bluuebunny/crossref_metadata_2025 huggingface dataset:
Sex Ratios and Sex Allocation
Authors: Orzack Steven Hecht
Published: November 2020

Understanding the allocation of energy is the goal of the evolutionary analysis of sex allocation. Whether one is concerned with the relative sizes of male and female flower parts in plants like those discussed by Campbell (1998), the ratio of males and females in insects like those discussed by Orzack et al. (1991), or the relative sizes of male and female reproductive organs in hermaphroditic fish like those discussed by Leonard (1993), one is concerned with how energy allocated toward reproduction is apportioned into one sex as opposed to the other (or more in the case of some kinds of organisms). Here, the sexes are entities that at regular or irregular intervals produce gametes, some of which come together to produce zygotes. The abstract nature of this description underscores the degree to which there are common evolutionary aspects to all of these problems, despite the fact that the biological details involved are so diverse. One of the most influential and important agendas for evolutionary studies of sex allocation was laid out by Charnov (1982). He described the underlying evolutionary similarities between phenomena as diverse as sex change in shrimp and sex ratio in vertebrates like us. Even more important, he promoted sex allocation as a central evolutionary problem by describing how seemingly unrelated allocation problems could all be analyzed with a kind of mathematical approach elaborated by Shaw and Mohler (1953). I consider in turn four important examples of this approach. Shaw and Mohler’s goal was to understand the evolution of the proportions of males and females. This problem of the sex ratio was most famously addressed by Darwin in his 1871 book, The Descent of Man, and Selection in Relation to Sex, as well as by others in the subsequent decades. The most influential analysis is that of Fisher (1930); however, Carl Düsing, who worked in the 1880s, can rightly be regarded as the progenitor of modern sex ratio theory (see Edwards 1998).
The Evolutionary Ecology of Movement
Authors: Dingle Hugh , Holyoak Marcel
Published: November 2020

Organisms move, and their movement can take place by walking, swimming, or flying; via transport by another organism (phoresy); or by a vehicle such as wind or current (Dingle 1996). The functions of movement include finding food or mates, escaping from predators or deteriorating habitats, the avoidance of inbreeding, and the invasion and colonization of new areas. Virtually all life functions require at least some movement, so it is hardly surprising that organisms have evolved a number of structures, devices, and behaviors to facilitate it. The behavior of individuals while moving and the way this behavior is incorporated into life histories form one part of this chapter. This discussion focuses on the action of selection on the evolution of individual behavior, on how specific kinds of movement can be identified from the underlying behavior and physiology, and on the functions of the various movement behaviors. The other major part of our discussion focuses on the consequences of movement behaviors for the ecology and dynamics of populations. The pathways of the moving individuals within it can result in quite different outcomes for a population. First, movements may disperse the members of the population and increase the mean distances among them. The separation may be a result of paths more-or- less randomly chosen by organisms as they seek resources, or it may be a consequence of organisms avoiding one another. In contrast to dispersing them, movement may also bring individuals together either because they clump or congregate in the same habitat patch or because they actively aggregate through mutual attraction. Clumping can also lead to aggregation and mutually attracting social interactions. A classic example is the gregarious (aggregating) phase of the desert locust (Schistocerca gregaria), in which huge swarms of many millions of individuals first congregate in suitable habitats and then develop and retain cohesion based on mutual attraction. The foraging swarms make the locust a devastating agricultural pest over much of Africa and the Middle East (Farrow 1990; Dingle 1996). It is the aggregation of locusts that makes them such destructive pests; they would be far less harmful if the populations dispersed.
Ecological Character Displacement
Authors: Schluter Dolph
Published: November 2020

Ecological character displacement is phenotypic evolution wrought or maintained by resource competition between species. By resource competition, I mean the negative impact of one species (or individual) on another arising from depletion of shared resources. Character evolution driven by other mutually harmful interactions, such as intraguild predation or behavioral interference, is not included in the current definition of character displacement but perhaps should be in future. For the purposes of this chapter, however, character displacement is synonymous with the coevolution of resource competitors. The idea that competition between species has a significant impact on character evolution has a lively history. Prior to about 20 years ago, competition was seen as one of the major factors responsible for the evolution of species differences, particularly in traits affecting resource exploitation (e.g., body size, beak shape). The idea is seen again and again in the early literature not because it was rigorously established but because it so readily accounted for observed patterns of species differences in nature. Support for the idea began to slip soon afterward, however, as alternative hypotheses were developed and as it became clear that the quality of most of the available evidence was poor. More recently, the idea has become respectable again as evidence from several systems has become more solid. My goal in this chapter is to present an overview of some of this evidence and how it has affected our understanding of the process. I begin with a brief historical sketch of character displacement and the expectations from theory. I then present a few of the highlights emerging from observational studies of patterns suggesting character displacement, their limitations, and their implications. I follow with an overview of recent experimental work that complements studies of pattern but goes beyond them by testing novel predictions of character displacement hypotheses. I end with suggestions about where the most significant future discoveries lie. The history of ideas on competition and character divergence begins with Darwin (1859), who regarded interspecific competition for resources as a fundamental and ubiquitous agent of divergent natural selection: “Natural selection . . . leads to divergence of character, for more living beings can be supported on the same area the more they diverge in structure, habitats, and constitution”.
Mutualisms
Authors: Bronstein Judith L.
Published: November 2020

