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Secondary Contact
Secondary contact is the process in which two allopatricaly distributed populations of a species are geographically reunited. This contact allows for the potential for the exchange of genes, dependent on how reproductively isolated the two populations have become. There are several primary outcomes of secondary contact: extinction of one species, fusion of the two populations back into one, reinforcement, the formation of a hybrid zone, and the formation of a new species through hybrid speciation. Extinction One of the two populations may go extinct due to competitive exclusion after secondary contact. This tends to happen when the two populations have strong reproductive isolation and significant overlap in their niche. A possible way to prevent extinction is if there is an advantage to being rare. For example, sexual imprinting and male-male competition may prevent extinction. The population that goes extinct may leave behind some of its genes in the surviving population if ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Consequences Of Secondary Contact Schematic
Consequence may refer to: * Logical consequence, also known as a ''consequence relation'', or ''entailment'' * In operant conditioning, a result of some behavior * Consequentialism, a theory in philosophy in which the morality of an act is determined by its effects * Unintended consequences * In logic, a consequent is the second half of a hypothetical proposition or consequences * Consequent (music), the second half of a period (music) Games * Consequences (game), a parlour game Fiction * ''Consequences'' (novel), a 1919 novel by E. M. Delafield * "Consequences" (Kipling story), an 1888 short story by Rudyard Kipling * "Consequences" (Cather story), a 1915 short story by Willa Cather Film and TV * ''Die Konsequenz'' (English: ''The Consequence''), a 1977 West German film * '' Anjaam'' (English: ''Consequence''), a 1994 Hindi film * ''Anjaam (1940 film)'', an earlier Hindi film of the same name * Consequence (film), a 2003 action thriller film starring Armand Assante * ''C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biodiversity Loss
Biodiversity loss includes the worldwide extinction of different species, as well as the local reduction or loss of species in a certain habitat, resulting in a loss of biological diversity. The latter phenomenon can be temporary or permanent, depending on whether the environmental degradation that leads to the loss is reversible through ecological restoration/ecological resilience or effectively permanent (e.g. through land loss). The current global extinction (frequently called the sixth mass extinction or Anthropocene extinction), has resulted in a biodiversity crisis being driven by human activities which push beyond the planetary boundaries and so far has proven irreversible. Even though permanent global species loss is a more dramatic and tragic phenomenon than regional changes in species composition, even minor changes from a healthy stable state can have dramatic influence on the food web and the food chain insofar as reductions in only one species can adversely aff ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ecology
Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overlaps with the closely related sciences of biogeography, evolutionary biology, genetics, ethology, and natural history. Ecology is a branch of biology, and it is not synonymous with environmentalism. Among other things, ecology is the study of: * The abundance, biomass, and distribution of organisms in the context of the environment * Life processes, antifragility, interactions, and adaptations * The movement of materials and energy through living communities * The successional development of ecosystems * Cooperation, competition, and predation within and between species * Patterns of biodiversity and its effect on ecosystem processes Ecology has practical applications in conservation biology, wetland management, natural res ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyploidy
Polyploidy is a condition in which the biological cell, cells of an organism have more than one pair of (Homologous chromosome, homologous) chromosomes. Most species whose cells have Cell nucleus, nuclei (eukaryotes) are diploid, meaning they have two sets of chromosomes, where each set contains one or more chromosomes and comes from each of two parents, resulting in pairs of homologous chromosomes between sets. However, some organisms are polyploid. Polyploidy is especially common in plants. Most eukaryotes have diploid somatic cells, but produce haploid gametes (eggs and sperm) by meiosis. A Ploidy, monoploid has only one set of chromosomes, and the term is usually only applied to cells or organisms that are normally diploid. Males of bees and other Hymenoptera, for example, are monoploid. Unlike animals, plants and multicellular algae have Biological life cycle, life cycles with two alternation of generations, alternating multicellular generations. The gametophyte generation is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Backcross
Backcrossing is a crossing of a hybrid with one of its parents or an individual genetically similar to its parent, to achieve offspring with a genetic identity closer to that of the parent. It is used in horticulture, animal breeding, and production of gene knockout organisms. Backcrossed hybrids are sometimes described with acronym "BC"; for example, an F1 hybrid crossed with one of its parents (or a genetically similar individual) can be termed a BC1 hybrid, and a further cross of the BC1 hybrid to the same parent (or a genetically similar individual) produces a BC2 hybrid. Plants Advantages * If the recurrent parent is an elite genotype, at the end of the backcrossing programme, an elite genotype is recovered. * As no "new" recombination results, the elite combination is not lost. Disadvantages * It works poorly for quantitative traits. * It is more restricted for recessive traits. * In practice, sections of genome from the nonrecurrent parents are often still present ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evidence For Speciation By Reinforcement
Reinforcement is a process within speciation where natural selection increases the reproductive isolation between two populations of species by reducing the production of hybrids. Evidence for speciation by reinforcement has been gathered since the 1990s, and along with data from comparative studies and laboratory experiments, has overcome many of the objections to the theory. Differences in behavior or biology that inhibit formation of hybrid zygotes are termed prezygotic isolation. Reinforcement can be shown to be occurring (or to have occurred in the past) by measuring the strength of prezygotic isolation in a sympatric population in comparison to an allopatric population of the same species. Comparative studies of this allow for determining large-scale patterns in nature across various taxa. Mating patterns in hybrid zones can also be used to detect reinforcement.Daniel J. Howard (1993). Reinforcement: origin, dynamics and fate of an evolutionary hypothesis. In: Harrison, R. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reinforcement
