The reasoning behind this is that if the parents of the hybrid offspring each have naturally selected traits for their own different environments, the hybrid offspring will bear traits from both, and would not fit either niche as well as either parent. The low fitness of the hybrids would cause selection to favour assortative mating, which would reduce hybridization.
This is sometimes called the Wallace effect after the evolutionary biologist Alfred Russel Wallace who suggested in the late 19th century that it might be an important factor in speciation.
If the hybrid offspring are more fit than their ancestors, then the populations will merge back into the same species within the area they are in contact.
Reinforcement is required for separation when there is a "hybrid zone" between two forms of a species. Hybrid zones are regions where diverged populations meet and interbreed. Hybrid offspring are very common in these regions, which are usually created by diverged species coming into secondary contact.
Without reinforcement the two populations or species would have uncontrollable interbreeding. Reinforcement may be induced in artificial selection experiments as described above.
Calhoun County, Alabama
Calhoun County is a county in the U.S. state of Alabama. As of 2010 the population was 118,572. It is included in the Anniston-Oxford Metropolitan Statistical Area. Its county seat is Anniston.
Benton County was formed on December 18, 1832. It was named for Thomas Hart Benton, a member of the United States Senate from Missouri. The first county seat was at Jacksonville.
An F4 tornado struck here on Palm Sunday March 27, 1994. It destroyed Piedmont's Goshen United Methodist Church twelve minutes after the National Weather Service of Birmingham issued a tornado warning for northern Calhoun, southeastern Etowah, and southern Cherokee.
According to the 2000 census, the county has a total area of . (or 99.37%) is land and (or 0.63%) is water.
Calhoun County is home to the Anniston Museum of Natural History and the Berman Museum of World History. It also contains a part of the Talladega National Forest.
Dallas (1978 TV series)
Dallas is an American soap opera. It is about the Ewings, a family from Texas involved in oil and cattle ranching. The show began as a television miniseries during April 1978. It was broadcasted until May 3, 1991 on CBS. The cast included Charlene Tilton, Victoria Principal, Priscilla Presley, Patrick Duffy, and Larry Hagman as J.R. Ewing. The series lasted for fourteen seasons.
The show was revived on TNT in June 2012.
Calhoun County, Arkansas
Calhoun County is a county in Arkansas.
Calhoun County, Georgia
Calhoun County is a county in Georgia. Its county seat is Morgan.
Calhoun County, Illinois
Calhoun County is a county in Illinois.
Elasmobranchii
Elasmobranchii is a subclass of the Chondrichthyes or cartilaginous fish. It includes the modern sharks and the rays and skates.
Fossilised shark teeth are known from the early Devonian, around 400 million years ago. During the following Carboniferous period, the sharks underwent a period of diversification, with many new forms evolving. Many of these became extinct during the Permian, but the remaining sharks underwent a second burst of adaptive radiation during the Jurassic, around which time the skates and rays first appeared.
Earl Wilbur Sutherland Jr.
Earl Wilbur Sutherland, Jr. (November 19, 1915 – March 9, 1974) was an American pharmacologist and biochemist. He won the Nobel Prize in Physiology or Medicine in 1971 for his discoveries concerning the mechanisms of the action of hormones. He was born in Burlingame, Kansas in 1915 and died in Miami, Florida, United States in 1974.
Persian Wikipedia
Persian Wikipedia is a member of Wikimedia Foundation. It started work in December 2003. founder of Persian version is Roozbeh Pour-Nader.
It is the 18th largest edition by article count. Persian Wikipedia has currently more than 500,000 articles.
Many of the first articles on the Persian Wikipedia were about chemical materials and historical subjects. The Wikipedia added geography and religious subjects soon after. On December 16, 2004, the Wikipedia reached 10,000 articles.
Edward B. Lewis
Edward B. Lewis (May 20, 1918 – July 21, 2004) was an American geneticist. He shared the 1995 Nobel Prize in Physiology or Medicine.
Lewis was born in Wilkes-Barre, Pennsylvania He received a BA in Biostatistics from the University of Minnesota in 1939.
In 1942 Lewis received a PhD from California Institute of Technology (Caltech), working on "Drosophila melanogaster" under the guidance of Alfred Sturtevant.
After serving as a meteorologist in the U.S. Air Force in World War II, Lewis joined the Caltech faculty in 1946 as an instructor. In 1956 he was appointed Professor of Biology, and in 1966 the Thomas Hunt Morgan Professor of Biology.
His Nobel Prize winning studies with "Drosophila" founded the field of developmental genetics and laid the groundwork for our current understanding of the universal, evolutionarily conserved strategies controlling animal development.
His key publications in the fields of genetics, developmental biology, radiation and cancer are available in a book.
During the 1950s, Lewis studied the effects of radiation from X-rays, nuclear fallout and other sources as possible causes of cancer. He reviewed medical records from survivors of the atomic bombings of Hiroshima and Nagasaki, as well as radiologists and patients exposed to X-rays. Lewis concluded that "health risks from radiation had been underestimated". Lewis published articles in "Science" and other journals and made a presentation to a Congressional committee on atomic energy in 1957.
At the scientific level of the debate, the crucial question was whether the "threshold theory" was valid or whether, as Lewis insisted, the effects of radioactivity were "linear with no threshold", where every exposure to radiation had a long-term cumulative effect.
In a series of experiments with the fruit-fly "Drosophila", Lewis was able to identify a complex of genes whose proteins bind to the regulatory regions of target genes. The latter then activate or repress cell processes which direct the final development of the organism.
Furthermore, the sequence of these control genes show "co-linearity": the order of the loci in the chromosome parallels the order in which the loci are expressed in segments along the body. Not only that, but this cluster of master control genes programs the development of all higher organisms.
Each of the genes contains a homeobox, a remarkably conserved DNA sequence. This suggests the complex itself arose by gene duplication.
In his Nobel lecture, Lewis said "Ultimately, comparisons of the [control complexes] throughout the animal kingdom should provide a picture of how the organisms, as well as the [control genes] have evolved".
Christine Baranski
Christine Jane Baranski (b. 2 May 1952) is an American Actress, Singer and Producer. On stage, she played Mrs. Lovett in "Sweeney Todd" and the title character in "Mame". She has also acted in multiple movies. Baranski was born in Buffalo, New York.
Angela Burdett-Coutts
Angela Georgina Burdett-Coutts, 1st Baroness Burdett-Coutts (21 April 1814 – 30 December 1906), born Angela Georgina Burdett, was a noted nineteenth century philanthropist. She was the daughter of Sir Francis Burdett, 5th Baronet and Sophia Coutts, daughter of Thomas Coutts the banker. In 1837 she became the wealthiest woman in England when she inherited her grandfather's fortune of nearly three million pounds sterling. At the same time she got a Royal Licence (permission from the monarch) to join her father's and grandfather's surnames and become Angela Burdett-Coutts.