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Developmental Bias
In evolutionary biology, developmental bias refers to the production against or towards certain Ontogeny, ontogenetic trajectories which ultimately influence the direction and outcome of evolutionary change by affecting the rates, magnitudes, directions and limits of Phenotypic trait, trait evolution. Historically, the term was synonymous with developmental constraint, however, the latter has been more recently interpreted as referring solely to the negative role of development in evolution. The role of the embryo In modern evolutionary biology, the idea of developmental bias is embedded into a current of thought called ''Structuralism (biology), Structuralism'', which emphasizes the role of the organism as a ''causal'' force of evolutionary change. In the Structuralist view, phenotypic evolution is the result of the action of natural selection on previously ‘filtered’ variation during the course of ontogeny. It contrasts with the ''Functionalist'' (also “adaptationist”, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolutionary Biology
Evolutionary biology is the subfield of biology that studies the evolutionary processes such as natural selection, common descent, and speciation that produced the diversity of life on Earth. In the 1930s, the discipline of evolutionary biology emerged through what Julian Huxley called the Modern synthesis (20th century), modern synthesis of understanding, from previously unrelated fields of biological research, such as genetics and ecology, systematics, and paleontology. The investigational range of current research has widened to encompass the genetic architecture of adaptation, molecular evolution, and the different forces that contribute to evolution, such as sexual selection, genetic drift, and biogeography. The newer field of evolutionary developmental biology ("evo-devo") investigates how embryogenesis is controlled, thus yielding a wider synthesis that integrates developmental biology with the fields of study covered by the earlier evolutionary synthesis. Subfields ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geophilomorpha
Geophilomorpha is an order of centipedes commonly known as soil centipedes. The name "Geophilomorpha" is from Ancient Greek roots meaning "formed to love the earth." This group is the most diverse centipede order, with 230 genera. These centipedes are found nearly worldwide but are absent in Antarctica and most Arctic regions. Description Centipedes in this order are epimorphic, hatching with a full complement of segments. These centipedes each have an odd number of leg-bearing segments ranging from 27 (in the genus '' Schendylops'') to 191 (in the species '' Gonibregmatus plurimipes''). They are eyeless and blind, with long and narrow bodies, ranging from yellow to brown in color and from about 1 cm to 22 cm in length. They bear spiracles on all leg-bearing segments except the first and the last. The antennae have 14 segments and are usually slightly attenuated. Suborders and families This order is a monophyletic group including two suborders: the monophyletic Placodesmata, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. Other ways of defining species include their karyotype, DNA sequence, morphology (biology), morphology, behaviour, or ecological niche. In addition, palaeontologists use the concept of the chronospecies since fossil reproduction cannot be examined. The most recent rigorous estimate for the total number of species of eukaryotes is between 8 and 8.7 million. About 14% of these had been described by 2011. All species (except viruses) are given a binomial nomenclature, two-part name, a "binomen". The first part of a binomen is the name of a genus to which the species belongs. The second part is called the specific name (zoology), specific name or the specific ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolvability
Evolvability is defined as the capacity of a system for adaptive evolution. Evolvability is the ability of a population of organisms to not merely generate genetic diversity, but to generate '' adaptive'' genetic diversity, and thereby evolve through natural selection. In order for a biological organism to evolve by natural selection, there must be a certain minimum probability that new, heritable variants are beneficial. Random mutations, unless they occur in DNA sequences with no function, are expected to be mostly detrimental. Beneficial mutations are always rare, but if they are too rare, then adaptation cannot occur. Early failed efforts to evolve computer programs by random mutation and selection showed that evolvability is not a given, but depends on the representation of the program as a data structure, because this determines how changes in the program map to changes in its behavior. Analogously, the evolvability of organisms depends on their genotype–phenotype map. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Additive Genetic Variance
Genetic effects are broadly divided into two categories: additive and non-additive. Additive genetic effects occur where expression of more than one gene contributes to phenotype (or where alleles of a heterozygous gene both contribute), and the phenotypic expression of these gene(s) can be said to be the sum of these contributions. Non-additive effects involve dominance or epistasis, and cause outcomes that are not a sum of the contribution of the genes involved. Additive genetic effects are singularly important with regard to quantitative traits, as the sum of these effects informs the placement of a trait on the spectrum of possible outcomes. Quantitative traits are commonly polygenic (resulting from the effects of more than one locus). Heritability Broad sense heritability Variation in phenotypes across a population arises from the interaction between environmental variation and genetic variation between individuals. This can be stated mathematically as: VP = VE + VG ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Breeder’s Equation