In behavioral psychology, reinforcement is a consequence applied that will strengthen an organism's future behavior whenever that behavior is preceded by a specific antecedent stimulus. This strengthening effect may be measured as a higher frequency of behavior (e.g., pulling a lever more frequently), longer duration (e.g., pulling a lever for longer periods of time), greater magnitude (e.g., pulling a lever with greater force), or shorter latency (e.g., pulling a lever more quickly following the antecedent stimulus). The model of self-regulation has three main aspects of human behavior, which are self-awareness, self-reflection, and self-regulation. Reinforcements traditionally align with self-regulation. The behavior can be influenced by the consequence but behavior also needs antecedents. There are four types of reinforcement: positive reinforcement, negative reinforcement, extinction, and punishment. Positive reinforcement is the application of a positive reinforcer. Nega ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Annual Review Of Ecology And Systematics
The ''Annual Review of Ecology, Evolution, and Systematics'' is an annual scientific journal published by Annual Reviews. The journal was established in 1970 as the ''Annual Review of Ecology and Systematics'' and changed its name beginning in 2003. It publishes invited review articles on topics considered to be timely and important in the fields of ecology, evolutionary biology, and systematics. As of 2022, ''Journal Citation Reports'' gave the journal a 2021 impact factor of 14.340, ranking it third of 173 journals in the "Ecology" category and third of 51 journals in "Evolutionary Biology". History The ''Annual Review of Ecology and Systematics'' was first published in 1970, with Richard F. Johnston as its first editor. In 1975 it began publishing biographies of notable ecologists in the prefatory chapter. In 2003, its name was changed to its current form, the ''Annual Review of Ecology, Evolution, and Systematics''. It defines its scope as covering significant developments ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nick Barton
Nicholas Hamilton Barton (born 30 August 1955) is a British evolutionary biologist. Education Barton was educated at Peterhouse, Cambridge where he graduated with a first-class degree in Biological Sciences (Cambridge) in 1976 and gained his PhD supervised by Godfrey Hewitt at the University of East Anglia in 1979. Career After a brief spell as a lab demonstrator at the University of Cambridge, Barton became a Lecturer at the Department of Genetics and Biometry, University College London, in 1982. Professor Barton is best known for his work on hybrid zones, often using the toad '' Bombina bombina'' as a study organism, and for extending the mathematical machinery needed to investigate multilocus genetics, a field in which he worked in collaboration with Michael Turelli. Research questions he has investigated include: the role of epistasis, the evolution of sex, speciation, and the limits on the rate of adaptation. Barton moved to the University of Edinburgh in 1990, where h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cline (biology)
In biology, a cline (from the Greek κλίνειν ''klinein'', meaning "to lean") is a measurable gradient in a single character (or biological trait) of a species across its geographical range. First coined by Julian Huxley in 1938, the "character" of the cline referred to is usually genetic (e.g. allele frequency, blood type), or phenotypic (e.g. body size, skin pigmentation). Clines can show smooth, continuous gradation in a character, or they may show more abrupt changes in the trait from one geographic region to the next. A cline refers to a spatial gradient in a specific, singular trait, rather than a collection of traits; a single population can therefore have as many clines as it has traits, at least in principle. Additionally, Huxley recognised that these multiple independent clines may not act in concordance with each other. For example, it has been observed that in Australia, birds generally become smaller the further towards the north of the country they are found. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Denisovans
The Denisovans or Denisova hominins ) are an extinct species or subspecies of archaic human that ranged across Asia during the Lower and Middle Paleolithic. Denisovans are known from few physical remains and consequently, most of what is known about them comes from DNA evidence. No formal species name has been established pending more complete fossil material. The first identification of a Denisovan individual occurred in 2010, based on mitochondrial DNA (mtDNA) extracted from a juvenile female finger bone excavated from the Siberian Denisova Cave in the Altai Mountains in 2008. Nuclear DNA indicates close affinities with Neanderthals. The cave was also periodically inhabited by Neanderthals, but it is unclear whether Neanderthals and Denisovans ever cohabited in the cave. Additional specimens from Denisova Cave were subsequently identified, as was a single specimen from the Baishiya Karst Cave on the Tibetan Plateau. DNA evidence suggests they had dark skin, eyes, and ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allopatric Speciation
Allopatric speciation () – also referred to as geographic speciation, vicariant speciation, or its earlier name the dumbbell model – is a mode of speciation that occurs when biological populations become geographically isolated from each other to an extent that prevents or interferes with gene flow. Various geographic changes can arise such as the movement of continents, and the formation of mountains, islands, bodies of water, or glaciers. Human activity such as agriculture or developments can also change the distribution of species populations. These factors can substantially alter a region's geography, resulting in the separation of a species population into isolated subpopulations. The vicariant populations then undergo genetic changes as they become subjected to different selective pressures, experience genetic drift, and accumulate different mutations in the separated populations' gene pools. The barriers prevent the exchange of genetic information between ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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