|
Linanthus Parryae
''Linanthus parryae'' is a species of flowering plant in the phlox family known by the common name sandblossoms. It is native to the western United States, growing in states including Oregon, Idaho, Wyoming, California, Nevada, Arizona, New Mexico, and Colorado. In California, it grows in several regions from the Central Valley to the Sierra Nevada foothills and the Mojave Desert. It occurs in sandy, open, flat areas. This is a petite annual herb producing short stems just a few centimeters tall surrounded by hairy, needle-lobed leaves. The inflorescence, which often appears to sit directly on the ground tucked amidst the leaves, is a cluster of funnel-shaped flowers about a centimeter wide. The flowers are self-incompatible and are cross-pollinated exclusively by Melyrid beetle, ''Trichochorous'' sp.ref name="Schemske & Bierzychudek 2001">Schemske, D. W. & P. Bierzychudek. (2001)Perspective: Evolution of flower color in the desert annual ''Linanthus parryae'': Wright revisited. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asa Gray
Asa Gray (November 18, 1810 – January 30, 1888) is considered the most important American botanist of the 19th century. His ''Darwiniana'' was considered an important explanation of how religion and science were not necessarily mutually exclusive. Gray was adamant that a genetic connection must exist between all members of a species. He was also strongly opposed to the ideas of hybridization within one generation and special creation in the sense of its not allowing for evolution. He was a strong supporter of Darwin, although Gray's theistic evolution was guided by a Creator. As a professor of botany at Harvard University for several decades, Gray regularly visited, and corresponded with, many of the leading natural scientists of the era, including Charles Darwin, who held great regard for him. Gray made several trips to Europe to collaborate with leading European scientists of the era, as well as trips to the southern and western United States. He also built an extensive ne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carl Epling
Carl Clawson Epling (15 April 1894 – 17 November 1968) was an American botanist and taxonomist. He is best known for being the major authority on the Lamiaceae (mint family) of the Americas from the 1920s to the 1960s. In his later years he also developed an interest in genetics. University of California: In Memoriam − Carl Clawson Epling, Botany: UC Los Angeles December 1970. History Epling obtained his B.A. from the College of Agriculture at in 1921. He received his M.A. in 1923 and Ph.D. in 1924 from |
Plant Models
Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclude the fungi and some algae, as well as the prokaryotes (the archaea and bacteria). By one definition, plants form the clade Viridiplantae (Latin name for "green plants") which is sister of the Glaucophyta, and consists of the green algae and Embryophyta (land plants). The latter includes the flowering plants, conifers and other gymnosperms, ferns and their allies, hornworts, liverworts, and mosses. Most plants are multicellular organisms. Green plants obtain most of their energy from sunlight via photosynthesis by primary chloroplasts that are derived from endosymbiosis with cyanobacteria. Their chloroplasts contain chlorophylls a and b, which gives them their green color. Some plants are parasitic or mycotrophic and have lost the ability ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linanthus
''Linanthus'' is a genus of annual and perennial plants in the phlox family Polemoniaceae. The species are found in western North America and in Chile, with the greatest diversity in California. The stems are erect, with multiple branches arising directly from the base, and grow 2–15 cm tall. The leaves are stem-like (''cauline'') and opposite, with shapes ranging from entire to palmately lobed, the 3-9 lobes being linear to lanceolate or spatulate. Flowers have a tubular calyx, and the corolla may be funnel- or bell-shaped, or . The genus name is from the Greek for "flax flower", since the flowers superficially resemble those of flax. The genus has recently been split, with many of the species formerly included now transferred to the genus '' Leptosiphon'' (Jepson Manual). ;Selected species * '' Linanthus bellus'' (Gray) Greene * '' Linanthus bigelovii'' (A. Gray) Greene * '' Linanthus concinnus'' Milliken * '' Linanthus demissus'' (A. Gray) Greene * '' Linanthus dian ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shifting Balance Theory
The shifting balance theory is a theory of evolution proposed in 1932 by Sewall Wright, suggesting that adaptive evolution may proceed most quickly when a population divides into subpopulations with restricted gene flow. The name of the theory is borrowed from Wright's metaphor of fitness landscapes (evolutionary landscapes), attempting to explain how a population may move across an adaptive valley to a higher adaptive peak. According to the theory, this movement occurs in three steps: #Genetic drift allows a locally adapted subpopulation to move across an adaptive valley to the base of a higher adaptive peak. #Natural selection will move the subpopulation up the higher peak. #This new superiorly adapted subpopulation may then expand its range (biology), range and outcompete or interbreed with other subpopulations, causing the spread of new adaptations and movement of the global population toward the new fitness peak. Although shifting balance theory has been influential in evol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isolation By Distance
