Reconnection and Rates of Speciation

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Chemical speciation and extractability of Zn, Cu and Cd in two contrasting biosolids-amended clay soils X.L. Qiao a , Y.M. Luo a, * , P. Christie b , M.H. Wong c a Laboratory of Material Cycling in the Pedosphere, Institute of Soil Science, Academia Sinica, P.O. Box 821, Nanjing 210008, China b Agricultural and Environmental Science Department, Queen’s University Belfast, Newforge Lane, Belfast BT9 5PX, UK c Department of Biology, Hong Kong Baptist University, Kowloon, Hong Kong Abstract An incubation experiment was conducted to study the chemical speciation and extractability of three heavy metals in two contrasting biosolids-amended clay soils. One was a paddy soil of pH 7.8 and the other was a red soil of pH 4.7 collected from a fallow field. Anaerobically digested biosolids were mixed with each of the two soils at three rates: 20, 40 and 60 g kg À1 soil (DM basis), and unamended controls were also prepared. The biosolids-amended and control soils were incubated at 70% of water holding capacity at 25 °C for 50 days. Separate subsamples were extracted with three single extractants and a three-step sequential extraction procedure representing acetic acid (HOAc)-soluble, reducible and oxidisable fractions to investigate the extractability and speciation of the heavy metals. As would be expected, there were good relationships between biosolids application rate and metal concentrations in the biosolids-amended soils. The three heavy metals had different extractabilities and chemical speciation in the two biosolids-amended soils. Ethylene diamine tetraacetic acid extracted more Cu, Zn and Cd than did the other two single extractants. The oxi- disable fraction was the major fraction for Cu in both biosolids-amended soils and the HOAc-soluble and reducible fractions accounted for most of the Zn. In contrast, Cd was present mainly in the reducible fraction. The results are discussed in relation to the mobility and bioavailability of the metals in polluted soils. Ó 2002 Elsevier Science Ltd. All rights reserved. Keywords: Sewage sludge; Heavy metals; Sequential extraction; Single extraction; Speciation 1. Introduction With continuing industrial development, urbaniza- tion and a growing human population, large quantities (>300 000 t dry weight per year) of biosolids are pro- duced in China but the proportion of wastewater cur- rently subjected to treatment processes is only slightly above 4.5% (Zhou et al., 1999). A rapid increase in the number of wastewater treatment plants with consequent improvements in water quality can be expected over the next several decades as government and the general public become more aware of environmental issues. Bio- solids contain plant nutrients in addition to potentially toxic contaminants, and can therefore be used to recycle nutrients during disposal. The major disposal options currently available include application to agricultural land, incineration, land reclamation, landfill, forestry and application to ‘dedicated’ land (Matthews, 1992). Dumping at sea has been prohibited in many countries including China. Land filling and incineration are un- popular because of the high cost and environmental hazards involved. Land application has become more popular because of the relatively low cost and the ben- efits of recycling of nutrients and organic matter. Despite the potential benefits, there is still much concern about land Reconnection and Rates of Speciation Reconnection and Rates of Speciation Bởi: OpenStaxCollege Speciation occurs over a span of evolutionary time, so when a new species arises, there is a transition period during which the closely related species continue to interact Reconnection After speciation, two species may recombine or even continue interacting indefinitely Individual organisms will mate with any nearby individual who they are capable of breeding with An area where two closely related species continue to interact and reproduce, forming hybrids, is called a hybrid zone Over time, the hybrid zone may change depending on the fitness of the hybrids and the reproductive barriers ([link]) If the hybrids are less fit than the parents, reinforcement of speciation occurs, and the species continue to diverge until they can no longer mate and produce viable offspring If reproductive barriers weaken, fusion occurs and the two species become one Barriers remain the same if hybrids are fit and reproductive: