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The male parent of a horse, a stallion, is commonly known as the sire and the female parent, the mare, is called the dam. [1] Both are genetically important, as each parent genes can be existent with a 50% probability in the foal. Contrary to popular misuse, "colt" refers to a young male horse only; "filly" is a young female.
Chickens of both sexes develop male-type plumage after gonadectomization. Strictly speaking, they develop a neutral plumage with long acute feathers, like those of male plumage, because ovarian hormone is also necessary to develop female plumage. [6] It is well known that some of the main estrogens derive from androgens.
Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant males and females will sexually reproduce and have offspring together.
Figure 1. Feathering types in ten-day-old chicks.Left: Fast normal-feathering chick. Right: Delayed-feathering chick carrying sex-linked K gene. Delayed-feathering in chickens is a genetically determined delay in the first weeks of feather growing, which occurs normally among the chicks of many chicken breeds and no longer manifests itself once the chicken completes adult plumage.
Ovo-viviparity: or oviparity with retention of zygotes in either the female's or in the male's body, but there are no trophic interactions between zygote and parents. [1] This mode is found in the slowworm, Anguis fragilis. In the sea horse, zygotes are retained in the male's ventral "marsupium".
The evolutionary benefit to this phenomenon is that a male can fertilize multiple females. [6] The male may be reinvigorated repeatedly for successful insemination of multiple females. [7] This type of mating system can be referred to as polygyny, where one male has multiple female mates, but each female mates with only one or a few males. [5]
The polygyny threshold model also shows the effects of female reproductive success when multiple females in the same territory mate with one male. In this situation, the female has the option of breeding with an unmated male in a poor-quality territory or with an already-mated male in a high-quality territory. The second breeding female will ...
1951 news item about breeding and sexing chicks in the Netherlands, with English subtitles. Chick sexing is the method of distinguishing the sex of chickens and other hatchlings, usually by a trained person called a chick sexer or chicken sexer. [1]