Showing papers in "The Quarterly Review of Biology in 1990"

The ecology and evolution of inducible defenses

Abstract: Inducible defenses are responses activated through a previous encounter with a consumer or competitor that confer some degree of resistance to subsequent attacks. While the importance of inducible resistance has long been known in host-parasite interactions, it is only recently that its importance has emerged in other natural systems. Althought the structural defenses produced by invertebrates to their competitors and predators are by no means the same as an immune response triggered by parasites, these responses all share the properties of (1) specificity, (2) amplification and (3) memory. This review discusses the following ecological consequences and evolutionary causes of inducible defenses: (1) Inducible defenses render historical factors important in biological interactions and can affect the probability of individual survival and growth, as well as affect population dynamics of consumers in some circumstances. (2) Although the benefits of inducible defenses are often balanced by fitness costs, incl...

Metabolic rate depression and biochemical adaptation in anaerobiosis, hibernation and estivation

Abstract: For many animals, the best defense against harsh environmental conditions is an escape to a hypometabolic or dormant state. Facultative metabolic rate depression is the common adaptive strategy of anaerobiosis, hibernation, and estivation, as well as a number of other arrested states. By reducing metabolic rate by a factor ranging from 5 to 100 fold or more, animals gain a comparable extension of survival time that can support months or even years of dormancy. The present review focuses on the molecular control mechanisms that regulate and coordinate cellular metabolism for the transition into dormancy. These include reversible control over the activity state of enzymes via protein phosphorylation or dephosphorylation reactions, pathway regulation via the association or dissociation of particle-bound enzyme complexes, and fructose-2,6-bisphosphate regulation of the use of carbohydrate reserves for biosynthetic purposes. These mechanisms, their interactions, and the regulatory signals (e.g., second messenger molecules, pH) that coordinate them form a common molecular basis for metabolic depression in anoxia-tolerant vertebrates (goldfish, turtles) and invertebrates (marine molluscs), hibernation in small mammals, and estivation in land snails and terrestrial toads.

Optimization, constraint, and history in the evolution of eyes.

Abstract: Several features of the evolution of eyes and photoreceptors are examined in an effort to explore the relative roles of adaptation and historical and developmental constraints. Optical design shows clear evidence of adaptation, which is some respects approaches optima predictable from physics. The primate fovea, on the other hand, illustrates how adaptation can be channeled by developmental heritage. The primary structure of opsins reveal multiple evolutionary lineages within both Drosophila and humans. The pigments of vertebrate rods comprise a subset of opsins whose evolutionary relationships map onto the phylogeny of the parent species. The evolutionary reasons for why most rod pigments absord maximally at 500 ± 10 nm are obscure, as there is no convincing explanation based on adaptation alone. Rods are appropriately distinguished from cones on the basis of which opsin gene is expressed. This criterion is likely to be in conflict with other difinitions in phyletic lines (e.g., geckos, snakes) that have...

Evolution in bacterial plasmids and levels of selection.

Abstract: Gene flow between different reproductive units such as bacterial plasmids and chromosomes presents unusual problems for evolutionary analysis. Far more than in eukaryotes, reproductive advantages at several levels of selection--genes, transposons, plasmids, cells, and clones--must be considered simultaneously to understand plasmid evolution. No level consistently prevails in conflict situations, and some reproductive units carry genes that restrain their own reproduction or survival, apparently to enhance the reproduction or survival of the higher-level reproductive units that carry them. Despite gene flow between plasmids and chromosomes, genes for certain functions show strong tendencies to occur on plasmids while others consistently occur on chromosomes. Functions generally associated with plasmids are diverse, but all are useful only in locally restricted contexts; it is argued that the selective consequences of the greater horizontal (within generation) transmission of plasmids are responsible for this pattern. The tendency for prokaryote transposons, which are also horizontally mobile, to carry genes similar to those commonly on plasmids supports this argument. The apparent trends in eukaryote plasmids and transposons to lack these same characters also accords with predictions of the local adaptation hypothesis, because genes on these genetic units are generally no more horizontally mobile than chromosomal genes. There are theoretical reasons to expect that plasmid genes tend to evolve more rapidly than chromosomal genes. "The selfish interests of genes have manifestly produced 'vehicles' in the forms of organelles, cells, individuals and yet higher units. If evolution is to predict as well as describe, then selfish interests must be understood in the framework of the constraints and opportunities generated by these 'vehicles'" (Buss, 1987, p. 182).

The evolution of seasonal delayed implantation.