stability may occur and hybridization continues Art Connection 1/5 Reconnection and Rates of Speciation After speciation has occurred, the two separate but closely related species may continue to produce offspring in an area called the hybrid zone Reinforcement, fusion, or stability may result, depending on reproductive barriers and the relative fitness of the hybrids If two species eat a different diet but one of the food sources is eliminated and both species are forced to eat the same foods, what change in the hybrid zone is most likely to occur? Hybrids can be either less fit than the parents, more fit, or about the same Usually hybrids tend to be less fit; therefore, such reproduction diminishes over time, nudging the two species to diverge further in a process called reinforcement This term is used because the low success of the hybrids reinforces the original speciation If the hybrids are as fit or more fit than the parents, the two species may fuse back into one species ([link]) Scientists have also observed that sometimes two species will remain separate but also continue to interact to produce some hybrid individuals; this is classified as stability because no real net change is taking place Varying Rates of Speciation Scientists around the world study speciation, documenting observations both of living organisms and those found in the fossil record As their ideas take shape and as research reveals new details about how life evolves, they develop models to help explain rates of speciation In terms of how quickly speciation occurs, two patterns are currently observed: gradual speciation model and punctuated equilibrium model In the gradual speciation model, species diverge gradually over time in small steps In the punctuated equilibrium model, a new species undergoes changes quickly from the parent species, and then remains largely unchanged for long periods of time afterward ([link]) This early change model is called punctuated equilibrium, because it begins with a punctuated or periodic change and then remains in balance afterward While punctuated equilibrium suggests a faster tempo, it does not necessarily exclude gradualism Art Connection 2/5 Reconnection and Rates of Speciation In (a) gradual speciation, species diverge at a slow, steady pace as traits change incrementally In (b) punctuated equilibrium, species diverge quickly and then remain unchanged for long periods of time Which of the following statements is false? Punctuated equilibrium is most likely to occur in a small population that experiences a rapid change in its environment Punctuated equilibrium is most likely to occur in a large population that lives in a stable climate Gradual speciation is most likely to occur in species that live in a stable climate Gradual speciation and punctuated equilibrium both result in the divergence of species The primary influencing factor on changes in speciation rate is environmental conditions Under some conditions, selection occurs quickly or radically Consider a species of snails that had been living with the same basic form for many thousands of years Layers of their fossils would appear similar for a long time When a change in the environment takes place—such as a drop in the water level—a small number of organisms are separated from the rest in a brief period of time, essentially forming one large and one tiny population The tiny population faces new environmental conditions Because its gene pool quickly became so small, any variation that surfaces and that aids in surviving the new conditions becomes the predominant form 3/5 Reconnection and Rates of Speciation Link to Learning Visit this website to continue the speciation story of the snails Section Summary Speciation is not a precise division: overlap between closely related species can occur in areas called hybrid zones Organisms reproduce with other similar organisms The fitness of these hybrid offspring can affect the evolutionary path of ...Concentrations and chemical speciations of Cu, Zn, Pb and Cr of urban soils in Nanjing, China Ying Lu a,b, * , Zitong Gong a , Ganlin Zhang a , Wolfgang Burghardt c a Institute of Soil Science, Academia Sinica, Nanjing 210008, PR China b College of Resources and Environmental Science, South China Agricultural University, Guangzhou 510642, PR China c Department of Applied Soil Science, University of Essen, 45141 Essen, Germany Abstract About 150 soil samples from 20 urban and 3 non-urban soil profiles in Nanjing were analyzed