general, infertility or subfertility in humans is defined as not being able to conceive a child after one year (or longer) of unprotected sex. The antithesis of fertility is infertility, while the antithesis of fecundity is sterility.

In biology, a hybrid is the offspring resulting from combining the qualities of two organisms of different varieties, subspecies, species or genera through sexual reproduction. Generally, it means that each cell has genetic material from two different organisms, whereas an individual where some cells are derived from a different organism is called a chimera. Hybrids are not always intermediates between their parents such as in blending inheritance (a now discredited theory in modern genetics by particulate inheritance), but can show hybrid vigor, sometimes growing larger or taller than either parent. The concept of a hybrid is interpreted differently in animal and plant breeding, where there is interest in the individual parentage. In genetics, attention is focused on the numbers of chromosomes. In taxonomy, a key question is how closely related the parent species are.

Species are reproductively isolated by strong barriers to hybridization, which include genetic and morphological differences, differing times of fertility, mating behaviors and cues, and physiological rejection of sperm cells or the developing embryo. Some act before fertilization and others after it. Similar barriers exist in plants, with differences in flowering times, pollen vectors, inhibition of pollen tube growth, somatoplastic sterility, cytoplasmic-genic male sterility and the structure of the chromosomes. A few animal species and many plant species, however, are the result of hybrid speciation, including important crop plants such as wheat, where the number of chromosomes has been doubled.

Louis XII (27 June 1462 – 1 January 1515), also known as Louis of Orléans was King of France from 1498 to 1515 and King of Naples (as Louis III) from 1501 to 1504. The son of Charles, Duke of Orléans, and Marie of Cleves, he succeeded his second cousin once removed and brother-in-law, Charles VIII, who died childless in 1498.

Louis was the second cousin of King Louis XI, who compelled him to marry the latter's disabled and supposedly sterile daughter Joan. By doing so, Louis XI hoped to extinguish the Orléans cadet branch of the House of Valois. When Louis XII became king in 1498, he had his marriage with Joan annulled by Pope Alexander VI and instead married Anne, Duchess of Brittany, the widow of Charles VIII. This marriage allowed Louis to reinforce the personal Union of Brittany and France.

John Burdon Sanderson Haldane FRS (/ˈhɔːldeɪn/; 5 November 1892 – 1 December 1964), nicknamed "Jack" or "JBS", was a British-born scientist who later moved to India and acquired Indian citizenship. He worked in the fields of physiology, genetics, evolutionary biology, and mathematics. With innovative use of statistics in biology, he was one of the founders of neo-Darwinism. Despite his lack of an academic degree in the field, he taught biology at the University of Cambridge, the Royal Institution, and University College London. Renouncing his British citizenship, he became an Indian citizen in 1961 and worked at the Indian Statistical Institute until his death in 1964.

Haldane's article on abiogenesis in 1929 introduced the "primordial soup theory", which became the foundation for the concept of the chemical origin of life. He established human gene maps for haemophilia and colour blindness on the X chromosome, and codified Haldane's rule on sterility in the heterogametic sex of hybrids in species. He correctly proposed that sickle-cell disease confers some immunity to malaria. He was the first to suggest the central idea of in vitro fertilisation, as well as concepts such as hydrogen economy, cis and trans-acting regulation, coupling reaction, molecular repulsion, the darwin (as a unit of evolution), and organismal cloning.

Louis XII (27 June 1462 – 1 January 1515), also known as Louis of Orléans, was King of France from 1498 to 1515 and King of Naples (as Louis III) from 1501 to 1504. The son of Charles, Duke of Orléans, and Marie of Cleves, he succeeded his second cousin once removed and brother-in-law, Charles VIII, who died childless in 1498.

Louis was the second cousin of King Louis XI, who compelled him to marry the latter's disabled and supposedly sterile daughter Joan. By doing so, Louis XI hoped to extinguish the Orléans cadet branch of the House of Valois. When Louis XII became king in 1498, he had his marriage with Joan annulled by Pope Alexander VI and instead married Anne, Duchess of Brittany, the widow of Charles VIII. This marriage allowed Louis to reinforce the personal Union of Brittany and France.