Heritability is a statistic used in the fields of breeding and genetics that estimates the degree of ''variation'' in a phenotypic trait in a population that is due to genetic variation between individuals in that population. The concept of heritability can be expressed in the form of the following question: "What is the proportion of the variation in a given trait within a population that is ''not'' explained by the environment or random chance?" Other causes of measured variation in a trait are characterized as environmental factors, including observational error. In human studies of heritability these are often apportioned into factors from "shared environment" and "non-shared environment" based on whether they tend to result in persons brought up in the same household being more or less similar to persons who were not. Heritability is estimated by comparing individual phenotypic variation among related individuals in a population, by examining the association between individ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linkage Disequilibrium
Linkage disequilibrium, often abbreviated to LD, is a term in population genetics referring to the association of genes, usually linked genes, in a population. It has become an important tool in medical genetics and other fields In defining LD, it is important first to distinguish the two very different concepts, linkage disequilibrium and linkage (genetic linkage). Linkage disequilibrium refers to the association of genes ''in a population.'' Linkage, on the other hand, tells us whether genes are on the same chromosome ''in an individual''. There is no necessary relationship between the two. Genes that are closely linked may or may not be associated in populations. Looking at parents and offspring, if genes at closely linked loci are together in the parent then they will usually be together in the offspring. But looking at individuals in a population with no known common ancestry, it is much more difficult to see any relationships. To give a concrete, although imaginary, example i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantitative Genetics
Quantitative genetics is the study of quantitative traits, which are phenotypes that vary continuously—such as height or mass—as opposed to phenotypes and gene-products that are Categorical variable, discretely identifiable—such as eye-colour, or the presence of a particular biochemical. Both of these branches of genetics use the frequencies of different alleles of a gene in breeding populations (gamodemes), and combine them with concepts from simple Mendelian inheritance to analyze inheritance patterns across generations and descendant lines. While population genetics can focus on particular genes and their subsequent metabolic products, quantitative genetics focuses more on the outward phenotypes, and makes only summaries of the underlying genetics. Due to the continuous distribution of phenotypic values, quantitative genetics must employ many other statistical methods (such as the ''effect size'', the ''mean'' and the ''variance'') to link phenotypes (attributes) to gen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pleiotropy
Pleiotropy () is a condition in which a single gene or genetic variant influences multiple phenotypic traits. A gene that has such multiple effects is referred to as a ''pleiotropic gene''. Mutations in pleiotropic genes can impact several traits simultaneously, often because the gene product is used in various cell (biology), cells and affects different biological targets through shared signaling pathways. Pleiotropy can result from several distinct but potentially overlapping mechanisms, including gene pleiotropy, developmental biology, developmental pleiotropy, and selectional pleiotropy. Gene pleiotropy occurs when a gene product interacts with multiple proteins or catalyzes different reactions. Developmental pleiotropy refers to mutations that produce several phenotype, phenotypic effects during development. Selectional pleiotropy occurs when a single phenotype influences evolutionary fitness (biology), fitness in multiple ways (depending on factors such as age and sex). T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allometry
Allometry (Ancient Greek "other", "measurement") is the study of the relationship of body size to shape, anatomy, physiology and behaviour, first outlined by Otto Snell in 1892, by D'Arcy Thompson in 1917 in ''On Growth and Form'' and by Julian Huxley in 1932. Overview Allometry is a well-known study, particularly in statistical shape analysis for its theoretical developments, as well as in biology for practical applications to the differential growth rates of the parts of a living organism's body. One application is in the study of various insect species (e.g., Hercules beetles), where a small change in overall body size can lead to an enormous and disproportionate increase in the dimensions of appendages such as legs, antennae, or horns. The relationship between the two measured quantities is often expressed as a power law equation (allometric equation) which expresses a remarkable scale symmetry: : y = k x^a, or in a logarithmic form, : \log y = a \log x + \log k, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
