Genetic driftGenetic drift, also known as random genetic drift, allelic drift or the Wright effect, is the change in the frequency of an existing gene variant (allele) in a population due to random chance. Genetic drift may cause gene variants to disappear completely and thereby reduce genetic variation. It can also cause initially rare alleles to become much more frequent and even fixed. When few copies of an allele exist, the effect of genetic drift is more notable, and when many copies exist, the effect is less notable.
Population sizeIn population genetics and population ecology, population size (usually denoted N) is a countable quantity representing the number of individual organisms in a population. Population size is directly associated with amount of genetic drift, and is the underlying cause of effects like population bottlenecks and the founder effect. Genetic drift is the major source of decrease of genetic diversity within populations which drives fixation and can potentially lead to speciation events.
Allochronic speciationAllochronic speciation (also known as allochronic isolation, or temporal isolation) is a form of speciation (specifically ecological speciation) arising from reproductive isolation that occurs due to a change in breeding time that reduces or eliminates gene flow between two populations of a species. The term allochrony is used to describe the general ecological phenomenon of the differences in phenology that arise between two or more species—speciation caused by allochrony is effectively allochronic speciation.
Arabidopsis thalianaArabidopsis thaliana, the thale cress, mouse-ear cress or arabidopsis, is a small plant from the mustard family (Brassicaceae), native to Eurasia and Africa. Commonly found along the shoulders of roads and in disturbed land, it is generally considered a weed. A winter annual with a relatively short lifecycle, A. thaliana is a popular model organism in plant biology and genetics. For a complex multicellular eukaryote, A. thaliana has a relatively small genome of around 135 megabase pairs.
TomatoThe tomato (təmeɪtoʊ or təmaːtoʊ) is the edible berry of the plant Solanum lycopersicum, commonly known as the tomato plant. The species originated in western South America, Mexico, and Central America. The Nahuatl word tomatl gave rise to the Spanish word tomate, from which the English word tomato derived. Its domestication and use as a cultivated food may have originated with the indigenous peoples of Mexico.
ArabidopsisArabidopsis (rockcress) is a genus in the family Brassicaceae. They are small flowering plants related to cabbage and mustard. This genus is of great interest since it contains thale cress (Arabidopsis thaliana), one of the model organisms used for studying plant biology and the first plant to have its entire genome sequenced. Changes in thale cress are easily observed, making it a very useful model. Currently, the genus Arabidopsis has nine species and a further eight subspecies recognised.
Chimpanzee–human last common ancestorThe chimpanzee–human last common ancestor (CHLCA) is the last common ancestor shared by the extant Homo (human) and Pan (chimpanzee and bonobo) genera of Hominini. Estimates of the divergence date vary widely from thirteen to five million years ago. In human genetic studies, the CHLCA is useful as an anchor point for calculating single-nucleotide polymorphism (SNP) rates in human populations where chimpanzees are used as an outgroup, that is, as the extant species most genetically similar to Homo sapiens.
TomatilloThe tomatillo (Physalis philadelphica and Physalis ixocarpa), also known as the Mexican husk tomato, is a plant of the nightshade family bearing small, spherical, and green or green-purple fruit of the same name. Tomatillos originated in Mexico and were cultivated in the pre-Columbian era. A staple of Mexican cuisine, they are eaten raw and cooked in a variety of dishes, particularly salsa verde. The tomatillo is a perennial plant but is generally grown for agriculture each year as if it were an annual.
European AmericansEuropean Americans (also referred to as White Americans) are Americans of native European ancestry. This term includes people who are descended from the first European settlers in the United States as well as people who are descended from more recent European arrivals. European Americans have been the largest panethnic group in the United States since about the 17th century. The Spaniards are thought to be the first Europeans to establish a continuous presence in what is now the contiguous United States, with Martín de Argüelles ( () 1566) in St.
European emigrationEuropean emigration is the successive emigration waves from the European continent to other continents. The origins of the various European diasporas can be traced to the people who left the European nation states or stateless ethnic communities on the European continent. From 1500 to the mid-20th century, 60-65 million people left Europe, of which less than 9% went to tropical areas (the Caribbean, Asia, and Africa).