for total concentrations of Cu, Zn, Pb and Cr using ICP spectrometry. The Cu, Zn, Pb and Cr of 23 urban and non-urban topsoils (A horizon soils) were sequentially extracted into 5 fractions according to the method of Tessier [Anal. Chem. 51 (1979) 844]. Total Cu, Zn, Pb and Cr concentrations of the urban soils were 84.7 (48.1–139.7), 66.1 (12.2 – 869.4), 162.6 (57.7 – 851.6) and 107.3 (36.3– 472.6) mg kg À 1 , respectively. The soils were polluted with Cu, Zn and Cr to some extent and heavily polluted with Pb. For 20 urban topsoils, the Cu, Zn, Pb and Cr were dominated by the residual fraction and were least present in exchangeable fraction. On average, the order of Cr, Cu in each fraction was residual (92.9%, 66.1%)Horganic (4.2%, 23.4%)>Fe–Mn oxide (2.7%, 5.4%)>carbonate (0.2%, 4.7%)>exchangeable (0.04%, 0.38%), Zn followed the order residual (60.0%)HFe – Mn oxides (19.1%)>carbonate (11.6%)>organic (8.8%)>exchangeable (0.5%), Pb was residual (56.8%)>Fe – Mn oxide (30.9%)Horganic (6.3%)>carbonate (5.2%)>exchangeable (0.8%). The percentage of residual Cu and Zn decreased with the increase of total Cu and Zn concentrations. The proportion of residual Pb increased with the increase of total P. The mobility and bioavailability of heavy metals were Pb>Zn>Cu>Cr. Cu, Zn and Pb were more mobile and bioavailable in the urban than in the non- urban soils; however, Cr was similar. D 2003 Elsevier Science B.V. All rights reserved. Keywords: Heavy metals; Chemical speciations; Urban soils; Nanjing, China 0016-7061/03/$ - see front matter D 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0016-7061(03)00079-X * Corresponding author. College of Resources and Environmental Science, South China Agricultural University, Guangzhou 510642, PR China. Tel.: +86-20-85280295. E-mail address: luying@scau.edu.cn (Y. Lu). www.elsevier.com/locate/geoderma Geoderma 115 (2003) 101–111 1. Introduction Heavy metal contamination in urban soils can be harmful to the biota and human beings, and extensive investigations have been carried out recently in some countries and regio ns (Culbard et al., 1988; Thornton, 1991; Weiss et al., 1994; Chon et al., 1995; Markus and McBrantney, 1996; Chen et al., 1997; Kasimov and Lychagin, 1998; Lavado et al., 1998; Stroganova et al., 1998; Wilcke et al., 1998, 1999). Total analysis may give information concerning possible enrichment of the soil with heavy metals, but it is generally recognized that it is the chemical form of a metal in the soil that determines its mobilization capacity and behavior in the environment. Sequential extraction provides information about the differ- entiation of the relative bonding strength of metal on various solid phases and about their potential reactivity under different physicochemical Development of Rates of Postage, by A. D. Smith Project Gutenberg's The Development of Rates of Postage, by A. D. Smith This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at www.gutenberg.net Title: The Development of Rates of Postage An Historical and Analytical Study Author: A. D. Smith Contributor: Herbert Samuel Release Date: September 28, 2010 [EBook #34011] Language: English Character set encoding: ISO-8859-1 *** START OF THIS PROJECT GUTENBERG EBOOK DEVELOPMENT OF RATES OF POSTAGE *** Produced by Simon Gardner, Adrian Mastronardi, The Philatelic Digital Library Project at http://www.tpdlp.net and the Online Distributed Proofreading Team at http://www.pgdp.net Transcriber's Notes This is a Plain Text version. It uses the Latin-1 character set. Development of Rates of Postage, by A. D. Smith 1 The following are used to represent special characters and marks: [~d] [~r] indicates a tilde above d, r [p=] indicates a line below p [=o] [=co] [=xon] indicate an overline extending 1, 2 & 3 characters [^p] indicates an inverted breve above p [oe] indicates an oe ligature Italic typeface in the original is indicated with underscores. Bold typeface in the original is indicated by UPPER CASE. Small capital typeface in the original is indicated by UPPER CASE. There are a large number of footnotes which have been numbered sequentially and grouped together at end of the book. There are numerous quotations from documents in German, French and archaic English which use many abbreviations, variant spellings and inconsistent spellings. These are retained, unless an obvious typo correction is listed at the end of this document. * * * * * STUDIES IN ECONOMICS AND POLITICAL SCIENCE. EDITED BY THE HON. W. PEMBER