Selection

Selection: Encyclopedia - Balancing selection

Balancing selection refers to forms of natural selection which work to maintain genetic polymorphisms (or multiple alleles) within a population. Balancing selection is in contrast to directional selection which favor a single allele. A balanced polymorphism is a situation in which balancing selection within a population is able to maintain stable frequencies of two or more phenotypic forms. Note balancing selection will not always result in an observable phenotypic difference beca ...

Selection: Encyclopedia II - Selection - Overview Whether or not selection takes place depends on the conditions in which the individuals of a species find themselves. Adults, juveniles, embryos, and even eggs and sperm may undergo selection. Factors fostering selection include limits on resources (nourishment, habitat space, mates) and the existence of threats (predators, disease, adverse weather). Biologists often refer to such factors as selective pressures. Natural selection is the most familiar type of selection by name. The breeding of dogs, cows and horses, however, rep ...

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Selection: Encyclopedia - Artificial selection

In the theory of evolution, artificial selection is the process of intentional or unintentional modification of a species through human actions which encourage the breeding of certain traits over others. When the process leads to undesirable outcome, it is called negative selection. Charles Darwin originally coined the term in order to contrast this process from what he called natural selection. He noted that many domesticated animals and plants had special properties that were developed by intentionally encouraging the ...

Selection: Encyclopedia - Clonal selection

The "clonal selection theory" has become a widely accepted model for how the immune system responds to infection and how certain types of B and T lymphocytes are selected for destruction of specific antigens invading the body. Clonal selection - Early Work. In 1954, immunologist Niels Jerne put forward a theory which stated that there is already a vast array of lymphocytes in the body prior to any infection. The entrance of an antigen into the body results in only one type of lymphocyte to match it and prod ...

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Selection: Encyclopedia - Adverse selection

Adverse selection or anti-selection is a term used in economics and insurance. On the most abstract level, it refers to a market process in which bad results occur due to information asymmetries between buyers and sellers: the "bad" products or customers are more likely to be selected. Adverse selection - Example: insurance. The term adverse selection was originally used in insurance. It describes a situation where the people who take out insurance are more likely to make a claim than the population ...

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Selection: Encyclopedia - Adaptation and Natural Selection

Adaptation and Natural Selection: A Critique of Some Current Evolutionary Thought is a 1966 book by the American George C. Williams on evolutionary biology. In it, Williams outlines a gene-centric view of evolution, disparaging group selection and progress. This viewpoint was subsequently adopted by the scientific community in the Williams revolution. The book takes its title from a lecture by George Gaylord Simpson in January 1947 at the University of Princeton. The concepts were popularised amongst th ...

Selection: Encyclopedia - Cosmological natural selection

Cosmological natural selection is a hypothesis proposed by Lee Smolin intended as a scientific alternative to the anthropic principle. It addresses the problem of complexity in our universe, which is largely unexplained. Just a few minor changes in the mass of certain elementary particles or in the strength of the forces of the universe would prevent atoms from forming, let alone galaxies. Being that natural selection has explained the complexity of life so well in biology, this concept is borrowed and applied to cosmology in an attem ...

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Selection: Encyclopedia II - Natural selection - Mechanisms of natural selection

In Chapter 4 of The Origin of Species, Darwin wrote: It may be said that natural selection is daily and hourly scrutinising, throughout the world, every variation, even the slightest; rejecting that which is bad, preserving and adding up all that is good; silently and insensibly working, whenever and wherever opportunity offers, at the improvement of each organic being in relation to its organic and inorganic conditions of life. We see nothing of these slow changes in progress, until the hand of time has marked the lon ...

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Selection

A Wisdom Archive on Selection

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