The unusual behavior of cleaner fish has attracted both popular and scientific curiosity since its discovery early in the 20th century. These fish apparently make their living by removing external parasites from “host” fishes of other species (some also remove bacteria or diseased and injured tissue). When they approach cleaners, hosts assume an unusual motionless posture that allows cleaners to feed from their scales, from their gill cavities, or even inside their mouths. For their trouble, cleaner fish get a meal, and hosts get a good cleaning. The interaction between cleaner fish and their hosts is generally classified as a mutualism, or mutually beneficial interaction between species. Stories about this and other mutualisms have become staples of nature documentaries and the popular literature and have helped lure many students into a lifetime of studying biology. From the perspective of evolutionary ecology, however, the cleaner-host relationship is anything but straightforward (Poulin and Grutter 1996). First, it is not at all clear that this interaction confers reciprocal fitness benefits. Despite several decades of effort, only one study has shown that cleaners significantly reduce hosts’ parasite loads (Grutter 1999), and none has yet demonstrated that reducing parasite loads increases host success. Since cleaners often gouge the host’s flesh, particularly when parasites are few, the interaction is often more costly than beneficial. Second, if cleaning does not confer an advantage, it is not evident why hosts should tolerate and even actively solicit cleaners’ attention. In fact, sometimes hosts lure cleaners only to eat them, but the conditions under which it might be beneficial for a host to doublecross its cleaners like this remain unexplored. Third, we don’t really understand how cleaning behaviors arose in the first place, considering that the first individuals that approached hosts to feed on parasites were very likely eaten. Despite this constraint, cleaning has apparently evolved multiple times; it is found in at least five families, in both marine and freshwater species, and in both the temperate zone and the tropics.
Introduction
Authors: Bonabeau Eric , Dorigo Marco , Theraulaz Guy
Published: November 2020

Insects that live in colonies, ants, bees, wasps, and termites, have fascinated naturalists as well as poets for many years. “What is it that governs here? What is it that issues orders, foresees the future, elaborates plans, and preserves equilibrium?,” wrote Maeterlinck [230]. These, indeed, are puzzling questions. Every single insect in a social insect colony seems to have its own agenda, and yet an insect colony looks so organized. The seamless integration of all individual activities does not seem to require any supervisor. For example, Leafcutter ants (Atta) cut leaves from plants and trees to grow fungi. Workers forage for leaves hundreds of meters away from the nest, literally organizing highways to and from their foraging sites [174]. Weaver ant (Oecophylla) workers form chains of their own bodies, allowing them to cross wide gaps and pull stiff leaf edges together to form a nest. Several chains can join to form a bigger one over which workers run back and forth. Such chains create enough force to pull leaf edges together. When the leaves are in place, the ants connect both edges with a continuous thread of silk emitted by a mature larva held by a worker [172, 174]. In their moving phase, army ants (such as Eciton) organize impressive hunting raids, involving up to 200,000 workers, during which they collect thousands of prey (see chapter 2, section 2.2.3) [52, 269, 282]. In a social insect colony, a worker usually does not perform all tasks, but rather specializes in a set of tasks, according to its morphology, age, or chance. This division of labor among nestmates, whereby different activities are performed simultaneously by groups of specialized individuals, is believed to be more efficient than if tasks were performed sequentially by unspecialized individuals [188, 272]. In polymorphic species of ants, two (or more) physically different types of workers coexist. For example, in Pheidole species, minor workers are smaller and morphologically distinct from major workers.
Division of Labor and Task Allocation
Authors: Bonabeau Eric , Dorigo Marco , Theraulaz Guy
Published: November 2020

