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Population Dynamics Of Fisheries
A fishery is an area with an associated fish or aquatic population which is harvested for its commercial or recreational value. Fisheries can be wild or farmed. Population dynamics describes the ways in which a given population grows and shrinks over time, as controlled by birth, death, and migration. It is the basis for understanding changing fishery patterns and issues such as habitat destruction, predation and optimal harvesting rates. The population dynamics of fisheries is used by fisheries scientists to determine sustainable yields. The basic accounting relation for population dynamics is the BIDE (Birth, Immigration, Death, Emigration) model, shown as: : ''N''1 = ''N''0 + ''B'' − ''D'' + ''I'' − ''E'' where ''N''1 is the number of individuals at time 1, ''N''0 is the number of individuals at time 0, ''B'' is the number of individuals born, ''D'' the number that died, ''I'' the number that immigrated, and ''E'' the number that emigrated between time 0 a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moofushi Kandu Fish
Alifu Dhaalu Atoll (also known as Southern Ari Atoll or Ari Atholhu Dhekunuburi) is an administrative division of the Maldives. The separation of Ari Atoll (formerly Alifu Atoll) on March 1, 1984, into a Northern and a Southern section formed the two most recent administrative divisions of the Maldives, namely Alifu Alifu Atoll and Alifu Dhaalu Atoll. Alifu Dhaalu Atoll lies south of the line between the channels of Himendhoo Dhekunukandu and Genburugau Kandu. There is an ancient mosque in Fenfushi (Alif Dhaal Atoll), Fenfushi island having wooden decorated ceilings and lacquerwork panels. Buddhist remains, including a stupa, have been found in Ariadhoo Island. Whale sharks are year-round residents of Alif Dhaal Atoll. Geography The South Ari Atoll administrative division consists of the southern part of the geographic or natural Ari Atoll (described as Southern Ari Atoll in this context to differentiate from the official name of the administrative division). The atoll con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Malthus
Thomas Robert Malthus (; 13/14 February 1766 – 29 December 1834) was an English economist, cleric, and scholar influential in the fields of political economy and demography. In his 1798 book ''An Essay on the Principle of Population'', Malthus observed that an increase in a nation's food production improved the well-being of the population, but the improvement was temporary because it led to population growth, which in turn restored the original per capita production level. In other words, humans had a propensity to use abundance for population growth rather than for maintaining a high standard of living, a view and stance that has become known as the "Malthusian trap" or the "Malthusian spectre". Populations had a tendency to grow until the lower class suffered hardship, want, and greater susceptibility to war, famine, and disease, a pessimistic view that is sometimes referred to as a Malthusian catastrophe. Malthus wrote in opposition to the popular view in 18th-century E ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genetic Drift
Genetic drift, also known as random genetic drift, allelic drift or the Wright effect, is the change in the Allele frequency, 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 (due to the law of large numbers). In the middle of the 20th century, vigorous debates occurred over the relative importance of natural selection versus neutral processes, including genetic drift. Ronald Fisher, who explained natural selection using Mendelian inheritance, Mendelian genetics, held the view that genetic drift plays at most a minor role in evolution, and this remained the dominant view for several decades. In 1968, population geneticist Mot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allele Frequency
Allele frequency, or gene frequency, is the relative frequency of an allele (variant of a gene) at a particular locus in a population, expressed as a fraction or percentage. Specifically, it is the fraction of all chromosomes in the population that carry that allele over the total population or sample size. Microevolution is the change in allele frequencies that occurs over time within a population. Given the following: # A particular locus on a chromosome and a given allele at that locus # A population of ''N'' individuals with ploidy ''n'', i.e. an individual carries ''n'' copies of each chromosome in their somatic cells (e.g. two chromosomes in the cells of diploid species) # The allele exists in ''i'' chromosomes in the population then the allele frequency is the fraction of all the occurrences ''i'' of that allele and the total number of chromosome copies across the population, ''i''/(''nN''). The allele frequency is distinct from the genotype frequency, although they a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Idealized Population
In population genetics an idealised population is one that can be described using a number of simplifying assumptions. Models of idealised populations are either used to make a general point, or they are fit to data on real populations for which the assumptions may not hold true. For example, coalescent theory is used to fit data to models of idealised populations. The most common idealized population in population genetics is described in the Wright-Fisher model after Sewall Wright and Ronald Fisher (1922, 1930) and (1931). Wright-Fisher populations have constant size, and their members can mate and reproduce with any other member. Another example is a Moran model, which has overlapping generations, rather than the non-overlapping generations of the Fisher-Wright model. The complexities of real populations can cause their behavior to match an idealised population with an effective population size that is very different from the census population size of the real population. For s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sewall Wright
