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Directional Selection
In population genetics, directional selection, is a mode of negative natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype. Under directional selection, the advantageous allele increases as a consequence of differences in survival and reproduction among different phenotypes. The increases are independent of the dominance of the allele, and even if the allele is recessive, it will eventually become fixed. Directional selection was first described by Charles Darwin in the book ''On the Origin of Species'' as a form of natural selection. Other types of natural selection include stabilizing and disruptive selection. Each type of selection contains the same principles, but is slightly different. Disruptive selection favors both extreme phenotypes, different from one extreme in directional selection. Stabilizing selection favors the middle phenotype, causing the decline ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genetic Distribution
Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species, it ranges widely from the number of species to differences within species and can be attributed to the span of survival for a species. It is distinguished from ''genetic variability'', which describes the tendency of genetic characteristics to vary. Genetic diversity serves as a way for populations to adapt to changing environments. With more variation, it is more likely that some individuals in a population will possess variations of alleles that are suited for the environment. Those individuals are more likely to survive to produce offspring bearing that allele. The population will continue for more generations because of the success of these individuals. The academic field of population genetics includes several hypotheses and theories regarding genetic diversity. The neutral theory of evolution proposes that diversity is the result of the accumulation of neutral substitutions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Salmon
Salmon () is the common name for several commercially important species of euryhaline ray-finned fish from the family Salmonidae, which are native to tributaries of the North Atlantic (genus ''Salmo'') and North Pacific (genus '' Oncorhynchus'') basin. Other closely related fish in the same family include trout, char, grayling, whitefish, lenok and taimen. Salmon are typically anadromous: they hatch in the gravel beds of shallow fresh water streams, migrate to the ocean as adults and live like sea fish, then return to fresh water to reproduce. However, populations of several species are restricted to fresh water throughout their lives. Folklore has it that the fish return to the exact spot where they hatched to spawn, and tracking studies have shown this to be mostly true. A portion of a returning salmon run may stray and spawn in different freshwater systems; the percent of straying depends on the species of salmon. Homing behavior has been shown to depend on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adaptive Evolution In The Human Genome
Adaptive evolution results from the propagation of advantageous mutations through positive selection. This is the modern synthesis of the process which Darwin and Wallace originally identified as the mechanism of evolution. However, in the last half century, there has been considerable debate as to whether evolutionary changes at the molecular level are largely driven by natural selection or random genetic drift. Unsurprisingly, the forces which drive evolutionary changes in our own species’ lineage have been of particular interest. Quantifying adaptive evolution in the human genome gives insights into our own evolutionary history and helps to resolve this neutralist-selectionist debate. Identifying specific regions of the human genome that show evidence of adaptive evolution helps us find functionally significant genes, including genes important for human health, such as those associated with diseases. Methods The methods used to identify adaptive evolution are generally devi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein Primary Structure
Protein primary structure is the linear sequence of amino acids in a peptide or protein. By convention, the primary structure of a protein is reported starting from the amino-terminal (N) end to the carboxyl-terminal (C) end. Protein biosynthesis is most commonly performed by ribosomes in cells. Peptides can also be synthesized in the laboratory. Protein primary structures can be directly sequenced, or inferred from DNA sequences. Formation Biological Amino acids are polymerised via peptide bonds to form a long backbone, with the different amino acid side chains protruding along it. In biological systems, proteins are produced during translation by a cell's ribosomes. Some organisms can also make short peptides by non-ribosomal peptide synthesis, which often use amino acids other than the standard 20, and may be cyclised, modified and cross-linked. Chemical Peptides can be synthesised chemically via a range of laboratory methods. Chemical methods typically synthe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrophobicity Scales
Hydrophobicity scales are values that define the relative hydrophobicity or hydrophilicity of amino acid residues. The more positive the value, the more hydrophobic are the amino acids located in that region of the protein. These scales are commonly used to predict the transmembrane alpha-helices of membrane proteins. When consecutively measuring amino acids of a protein, changes in value indicate attraction of specific protein regions towards the hydrophobic region inside lipid bilayer. The hydrophobic or hydrophilic character of a compound or amino acid is its hydropathic character, hydropathicity, or hydropathy. Hydrophobicity and the hydrophobic effect The hydrophobic effect represents the tendency of water to exclude non-polar molecules. The effect originates from the disruption of highly dynamic hydrogen bonds between molecules of liquid water. Polar chemical groups, such as OH group in methanol do not cause the hydrophobic effect. However, a pure hydrocarbon molecule, for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, providing structure to cells and organisms, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific 3D structure that determines its activity. A linear chain of amino acid residues is called a polypeptide. A protein contains at least one long polypeptide. Short polypeptides, containing less than 20–30 residues, are rarely considered to be proteins and are commonly called peptides. The individual amino acid residues are bonded together by peptide bonds and adjacent amino acid residues. The sequence of amino acid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fitness Landscape ...