Many species of social insects have a division of labor. The resilience of task allocation exhibited at the colony level is connected to the elasticity of individual workers. The behavioral repertoire of workers can be stretched back and forth in response to perturbations. A model based on response thresholds connects individual-level plasticity with colony-level resiliency and can account for some important experimental results. Response thresholds refer to likelihood of reacting to task-associated stimuli. Low-threshold individuals perform tasks at a lower level of stimulus than high-threshold individuals. An extension of this model includes a simple form of learning. Within individual workers, performing a given task induces a decrease of the corresponding threshold, and not performing the task induces an increase of the threshold. This double reinforcement process leads to the emergence of specialized workers, that is, workers that are more responsive to stimuli associated with particular task requirements, from a group of initially identical individuals. The fixed response threshold model can be used to allocate tasks in a multiagent system, in a way that is similar to market-based models, where agents bid to get resources or perform tasks. The response threshold model with learning can be used to generate differentiation in task performance in a multiagent system composed of initially identical entities. Task allocation in this case is emergent and more robust with respect to perturbations of the system than when response thresholds are fixed. An example application to distributed mail retrieval is presented. In social insects, different activities are often performed simultaneously by specialized individuals. This phenomenon is called division of labor [253, 272]. Simultaneous task performance by specialized workers is believed to be more efficient than sequential task performance by unspecialized workers [188, 253]. Parallelism avoids task switching, which costs energy and time. Specialization allows greater efficiency of individuals in task performance because they “know” the task or are better equipped for it. All social insects exhibit reproductive division of labor: only a small fraction of the colony, often limited to a single individual, reproduces.
Putting Social Sciences Together Again; An Introduction to the Volume
Authors: Kohler Timothy A.
Published: November 2020

We accept many definitions for games, most not so grandiose as those of Napoleon treated by Byron. Often when I demonstrate the simulation of Anasazi settlement discussed in chapter 7 of this volume someone will say, "This is just a game isn't it?" I'm happy to admit that it is, so long as our definition of games encompasses child's play—which teaches about and prepares for reality—and not just those frivolous pastimes of adults, which release them from it. This volume is based on and made possible by recent developments in the field of agent-based simulation. More than some dry computer science technology or another corporate software gambit, this technology is in fact provoking great interest in the possibilities of simulating social, spatial, and evolutionary dynamics in human and primate societies in ways that have not previously been possible. What is agent-based modeling? Models of this sort are sometimes also called individual-oriented, or distributed artificial intelligence- based. Action in such models takes place through agents, which are processes, however simple, that collect information about their environment, make decisions about actions based on that information, and act (Doran et al. 1994:200). Artificial societies composed of interacting collections of such agents allow controlled experiments (of the sort impossible in traditional social research) on the effects of tuning one behavioral or environmental parameter at a time (Epstein and Axtell 1996:1-20). Research using these models emphasizes dynamics rather than equilibria, distributed processes rather than systems-level phenomena, and patterns of relationships among agents rather than relationships among variables. As a result visualization is an important part of analysis, affording these approaches a sometimes gamelike and often immediately engaging quality. OK, I admit it—they're fun. Despite our emphasis on agent-based modeling, we do not mean to imply that it should displace, or is always superior to, systems-level models based on, for example, differential equations. On the contrary: te Boekhorst and Hemelrijk nicely demonstrate how these approaches may be complementary. Even more strongly, we do not argue that these activities should become, ahead of empirical research, the principal tool of social science.
Introduction
Authors: Meyer William B.
Published: November 2020

IN THE MID-1830s, the young Nathaniel Hawthorne sat reading "what once were newspapers"—a bound volume of New England gazettes ninety-odd years old. Comparing the daily life that they portrayed with his own, Hawthorne was struck by how different and how much more severe the weather appeared to have been in the past. "The cold was more piercing then, and lingered farther into the spring," he decided; "our fathers bore the brunt of more raging and pitiless elements than we"; "winter rushed upon them with fiercer storms than now—blocking up the narrow forest-paths, and overwhelming the roads. 1 He was not alone in thinking so. Another resident of Salem, Dr. Edward Holyoke, had been of the same opinion. In his later years, the doctor spoke as the classic authority on the weather, the Oldest Inhabitant. Born in 1728, he lived until 1829, the full span of the century that Hawthorne judged mostly at secondhand, and he had kept a daily temperature log for the better part of it. A newspaper in 1824 reported a general belief that the seasons were "more lamb-like" than in earlier times. An English visitor a few years later was frequently told that the climate was moderating. Cold and snowstorms had grown less intense and less frequent: such had been, wrote John Chipman Gray in the 1850s, "and is perhaps still a prevailing impression among the inhabitants of New-England." All the same, that impression of the century gone by was wrong. Gray, who maintained that the winters had not changed, also tried to explain why intelligent observers could have supposed that they had. On one point, he granted, they were correct. Certainly the effects of the weather were not what they had once been. But there was no evidence that a shift in the weather was responsible. Holyoke's own records, analyzed after his death, did not bear out his belief that winter cold and storms had weakened in his lifetime. As Gray pointed out, if the impact of weather on New Englanders had changed, it was because New England society had changed.
Principles and Practice of Solid-Phase Peptide Synthesis
Authors: Fields Gregg B. , Lauer-Fields Janelle L
Published: November 2020