Sewall Green Wright ForMemRS HonFRSE (December 21, 1889March 3, 1988) was an American geneticist known for his influential work on evolutionary theory and also for his work on path analysis. He was a founder of population genetics alongside Ronald Fisher and J. B. S. Haldane, which was a major step in the development of the modern synthesis combining genetics with evolution. He discovered the inbreeding coefficient and methods of computing it in pedigree animals. He extended this work to populations, computing the amount of inbreeding between members of populations as a result of random genetic drift, and along with Fisher he pioneered methods for computing the distribution of gene frequencies among populations as a result of the interaction of natural selection, mutation, migration and genetic drift. Wright also made major contributions to mammalian and biochemical genetics. Biography Sewall Wright was born in Melrose, Massachusetts, to Philip Green Wright and Elizabe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Effective Population Size
The effective population size (''N''''e'') is the size of an idealised population that would experience the same rate of genetic drift as the real population. Idealised populations are those following simple one- locus models that comply with assumptions of the neutral theory of molecular evolution. The effective population size is normally smaller than the census population size ''N'', partly because chance events prevent some individuals from breeding, and partly due to background selection and genetic hitchhiking. The same real population could have a different effective population size for different properties of interest, such as genetic drift (or more precisely, the speed of coalescence) over one generation vs. over many generations. Within a species, areas of the genome that have more genes and/or less genetic recombination tend to have lower effective population sizes, because of the effects of selection at linked sites. In a population with selection at many loci an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Population
Population is a set of humans or other organisms in a given region or area. Governments conduct a census to quantify the resident population size within a given jurisdiction. The term is also applied to non-human animals, microorganisms, and plants, and has specific uses within such fields as ecology and genetics. Etymology The word ''population'' is derived from the Late Latin ''populatio'' (a people, a multitude), which itself is derived from the Latin word ''populus'' (a people). Use of the term Social sciences In sociology and population geography, population refers to a group of human beings with some predefined feature in common, such as location, Race (human categorization), race, ethnicity, nationality, or religion. Ecology In ecology, a population is a group of organisms of the same species which inhabit the same geographical area and are capable of Sexual reproduction, interbreeding. The area of a sexual population is the area where interbreeding is possi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organism
An organism is any life, living thing that functions as an individual. Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have been proposed to define what an organism is. Among the most common is that an organism has autonomous reproduction, Cell growth, growth, and metabolism. This would exclude viruses, despite the fact that they evolution, evolve like organisms. Other problematic cases include colonial organisms; a colony of eusocial insects is organised adaptively, and has Germ-Soma Differentiation, germ-soma specialisation, with some insects reproducing, others not, like cells in an animal's body. The body of a siphonophore, a jelly-like marine animal, is composed of organism-like zooids, but the whole structure looks and functions much like an animal such as a jellyfish, the parts collaborating to provide the functions of the colonial organism. The evolutiona ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Population Size
In 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. Genetic drift Of the five conditions required to maintain Hardy-Weinberg Equilibrium, infinite population size will always be violated; this means that some degree of genetic drift is always occurring. Smaller population size leads to increased genetic drift, it has been hypothesized that this gives these groups an evolutionary advantage for acquisition of genome complexity. An alternate hypothesis posits that while genetic drift plays a larger role in small populations developing complexity, s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ludwig Von Bertalanffy
Karl Ludwig von Bertalanffy (19 September 1901 – 12 June 1972) was an Austrian biologist known as one of the founders of general systems theory (GST). This is an interdisciplinary practice that describes systems with interacting components, applicable to biology, cybernetics and other fields. Bertalanffy proposed that the classical laws of thermodynamics might be applied to closed systems, but not necessarily to "open systems" such as living things. His mathematical model of an organism's growth over time, published in 1934, is still in use today. Bertalanffy grew up in Austria and subsequently worked in Vienna, London, Canada, and the United States. Biography Ludwig von Bertalanffy was born and grew up in the little village of Atzgersdorf (now Liesing) near Vienna. Ludwig's mother Caroline Agnes Vogel was seventeen when she married the thirty-four-year-old Gustav. Ludwig von Bertalanffy grew up as an only child educated at home by private tutors until he was ten and his par ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pierre François Verhulst
Pierre François Verhulst (28 October 1804, in Brussels – 15 February 1849, in Brussels) was a Belgian mathematician and a doctor in number theory from the University of Ghent in 1825. He is best known for the logistic growth model. Logistic equation Verhulst developed the logistic function in a series of three papers between 1838 and 1847, based on research on modeling population growth that he conducted in the mid 1830s, under the guidance of Adolphe Quetelet; see for details. Verhulst published in the equation: : \frac = rN - \alpha N^2 where ''N''(''t'') represents number of individuals at time ''t'', ''r'' the intrinsic growth rate, and ''\alpha'' is the density-dependent crowding effect (also known as intraspecific competition). In this equation, the population equilibrium (sometimes referred to as the carrying capacity, ''K''), N^*, is : N^* = \frac . In he named the solution the logistic curve. Later, Raymond Pearl and Lowell Reed popularized the equatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