REEVES, PH.D., Director of the London School of Economics and Political Science. No. 50 in the Series of Monographs by writers connected with the London School of Economics and Political Science. THE DEVELOPMENT OF RATES OF POSTAGE * * * * * THE DEVELOPMENT OF RATES OF POSTAGE AN HISTORICAL AND ANALYTICAL STUDY BY A. D. SMITH, B.Sc. (ECON.) OF THE SECRETARY'S OFFICE, GENERAL POST OFFICE, LONDON WITH AN INTRODUCTION BY THE RIGHT HON. HERBERT SAMUEL, M.P. POSTMASTER-GENERAL 1910-14 AND 1915-16 LONDON: GEORGE ALLEN & UNWIN LTD. RUSKIN HOUSE 40 MUSEUM STREET, W.C. 1 [Thesis approved for the Degree of Doctor of Science (Economics) in the University of London] First published in 1917 (All rights reserved) PREFACE Development of Rates of Postage, by A. D. Smith 2 This study, which was prepared primarily as a Research Studentship Report for the University of London, is intended to be a contribution to the history of rates of postage, and an attempt to ascertain the principles, economic or otherwise, on which they are and have been based. The Postmaster-General accorded me permission to consult the official records at the General Post Office, London, and through this courtesy I have been enabled to include a detailed examination of the economic aspect of the rates in the inland service in this country, and to place in the Appendix After reading this chapter, students should be able to: • Define dollar return and rate of return. • Define risk and calculate the expected rate of return, standard deviation, and coefficient of variation for a probability distribution. • Specify how risk aversion influences required rates of return. • Graph diversifiable risk and market risk; explain which of these is relevant to a well-diversified investor. • State the basic proposition of the Capital Asset Pricing Model (CAPM) and explain how and why a portfolio’s risk may be reduced. • Explain the significance of a stock’s beta coefficient, and use the Security Market Line to calculate a stock’s required rate of return. • List changes in the market or within a firm that would cause the required rate of return on a firm’s stock to change. • Identify concerns about beta and the CAPM. • Explain how stock price volatility is more likely to imply risk than earnings volatility. Learning Objectives: 5 - 1 Chapter 5 Risk and Rates of Return LEARNING OBJECTIVES Risk analysis is an important topic, but it is difficult to teach at the introductory level. We just try to give students an intuitive overview of how risk can be defined and measured, and leave a technical treatment to advanced courses. Our primary goals are to be sure students understand (1) that investment risk is the uncertainty about returns on an asset, (2) the concept of portfolio risk, and (3) the effects of risk on required rates of return. What we cover, and the way we cover it, can be seen by scanning Blueprints, Chapter 5. For other suggestions about the lecture, please see the “Lecture Suggestions” in Chapter 2, where we describe how we conduct our classes. DAYS ON CHAPTER: 3 OF 58 DAYS (50-minute periods) Lecture Suggestions: 5 - 2 LECTURE SUGGESTIONS 5-1 a. The probability distribution for complete certainty is a vertical line. b. The probability distribution for total uncertainty is the X-axis from -∞ to +∞. 5-2 Security A is less risky if held in a diversified portfolio because of its negative correlation with other stocks. In a single-asset portfolio, Security A would be more risky because σ A > σ B and CV A > CV B . 5-3 a. No, it is not riskless. The portfolio would be free of default risk and liquidity risk, but inflation could erode the portfolio’s purchasing power. If the actual inflation rate is greater than that expected, interest rates in general will rise to incorporate a larger inflation premium (IP) and as we shall see in Chapter 7 the value of the portfolio would decline. b. No, you would be subject to reinvestment rate risk. You might expect to “roll over” the Treasury bills at a constant (or even increasing) rate of interest, but if interest rates fall, your investment income will decrease. c. A U.S. government-backed bond that provided interest with constant purchasing power (that is, an indexed bond) would be close to riskless. The U.S. Treasury currently issues indexed bonds. 