Peptides play key structural and functional roles in biochemistry, pharmacology, and neurobiology, and are important probes for research in enzymology, immunology, and molecular biology. The amino acid building blocks can be among the 20 genetically encoded L-residues, or else unusual ones, and the sequences can be linear, cyclic, or branched. It follows that rapid, efficient, and reliable methodology for the chemical synthesis of these molecules is of utmost interest. A number of synthetic peptides are significant commercial or pharmaceutical products, ranging from the sweet dipeptide L-Asp-L-Phe-OMe (aspartame) to clinically used hormones such as oxytocin, adrenocorticotropic hormone, calcitonin, and gonadotropin releasing hormone (GnRH) super-agonists. Synthesis can lead to potent and selective new drugs by judicious substitutions that change functional groups and/or conformations of the parent peptide. These include introduction of N- or C-alkyl substituents, unnatural or D-amino acids, side-chain modifications including sulfate or phosphate groups or carbohydrate moieties, and constraints such as disulfide bridges between half-cystines or side-chain lactams between Lys and Asp or Glu. Commercially important products that evolved from such studies include protease inhibitors, such as captopril and other angiotensin converting enzyme (ACE) inhibitors, peptidomimetic HIV protease inhibitors, and the somatostatin analog lanreotide. Most of the biologically or medicinally important peptides which are the targets for useful structure-function studies by chemical synthesis comprise under 50 amino acid residues, but occasionally a synthetic approach can lead to important conclusions about small proteins (full or domains) in the 100-200 residue size range. Methods for synthesizing peptides are divided conveniently into two categories: solution (classical) and solid-phase pep tide synthesis (SPPS). The classical methods have evolved since the beginning of the twentieth century, and they are described amply in several reviews and books (Wünsch, 1974; Finn and Hofmann, 1976; Bodanszky and Bodanszky, 1984; Goodman et al, 2001). The solid-phase alternative was conceived and elaborated by R. B. Merrifield beginning in 1959, and has also been covered comprehensively (Erickson and Merrifield, 1976; Birr, 1978; Barany and Merrifield, 1979; Stewart and Young, 1984; Merrifield, 1986; Barany et al., 1987, 1988; Kent, 1988; Atherton and Sheppard, 1989; Fields and Noble, 1990; Barany and Albericio, 1991; Fields et al., 1992; Gutte, 1995; Fields, 1997; Lloyd-Williams et al., 1997; Chan and White, 2000; Kates and Albericio, 2000).
Mountain Climates of North America
Authors: Whiteman C. David
Published: November 2020

The basic climatic characteristics of the major mountain ranges in the United States—the Appalachians, the Coast Range, the Alaska Range, the Cascade Range, the Sierra Nevada, and the Rocky Mountains—can be described in terms of the four factors discussed in chapter 1. The mountains of North America extend latitudinally all the way from the Arctic Circle (66.5°N) to the tropic of Cancer (23.5°N) (figure 2.1). There are significant differences in day length and angle of solar radiation over this latitude belt that result in large seasonal and diurnal differences in the weather from north to south. Elevations in the contiguous United States extend from below sea level at Death Valley to over 14,000 ft (4270 m) in the Cascade Range, the Sierra Nevada, and the Rocky Mountains. Several prominent peaks along the Coast Range in Alaska and Canada (e.g., Mount St. Elias and Mount Logan) reach elevations above 18,000 ft (5486 m). Denali (20,320 ft or 6194 m) in the Alaska Range is the highest peak in North America. The highest peak in the Canadian Rockies is Mt. Robson, with an elevation of 12,972 ft (3954 m). The climates of the Coast Range, the Cascade Range, and the Sierra Nevada, all near the Pacific Ocean, are primarily maritime. The Appalachian Mountains of the eastern United States are subject to a maritime influence from the Atlantic Ocean and the Gulf of Mexico, but they are also affected by the prevailing westerly winds that bring continental climatic conditions. Only the climate of the Rocky Mountains, far from both the Pacific and Atlantic Oceans, is primarily continental. Each of the mountain ranges is influenced by regional circulations. For example, the Appalachians are exposed to the warm, moist winds brought northward by the Bermuda-Azores High and to the influence of the Gulf Stream. Similarly, the Coast Range feels the impact of the Pacific High, the Aleutian low, and the Japanese Current. A mountain range, depending on its size, shape, orientation, and location relative to air mass source regions, can itself affect the regional climate by acting as a barrier to regional flows.
Pressure and Winds
Authors: Whiteman C. David
Published: November 2020