Isolation by distance (IBD) is a term used to refer to the accrual of local genetic variation under geographically limited dispersal. The IBD model is useful for determining the distribution of gene frequencies over a geographic region. Both dispersal variance and migration probabilities are variables in this model and both contribute to local genetic differentiation. Isolation by distance is usually the simplest model for the cause of genetic isolation between populations. Evolutionary biologists and population geneticists have been exploring varying theories and models for explaining population structure. Yoichi Ishida compares two important theories of isolation by distance and clarifies the relationship between the two. According to Ishida, Sewall Wright's isolation by distance theory is termed ecological isolation by distance while Gustave Malécot's theory is called genetic isolation by distance. Isolation by distance is distantly related to speciation. Multiple types of isol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Natural Selection
Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Charles Darwin popularised the term "natural selection", contrasting it with selective breeding, artificial selection, which in his view is intentional, whereas natural selection is not. Genetic diversity, Variation exists within all populations of organisms. This occurs partly because random mutations arise in the genome of an individual organism, and their offspring can inherit such mutations. Throughout the lives of the individuals, their genomes interact with their environments to cause variations in traits. The environment of a genome includes the molecular biology in the Cell (biology), cell, other cells, other individuals, populations, species, as well as the abiotic environment. Because individuals with certain variants of the trait tend ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genetic Drift
Genetic drift, also known as allelic drift or the Wright effect, is the change in the 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. 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 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 Motoo Kimura rekindled the debate with his neutral theory of molecular evolution, which claims that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polymorphism (biology)
In biology, polymorphism is the occurrence of two or more clearly different morphs or forms, also referred to as alternative ''phenotypes'', in the population of a species. To be classified as such, morphs must occupy the same habitat at the same time and belong to a panmictic population (one with random mating). Ford E.B. 1965. ''Genetic polymorphism''. Faber & Faber, London. Put simply, polymorphism is when there are two or more possibilities of a trait on a gene. For example, there is more than one possible trait in terms of a jaguar's skin colouring; they can be light morph or dark morph. Due to having more than one possible variation for this gene, it is termed 'polymorphism'. However, if the jaguar has only one possible trait for that gene, it would be termed "monomorphic". For example, if there was only one possible skin colour that a jaguar could have, it would be termed monomorphic. The term polyphenism can be used to clarify that the different forms arise from the s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theodosius Dobzhansky
Theodosius Grigorievich Dobzhansky (russian: Феодо́сий Григо́рьевич Добржа́нский; uk, Теодо́сій Григо́рович Добржа́нський; January 25, 1900 – December 18, 1975) was a prominent Russian-American geneticist and evolutionary biologist, and a central figure in the field of evolutionary biology for his work in shaping the modern synthesis. Born in the Russian Empire, Dobzhansky emigrated to the United States in 1927, aged 27. He was a distant relation of the Russian writer Feodor Dostoevsky. His 1937 work ''Genetics and the Origin of Species'' became a major influence on the modern synthesis. He was awarded the US National Medal of Science in 1964 and the Franklin Medal in 1973. Biography Early life Dobzhansky was born on January 25, 1900, in Nemirov, Russian Empire (now Nemyriv, Ukraine), the only child of Grigory Dobzhansky, a mathematics teacher, and Sophia Voinarsky. He was given a rare name, Theodosius, bec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harlan Lewis
Frank Harlan Lewis (January 8, 1919 – December 12, 2008) was an American botanist, geneticist, taxonomist, systematist, and evolutionist who worked primarily with plants in the genus ''Clarkia''. He is best known for his theories of "catastrophic selection" and " saltational speciation", which are closely aligned with the concepts of quantum evolution and sympatric speciation. The concepts were first articulated in 1958 by Lewis and Peter H. Raven, and later refined in a 1962 paper by Lewis in which he coined the term "catastrophic selection". In 1966, he referred to the same mechanism as "saltational speciation". Lewis was Dean of Life Sciences at the University of California, Los Angeles from 1962 to 1981, a Fellow of the American Association for the Advancement of Science (1955), recipient of a Guggenheim Fellowship (1955), president of the Pacific Division of the Botanical Society of America (1959), president of the Society for the Study of Evolution (1961), president of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sewall Wright
Sewall Green Wright FRS(For) Honorary FRSE (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 Elizabeth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
.jpg "Click for more on -> Asa Gray")