Fitness may refer to: * Physical fitness, a state of health and well-being of the body * Fitness (biology), an individual's ability to propagate its genes * Fitness (cereal), a brand of breakfast cereals and granola bars * ''Fitness'' (magazine), a women's magazine, focusing on health and exercise * Fitness and figure competition, a form of physique training, related to bodybuilding * Fitness approximation, a method of function optimization evolutionary computation or artificial evolution methodologies * Fitness function, a particular type of objective function in mathematics and computer science * "Fitness", a 2018 song by Lizzo See also * FitNesse, a web server, a wiki, and a software testing tool *Survival of the fittest "Survival of the fittest" is a phrase that originated from Darwinian evolutionary theory as a way of describing the mechanism of natural selection. The biological concept of fitness is defined as reproductive success. In Darwinian terms, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Local Optimum
In applied mathematics and computer science, a local optimum of an optimization problem is a solution that is optimal (either maximal or minimal) within a neighboring set of candidate solutions. This is in contrast to a global optimum, which is the optimal solution among all possible solutions, not just those in a particular neighborhood of values. Continuous domain When the function to be optimized is continuous, it may be possible to employ calculus to find local optima. If the first derivative exists everywhere, it can be equated to zero; if the function has an unbounded domain, for a point to be a local optimum it is necessary that it satisfy this equation. Then the second derivative test provides a sufficient condition for the point to be a local maximum or local minimum. Search techniques Local search or hill climbing methods for solving optimization problems start from an initial configuration and repeatedly move to an ''improving neighboring configuration''. A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biological Constraints
Biological constraints are factors which make populations resistant to evolutionary change. One proposed definition of constraint is "A property of a trait that, although possibly adaptive in the environment in which it originally evolved, acts to place limits on the production of new phenotypic variants." Constraint has played an important role in the development of such ideas as homology and body plans. Types of constraint Any aspect of an organism that has not changed over a certain period of time could be considered to provide evidence for "constraint" of some sort. To make the concept more useful, it is therefore necessary to divide it into smaller units. First, one can consider the pattern of constraint as evidenced by phylogenetic analysis and the use of phylogenetic comparative methods; this is often termed phylogenetic inertia, or phylogenetic constraint. It refers to the tendency of related taxa sharing traits based on phylogeny. Charles Darwin spoke of this concept in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alaska Department Of Fish And Game
The Alaska Department of Fish and Game (ADF&G) is a department within the government of Alaska. ADF&G's mission is to protect, maintain, and improve the fish, game, and aquatic plant resources of the state, and manage their use and development in the best interest of the economy and the well-being of the people of the state, consistent with the sustained yield principle. ADF&G manages approximately 750 active fisheries, 26 game management units, and 32 special areas. From resource policy to public education, the department considers public involvement essential to its mission and goals. The department is committed to working with tribes in Alaska and with a diverse group of State and Federal agencies. The department works cooperatively with various universities and nongovernmental organizations in formal and informal partnership arrangements, and assists local research or baseline environmental monitoring through citizen science programs. History In 1949, the Territorial Legislat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ugashik River
The Ugashik River is a stream, long, on the Alaska Peninsula of the U.S. state of Alaska. It flows from headwaters near Lower Ugashik Lake and empties into Ugashik Bay, an estuary of the Bering Sea's Bristol Bay. The origin of the name Ugashik is somewhat obscure, although early spelling variants such as Oogashik and Ougashick suggest the name pertains to the source of the river: two waters (lakes) and its muddy character. The river has two major tributaries and one minor: the King Salmon River and the Dog Salmon River both have confluences near the river mouth at Ugashik Bay, while the smaller Dago Creek joins just four miles (6 km) from Smoky Point, where Ugashik Bay and Bristol Bay meet. The river is navigable to a small lagoon located just outside the outlet from Lower Ugashik Lake. A small rapids between the lake and the lagoon serves as the location of a seasonally staffed salmon-counting weir operated by the Alaska Department of Fish and Game. The river ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Egegik River
The Egegik River (pronounced locally, I-ga-gik; Central Alaskan Yup'ik, Igyagiiq; translation, "swift") is a waterway in the U.S. state of Alaska. A biological survey was conducted at the base of the Alaska Peninsula in 1902 by Wilfred Hudson Osgood, which included the Egegik River. Etymology The river has been known by other names and spellings: Ougagouk (1828); Ugaguk (obsolete except on Government maps) or Igagik (Russian variations); also variously Agouyak, lgiagik. Egegak. Ugiagik. Geography The river is located on the Alaska Peninsula. Its watershed originates in the Aleutian Range before it flows westward from Becharof Lake into Bristol Bay via Egegik Bay, an arm of Kvichak Bay. Egegik rapids are reported at the outlet of Becharof Lake. The town of Egegik is situated at the mouth of the river. White bluff is situated on the river's north shore, just inside Cape Chichagof at Bristol Bay. The major tributaries are Kejulik River, Shosky Creek, and King Salmon River. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