Atmospheric pressure at a given point in the atmosphere is the weight of a vertical column of air above that level. Differences in pressure from one location to another cause both horizontal motions (winds) and vertical motions (convection and subsidence) in the atmosphere. Vertical motions, whether associated with high and low pressure centers or with other meteorological processes, are the most important motions for producing weather because they determine whether clouds and precipitation form or dissipate. The location of high and low pressure centers is a key feature on weather maps, providing information about wind direction, wind speed, cloud cover, and precipitation. Pressure-driven winds carry air from areas where pressure is high to areas where pressure is low. However, the winds do not blow directly from a high pressure center to a low pressure center. Because of the effects of the rotation of the earth and friction, winds blow clockwise out of a high pressure center and counterclockwise into a low pressure center in the Northern Hemisphere. These wind directions are reversed in the Southern Hemisphere. The strength of the wind is proportional to the pressure difference between the two regions. When the pressure difference or pressure gradient is strong, wind speeds are high; when the pressure gradient is weak, wind speeds are low. As air flows out of a high pressure center, air from higher in the atmosphere sinks to replace it. This subsidence produces warming and the dissipation of clouds and precipitation. As air converges in a low pressure center, it rises and cools. If the air is sufficiently moist, cooling can cause the moisture to condense and form clouds. Further lifting of the air can produce precipitation. Thus, rising pressure readings at a given location indicate the approach of a high pressure center and fair weather, whereas falling pressure readings indicate the approach of a low pressure center and stormy weather. The vertical motions caused by the divergence of air out of a high pressure center or the convergence of air into a low pressure center are generally weak, with air rising or sinking at a rate of several cm per second, and they cannot be measured by routine weather observations.
Fire Weather and Smoke Management
Authors: Whiteman C. David
Published: November 2020

Wildland fires consume large areas of forest and grasslands every year. Fires are described in terms of fire behavior, which includes rate of spread and fire intensity. A fire that spreads rapidly burns less of the available fuel per square unit of area than a fire that moves slowly and allows the flaming front a longer residence time. A fire with flames that reach only two feet above the ground produces less heat and is less destructive than an intense fire that crowns, that is, has long flames and burns at the top (i.e., crown) of the forest canopy (figure 13.1). Fire suppression activities are initiated when a wildfire threatens people, property, or natural areas that need protection. These activities include dropping water or chemicals on a fire and establishing a fire line around the fire. A fire line is a zone along a fire’s edge where there is little or no fuel available to the fire. Roads, cliffs, rivers, and lakes can be part of a fire line, or land can be cleared by firefighters. Backfires may be set within the fire line to burn toward the fire, widening the fire line and reducing the likelihood of the fire spreading beyond it (figures 13.2 and 13.3). Fires can cross a fire line if the intensity is high or if spotting occurs, that is, if the wind carries burning material (firebrands) beyond the fire and across the fire line (figure 13.4). A wildland fire can be very destructive, but it can also be beneficial and may be used by land resource managers to accomplish specific ecological objectives. For example, smaller fires can reduce the danger of a large catastrophic fire by burning off underbrush. Fire can also be used to prepare land for planting, to control the spread of disease or insect infestations, to benefit plant species that are dependent on fire, to influence plant succession, or to alter the nutrients in the soil. When a fire is used to manage land resources, it is called a prescribed fire.
Aerial Spraying
Authors: Whiteman C. David
Published: November 2020

Aircraft are used in a number of resource management operations, including fire suppression, seeding and fertilizing operations, and the application of pesticides to agricultural, forest, and rangelands. The objectives of any aerial application are to apply the material, either liquid or solid, to the target area safely, efficaciously, and economically and to avoid drift, that is, off-target displacement of the agents. Barry (1993) is a general reference for aerial spraying of forests. Picot and Kristmanson (1997) provide an overview of all aspects of this topic. Bache and Johnstone (1993) give a detailed description of spray meteorology. The emphasis in this chapter is on the role of meteorology in the aerial application of liquid pest control agents to manage plant, fungal, and animal pests in mountainous forested areas. The effectiveness of a spray operation depends on the timing of the operation relative to phenological conditions, the characteristics of the forest canopy or rangeland being targeted, the spray formulation, pilot skills and attitude, the aircraft type and spray equipment used, and weather conditions. Pest control agents are regulated by federal, state, and local agencies. Restrictions on the use of agents are specified on the product label and may include weather conditions. Drift reduces the efficacy of a spray operation and can have unintended and undesirable impacts on nontarget species, residences, and public areas near the target area. Although there is a driftable component in every spray operation, the drift potential is generally greater for liquids than for solids because the size of liquid droplets becomes smaller after release into the atmosphere, depending on the volatility of the substance itself, the aircraft and spray equipment used, and the meteorological conditions at the time of spraying. The smaller the droplets, the greater the potential for drift. Weather conditions have a significant impact on drift because wind speed and direction, temperature, humidity, and atmospheric stability affect the transport, diffusion, evaporation, settling, and deposition of both solid particles and liquid droplets. The collection of meteorological data and the use of professional weather forecasts are thus an integral part of a spraying operation.
Overview of Condensed Phase Methods
Authors: Martinho Simões José A. , da Piedade Manuel Minas
Published: November 2020

