F1 hybrid

In his cross-pollination experiments involving two true-breeding, or homozygous, parents, Mendel found that the resulting F1 generation was heterozygous and consistent.

For mass production of F1 hybrids with uniform phenotype, the parent plants must have predictable genetic effects on the offspring.

Inbreeding and selection for uniformity for multiple generations ensures that the parent lines are almost homozygous.

The divergence between the (two) parent lines promotes improved growth and yield characteristics in offspring through the phenomenon of heterosis ("hybrid vigour" or "combining ability").

[4] In 1960, 99% of all corn, 95% of sugar beet, 80% of spinach, 80% of sunflowers, 62% of broccoli, and 60% of onions planted in the United States were F1 hybrids.

F2 hybrids, the result of self or cross-pollination of F1s, lack the consistency of F1s, though they may retain some desirable traits and can be produced more cheaply because hand pollination or other interventions are not required.

[6] Mules are F1 hybrids between horses (mares) and donkeys (jacks); the opposite sex cross results in hinnies.

[7] As explained in the International Journal of Fauna and Biological Studies,[citation needed] there are four reasons for species hybridizations: Small population size can be caused by inadequate or obliterated natural habitats that lead to species escaping to other habitats and as a result, this may lead to lesser mate availability and can cause breeding between distinct species.

[8] Habitat fragmentation and species introduction can be man-made or caused by mother nature such as deforestation, desertification, eutrophication, urbanization, water oil extraction causing changes in the ecosystem that leads to animal migration or evading new surroundings.

Hybrid vigour is defined as a species becoming sturdier, more dynamic, and stronger than the parents.