Hereford cattleThe Hereford is a British breed of beef cattle originally from Herefordshire in the West Midlands of England. It has spread to many countries – there are more than five million purebred Hereford cattle in over fifty nations worldwide. The breed was first exported from Britain in 1817, initially to Kentucky. It spread across the United States and Canada, through Mexico, to the great beef-raising countries of South America.
Negative selection (natural selection)In natural selection, negative selection or purifying selection is the selective removal of alleles that are deleterious. This can result in stabilising selection through the purging of deleterious genetic polymorphisms that arise through random mutations. Purging of deleterious alleles can be achieved on the population genetics level, with as little as a single point mutation being the unit of selection. In such a case, carriers of the harmful point mutation have fewer offspring each generation, reducing the frequency of the mutation in the gene pool.
Bighorn sheepThe bighorn sheep (Ovis canadensis) is a species of sheep native to North America. It is named for its large horns. A pair of horns might weigh up to ; the sheep typically weigh up to . Recent genetic testing indicates three distinct subspecies of Ovis canadensis, one of which is endangered: O. c. sierrae. Sheep originally crossed to North America over the Bering Land Bridge from Siberia; the population in North America peaked in the millions, and the bighorn sheep entered into the mythology of Native Americans.
Domestication of animalsThe domestication of animals is the mutual relationship between non-human animals and the humans who have influence on their care and reproduction. Charles Darwin recognized a small number of traits that made domesticated species different from their wild ancestors. He was also the first to recognize the difference between conscious selective breeding (i.e. artificial selection) in which humans directly select for desirable traits, and unconscious selection where traits evolve as a by-product of natural selection or from selection on other traits.
Polled livestockPolled livestock are livestock without horns in species which are normally horned. The term refers to both breeds and strains that are naturally polled through selective breeding and also to naturally horned animals that have been disbudded. Natural polling occurs in cattle, yaks, water buffalo, and goats, and in these animals it affects both sexes equally; in sheep, by contrast, both sexes may be horned, both polled, or only the females polled. The history of breeding polled livestock starts about 6000 years BC.
Human genetic variationHuman genetic variation is the genetic differences in and among populations. There may be multiple variants of any given gene in the human population (alleles), a situation called polymorphism. No two humans are genetically identical. Even monozygotic twins (who develop from one zygote) have infrequent genetic differences due to mutations occurring during development and gene copy-number variation. Differences between individuals, even closely related individuals, are the key to techniques such as genetic fingerprinting.
Cattle in religion and mythologyThere are varying beliefs about cattle in societies and religions. Cattle are considered sacred in Indian religions such as Hinduism, Jainism, Buddhism, Sikhism and in African paganism. Cattle played other major roles in many religions, including those of ancient Egypt, ancient Greece, ancient Israel, ancient Rome. In some regions, especially most states of India, the slaughter of cattle is prohibited and their meat may be taboo. Legislation against the slaughter of cattle is in place throughout most states of India except Kerala and parts of the North-East.
LlamaThe llama (ˈlɑːmə; ˈʎama) (Lama glama) is a domesticated South American camelid, widely used as a meat and pack animal by Andean cultures since the pre-Columbian era. Llamas are social animals and live with others as a herd. Their wool is soft and contains only a small amount of lanolin. Llamas can learn simple tasks after a few repetitions. When using a pack, they can carry about 25 to 30% of their body weight for 8 to 13 km (5–8 miles). The name llama (in the past also spelled "lama" or "glama") was adopted by European settlers from native Peruvians.
Molecular clockThe molecular clock is a figurative term for a technique that uses the mutation rate of biomolecules to deduce the time in prehistory when two or more life forms diverged. The biomolecular data used for such calculations are usually nucleotide sequences for DNA, RNA, or amino acid sequences for proteins. The benchmarks for determining the mutation rate are often fossil or archaeological dates. The molecular clock was first tested in 1962 on the hemoglobin protein variants of various animals, and is commonly used in molecular evolution to estimate times of speciation or radiation.
Genetic erosionGenetic erosion (also known as genetic depletion) is a process where the limited gene pool of an endangered species diminishes even more when reproductive individuals die off before reproducing with others in their endangered low population. The term is sometimes used in a narrow sense, such as when describing the loss of particular alleles or genes, as well as being used more broadly, as when referring to the loss of a phenotype or whole species.