This part includes a discussion of the main experimental methods that have been used to study the energetics of chemical reactions and the thermodynamic stability of compounds in the condensed phase (solid, liquid, and solution). The only exception is the reference to flame combustion calorimetry in section 7.3. Although this method was designed to measure the enthalpies of combustion of substances in the gaseous phase, it has very strong affinities with the other combustion calorimetric methods presented in the same chapter. Most published enthalpies of formation and reaction in the condensed phase were determined by calorimetry (see databases indicated in appendix B). It is therefore not surprising that the discussion of calorimetric methods occupies a large fraction of part II. The heart of a calorimeter is the calorimeter proper (also called measuring system or sample cell), which contains the reaction vessel, where the chemical reaction or phase transition under study occurs. Sometimes the calorimeter proper coincides with the reaction vessel. For example, in the setup shown in figure 6.1a, which is typical of many combustion calorimeters, the reaction vessel is placed inside the calorimeter proper. In the arrangement of figure 6.1b, used in many reaction-solution calorimeters, the calorimeter proper is also the reaction vessel. Normally, a controlled-temperature jacket surrounds the calorimeter proper. Other parts besides thermometers, commonly found in calorimeters, are stirring, heating, cooling, and ignition devices. Some of these devices are placed inside the calorimeter proper or cross its boundaries and are also considered to be part of it. In modern instruments, the data acquisition and many steps of the calorimetric experiments are usually computer-controlled. Calorimeters of many different designs have been constructed and operated. However, these are all variations of a few basic categories. For example, based on the heat exchange mode between the calorimeter proper and the surrounding jacket, it is convenient to distinguish three main classes of calorimeters: adiabatic, heat conduction, and isoperibol. In a perfectly adiabatic calorimeter no heat is transferred between the calorimeter proper and the jacket (the corresponding heat flow rate Φ = dQ/dt = 0, where Q represents the heat exchanged and t is time).
Photocalorimetry
Authors: Martinho Simões José A. , da Piedade Manuel Minas
Published: November 2020

Most experimental techniques addressed in the present book are suitable for investigating the thermochemistry of thermally activated reactions, that is, those reactions whose activation barrier can be overcome by increasing the thermal energy of the reactants. This thermal energy, which is the average sum of molecular translational, rotational, and vibrational energies, can be changed by varying the temperature of the reactants. Some chemical reactions, however, do not occur by thermal activation. They require larger energy inputs—big enough to raise the electronic energy of at least one of the reactants and even induce the cleavage of a chemical bond. This “surgical” energy promotion is only attainable by electromagnetic radiation with a suitable wavelength. Visible light (420–700 nm) or ultraviolet radiation are typically used because the energies involved are in the same range of electronic excitation energies and of bond dissociation enthalpies, for example, a 700 nm photon corresponds to an energy of 170.9 kJ mol−1 (see conversion factors in appendix A). The reactions initiated by electromagnetic radiation are said to be photochemically activated. Note that only the initiation step may require the absorption of one or more photons (a photochemical reaction). Subsequent steps of the mechanism may be “dark reactions,” proceeding by thermal activation. The thermochemical study of photochemical or photochemically activated processes is not amenable to most of the calorimeters described in this book, simply because they do not include a suitable radiation source or the necessary auxiliary equipment to monitor the electromagnetic energy absorbed by the reaction mixture. However, it is not hard to conceive how a calorimeter from any of the classes mentioned in chapter 6 (adiabatic, isoperibol, or heat flow) could be modified to accommodate the necessary hardware and be transformed into a photocalorimeter. A general discussion of the basic principles of photocalorimetry, which we closely follow in the ensuing discussion, was made by Teixeira and Wadsö [179]. An amount of radiant energy E is supplied to the calorimetric cell and absorbed by the reaction mixture, initiating a chemical reaction.
Differential Scanning Calorimetry (DSC)
Authors: Martinho Simões José A. , da Piedade Manuel Minas
Published: November 2020