5-4 a. The expected return on a life insurance policy is calculated just as for a common stock. Each outcome is multiplied by its probability of occurrence, and then these products are summed. For example, suppose a 1-year term policy pays $10,000 at death, and the probability of the policyholder’s death in that year is 2 percent. Then, there is a 98 percent probability of zero return and a 2 percent probability of $10,000: Expected return = 0.98($0) + 0.02($10,000) = $200. This expected return could be compared to the premium Genome Biology 2007, 8:R21 comment reviews reports deposited research refereed research interactions information Open Access 2007Gazaveet al.Volume 8, Issue 2, Article R21 Research Patterns and rates of intron divergence between humans and chimpanzees Elodie Gazave * , Tomàs Marqués-Bonet * , Olga Fernando *† , Brian Charlesworth ‡ and Arcadi Navarro § Addresses: * Unitat de Biologia Evolutiva, Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, Carrer Dr Aiguader 88, 08003 Barcelona, Catalonia, Spain. † Instituto de Tecnologia Química e Biológica (ITQB), Universidade Nova de Lisboa, Av. da República (EAN) 2781-901 Oeiras, Lisboa, Portugal. ‡ Institute of Evolutionary Biology, University of Edinburgh, West Mains Road, Edinburgh, Scotland, EH7 3JT, UK. § Institucio Catalana de Recerca i Estudis Avancats (ICREA), Unitat de Biologia Evolutiva, Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, Carrer Dr Aiguader 88, 08003 Barcelona, Catalonia, Spain. Correspondence: Arcadi Navarro. Email: arcadi.navarro@upf.edu © 2007 Gazave et al.; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Primate intron divergence<p>An analysis of human-chimpanzee intron divergence shows strong correlations between intron length and divergence and GC-con-tent.</p> Abstract Background: Introns, which constitute the largest fraction of eukaryotic genes and which had been considered to be neutral sequences, are increasingly acknowledged as having important functions. Several studies have investigated levels of evolutionary constraint along introns and across classes of introns of different length and location within genes. However, thus far these studies have yielded contradictory results. Results: We present the first analysis of human-chimpanzee intron divergence, in which differences in the number of substitutions per intronic site (K i ) can be interpreted as the footprint of different intensities and directions of the pressures of natural selection. Our main findings are as follows: there was a strong positive correlation between intron length and divergence; there was a strong negative correlation between intron length and GC content; and divergence rates vary along introns and depending on their ordinal position within genes (for instance, first introns are more GC rich, longer and more divergent, and divergence is lower at the 3' and 5' ends of all types of introns). Conclusion: We show that the higher divergence of first introns is related to their larger size. Also, the lower divergence of short introns suggests that they may harbor a relatively greater proportion of regulatory elements than long introns. Moreover, our results are consistent with the presence of functionally relevant sequences near the 5' and 3' ends of introns. Finally, our findings suggest that other parts of introns may also be under selective constraints. Background Introns are neither neutrally evolving sequences nor junk DNA, as they were once considered to be. Increasing amounts of evidence show that they harbor a variety of untranslated RNAs, including microRNAs, small nucleolar RNAs, and guide RNAs for RNA editing [1]. Introns are also important for mRNA processing and transport [2]. Moreover, micro- array tiling experiments [3] have shown that a substantial Published: 19 February 2007 Genome Biology 2007, 8:R21 (doi:10.1186/gb-2007-8-2-r21) Received: 2 August 2006 Revised: 8 December 2006 Accepted: 19 February 2007 The electronic version of this article is the complete one and can be found online at http://genomebiology.com/2007/8/2/R21 R21.2 Genome Biology 2007, Volume 8, Issue 2, Article R21 Gazave et al. ... help explain rates of speciation In terms of how quickly speciation occurs, two patterns are currently observed: gradual speciation model and punctuated equilibrium model In the gradual speciation. .. surfaces and that aids in surviving the new conditions becomes the predominant form 3/5 Reconnection and Rates of Speciation Link to Learning Visit this website to continue the speciation story of. . .Reconnection and Rates of Speciation After speciation has occurred, the two separate but closely related species may continue to produce offspring in an area called