Physical and chemical changes may often be induced by raising or lowering the temperature of a substance. Typical examples are phase transitions, such as fusion, or chemical reactions, such as the solid state polymerization of sodium chloroacetate, which has an onset at 471 K: ClCH2COONa (cr) ⇋ NaCl (cr) + 1/n − (CH2COO)n − (pol) Differential scanning calorimetry (DSC) was designed to obtain the enthalpy or the internal energy of those processes and also to measure temperature-dependent properties of substances, such as the heat capacity. This is done by monitoring the change of the difference between the heat flow rate or power to a sample (S) and to a reference material (R), ΔΦ = ΦS − ΦR = (dQ/dt)S − (dQ/dt)R, as a function of time or temperature, while both S and R are subjected to a controlled temperature program. The temperature is usually increased or decreased linearly at a predetermined rate, but the apparatus can also be used isothermally. In some cases DSC experiments may provide kinetic data. According to Wunderlich, differential scanning calorimeters evolved from the differential thermal analysis (DTA) instruments built by Kurnakov at the beginning of the twentieth century. In these early DTA apparatus, the temperature difference between a sample and a reference, simultaneously heated by a single heat source, was measured as a function of time. No calorimetric data could be derived, and the instruments were used, for example, to determine the temperatures of phase transitions and to identify metals, oxides, minerals, soils, and foods. The attempts to obtain calorimetric data from DTA instruments eventually led to the development of DSC. The term differential scanning calorimetry and the acronym DSC were coined in 1963 when the first commercial instrument of this type became available. This apparatus was easy to operate, enabled fast experiments, and required only small samples (typically 5–10 mg). Its importance for materials characterization was immediately demonstrated and the DSC technique soon experienced a boom. New user-friendly commercial instruments were developed, and new applications were explored. It is, however, somewhat ironic that the method ows its still growing popularity to analytical rather than calorimetric uses.
Plants
Authors: Cody Martin L.
Published: November 2020

This chapter deals with the general features of plant diversity and distribution on the Sea of Cortés islands and to a lesser extent with adaptive features of plants such as morphology and phenology. This review is based mainly on the plant lists in appendixes 4.1-4.5 describing the island floras, endemics, and relicts. In our interpretations of these lists we draw from various floristic, systematic, and distributional works that pertain to the Gulf of California region and beyond. After an introductory section, we work from broader biogeographical questions to matters that have more local, specific, or taxonomically restricted perspectives. There must be few experiences in the biologist’s world to compare with approaching a “new” island by boat. The ingredients are adventure and suspense, mystery and perhaps even a little danger. There are feelings of discoveries to be made, knowledge to be extended, curiosity to be both piqued and satisfied. Such feelings are shared not only among natural historians but by any adventurous and curious traveler; the more difficult the island is to reach, the keener the excitement of the visit. The islands in the Sea of Cortés would seem ideally qualified to generate this sort of bioadventurism. They are mostly uninhabited and have been little explored biologically, and the mounting of small-scale expeditions to successfully reach (and leave) the islands is not always a trivial matter. First appearing as blurry, near-colorless breaks between the unrelenting blue of gulf and sky, the islands leave early impressions of abrupt topography and a seeming lack of vegetation. The dull-green smudge of plant life on foothill outwash fans and in the arroyos eventually becomes apparent, but almost up to the point of a landing the islands preserve the impression of rock masses broken only occasionally by bajadas on which a few cardons (Pachycereus pringlei) are conspicuous. Islands larger than a few square kilometers have well-developed drainage courses that reach the coasts as dry arroyos and provide breaks in the generally steep coastal cliffs. The beaches where the larger arroyos reach the coast are logical landing points, and here the visitor gets the first close look at the vegetation.
The Nonavian Reptiles : Origins and Evolution
Authors: Murphy Robert W. , Aguirre-Léon Gustavo
Published: November 2020

Early in the history of systematic biology, scientists were interested in documenting the wonders of “the creation.” Specimens procured on expeditions were placed in collections, and spectacular hand-colored plates graced giant monographs, showpieces of discovery and exploration. Darwin’s work shifted interests to natural selection and the process of speciation. In addition to Darwin’s volumes on evolution, whose main tenets were predicated on observations of island speciation patterns, Alfred Wallace’s (1880) Island Life explained the great diversity of species on islands. Today, in an expanded concept islands remains the central focus for investigations of speciation and the mechanisms that drive change. Islands come in the form of Petri dish cultures of bacteria, bottles of Drosophila, mesic sky islands (mountaintop habitats isolated by intervening desert), and subaerial landmasses (surrounded by water). Evolution has remained the unifying principle of biology, and the concepts and methods associated with it have made their way into virtually all aspects of human culture. Several groups of islands have been instructional in the development of evolutionary theory. The Galapagos Islands clearly had the greatest impact. However, the islands in the Sea of Cortés have also significantly influenced our understanding of the speciation process. Within herpetology, studies have looked at the evolution of insular gigantism (Case 1978b; Petren and Case 1997), anatomical and genetic variability (Soulé et al. 1973), and species composition (Case 1975, 1983; Murphy 1983a). Others have addressed island biogeography in the manner of MacArthur and Wilson’s (1963, 1967) model of colonization and extinction (Case 1975, 1983; Wilcox 1978, 1980) versus historical constraints imposed by plate tectonics (Murphy 1983). Various ecological attributes of insular populations have been compared to those of the founding source (reviewed in Case 1983). Controversies over peninsular effects have been evaluated (Taylor and Regal 1978, 1980; Seib 1980; Murphy 1991), as have the phylogenetic relationships of taxa (reviewed below). These are but a few examples of the herpetological investigations. The intensity of study in the Sea of Cortés has not waned in recent years. To the contrary, it has intensified. Renewed interest in the evolution of the Baja California herpetofauna owes much to the nature of the peninsula and its associated islands.
Paleolimnology at the Regional to Global Scale: Records of Climate Change
Authors: Cohen Andrew S.
Published: November 2020

Reconstructing climatic change is perhaps the single most common application of paleolimnology. Paleoclimatology is a vast subject, and several entire books have been written on this subject alone (e.g., Crowley and North, 1991; Parrish, 1998; Bradley, 1999). Here we can only touch on some of the more important, interesting, and controversial aspects of climate history that are potentially recorded in lake sediments. As with human impact histories, archives of paleoclimate from individual lakes record responses from both local and regional events (e.g., Giraudi, 1998); teasing the two apart from a single basin often poses a difficult problem. In order to differentiate regional from global-scale changes in climate from lake deposits, it is also necessary that local influences on hydrology, such as drainage diversions, or changes in groundwater flow fields unrelated to climate, be understood. The problem of identifying regionally significant events becomes even more acute when the goals are to assess the rate at which climate changed from lake records or to assess the synchroneity of events between locations. All of these issues accentuate the importance of excellent geochronometry for paleoclimatic interpretation. Also, biological or physical mixing of sediments in any individual core record may mislead us into thinking a change was gradual when in fact it was rapid, whereas unrecognized small-scale unconformities in a single core could mislead us in the opposite direction (Dominik et al., 1992). Conversely, some lakes act to amplify climatic signals, particularly when they cross a threshold of limnological response to some climate variable (for example the transition from closed to open-lake conditions that might accompany an increasing precipitation:evaporation ratio). In this case a ‘‘gradual’’ climatic process might appear rapid from its depositional record. As with human impact studies, a common solution to these problems is to use a comparative-lake and/or comparative-indicator approach, identifying coherent patterns of change in indicators of precipitation, temperature, windiness, or other climate variables of interest throughout a region. This can be done using many of the types of biotic, geochemical, geophysical, or geomorphic indicators we have discussed in chapters 7–11.
Paleolimnology in Deep Time: The Evolution of Lacustrine Ecosystems
Authors: Cohen Andrew S.
Published: November 2020

Most lakes are geologically ephemeral; even the longest-lived individual lakes persist only for tens of millions of years. However there is a continuity to lake systems that transcends the geologically short history of individual lake basins. This continuity comes from the long-term biological evolution of life in freshwater, and fittingly, forms the final subject of this treatment of paleolimnology. Like the oceans, lakes have provided habitats for living organisms for most of the earth’s history. Yet the patterns of aquatic ecosystem evolution in rivers and lakes have differed dramatically from those of the oceans. In large part this can be traced to the fundamentally ephemeral nature of most continental aquatic habitats and the ‘‘disconnectedness’’ in both time and space that exists between individual lakes and rivers compared with the world ocean. This pattern of temporal and spatial patchiness in water body distribution on the continents has shaped the evolution of lacustrine species and communities. Some understanding of this history can be gleaned from the study of modern ecology and molecular genetics of living freshwater organisms. But to understand long-term trends in lacustrine biodiversity and their relationship to the history of the lacustrine environment we must turn to the pre- Quaternary fossil record. Understanding this history, the timing and tempo of major species diversification and extinction events, and the evolution of key ecological innovations is critical for correctly interpreting ancient lake deposits. The fossil record of pre-Quaternary lakes is more difficult to interpret than that of more recent lake basins. Robust phylogenies are largely unavailable for clades of ancient lacustrine fossils, hindering our ability to test hypotheses of evolutionary ecology, although that situation hopefully will improve in coming years. Many major clades of fossil lacustrine organisms are extinct, and ecologies must be inferred from their depositional context. Even for organisms that have close-living relatives, our certainty in making inferences about habitat and relationship with other species weakens as we go back in time. Also the record we have to work with deteriorates with age, the result of (a) a declining volume of lake beds available for study with increasing age, (b) difficulties associated with processing lithified lake beds for their fossil content, and (c) an increasing likelihood of destruction by diagenesis with increasing age.