Abstract: Seasonal delayed implantation has been described in 47 mammalian species in ten families, and has evolved independently at least 17 times. After reviewing earlier explanations for the phenomenon I present a hypothesis to explain the evolution of seasonal delay. I have assumed that females can increase their fitness by chossing their mates. Consequently, mating should take place during that time of year when the possibilities for female choice or male competition are greates. Time of birth is determined by ecological factors promoting survivals of the young, thereby setting certain constraints on the scheduling of the mating season. In certain situations, however, the possibilities for female choice or male competition can be increased by mating earlier; delay will increase female female fitness, and will thereby evolve. The hypothesis has been applied to all cases of seasonal delayed implantation.

The Structure and Confirmation of Evolutionary Theory.

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The Optimization Research Program: Studying Adaptations by Their Function

Abstract: We develop as a scientific research program (sensu Lakatos, 1978) the essential assumptions used in applying optimization techniques to the study of adaptation. The assumptions and hypotheses of the research program are of two kinds: (1) hard core and (2) strategic. Any prediction is derived from a conjuction of both hard-core and strategic hypothesis. The hard-core hypotheses define evolution as the change in the frequencies of strategies (rather than, for example, alleles or genotypes). Consequently, fitness is a property of strategies rather than genetic entities or individuals. Strategic hypotheses describe how a strategy's fitness depends on various inputs (e.g., mating success and energetic intake), and on how the feasible set of inputs to fitness is constrained. Strategies are described as being supervenient (sensu Rosenberg, 1985) on genotypes because while a given genotype specifies a strategy, a given strategy does not specify any finite set of genotypes. The supervenience of strategies lends cr...

Sex determination in Drosophila melanogaster.

Abstract: The understanding of sex determination is a fundamental goal in the study of eukaryotic developmental genetics. The mechanisms governing the generation of sexual dimorphism have been well characterized in Drosophila because of its amenability to both genetic manipulation and the application of the techniques of modern molecular genetics. By using classical genetics to search for sex-transforming mutations and by analysing their phenotypes and how they interact, a picture has emerged involving a cascade of regulatory genes. The primary sex determining signal--the ratio of the number of X chromosomes to the number of sets of autosomes--sets this cascade into motion. Genetic evidence has suggested that the intervening genes in this pathway are active in females but not in males, whereas the final gene has active but opposing roles in the two sexes. This bifunctional locus is responsible for the repression of female differentiation genes in males and male differentiation genes in females. The cloning of the key genes of the regulatory cascade and the study of their transcription patterns have revealed that their different functional states in the two sexes do not result from control at the transcriptional level, as might have been expected. Instead, common primary transcripts are produced in male and female flies; these are then differentially spliced to encode sex-specific gene products. In this paper we focus on the contributions of molecular genetics to the understanding of sex determination. Sufficient background is included for the reader to see how the models of the Drosophila sex determination system were first developed. We then show how the application of new technology has complemented the genetic approach and refined our understanding of the system. Current intensive research in this area should lead within the next few years to definitive knowledge at the molecular level of the cascade of differential splicing of regulatory genes, and how this hierarchy ultimately gives rise to the appropriate sex-specific patterns of structural gene expression that underlie sexual dimorphism.

Aquatic SciencesAntarctic Ocean and Resources Variability.Dietrich Sahrhage

Abstract: Announcing Continuous Article Publishing As of 2018, Aquatic Sciences has changed its publication structure from paginated issues to a consecutive publishing model: Continuous Article Publishing. This means that papers are published in a volume/issue immediately after acceptance. The Online First queue has become obsolete and the time from submission to publication in an issue is significantly shorter now. Continuous Article Publishing gives published articles full citation details instantly after online publication. As a further aspect of the new system, articles are no longer paginated sequentially by issue. Therefore, every article start swith page number 1. Page numbers are not used for article citation but every article has a citation ID number, called the ArticleCitationID. The ArticleCitationID is replacing the page numbers in the citation line, which includes the journal citation title, year, volume number and ArticleCitationID now. Example: Old: Aquat Sci (2017) 79:208-220 New: Aquat Sci (2018) 80: 123 This method of citation is accepted by the Web of Science/Journal Citation Reports (ISI). We feel that our authors and readers greatly benefit from this change in the publication structure of Aquatic Sciences.

The grim heritage of Lysenkoism: four personal accounts. V. In defense of Timoféeff-Ressovsky.

Abstract: T HE REPUTATION and integrity of the late great geneticist, N. W. Timof6effRessovsky [N. V. Timofeev-Resovsky, 19001981], have been recently attacked by certain German and Soviet scientists, writers, or journalists. These persons have attempted to incriminate him as a chief supporter of Nazi theories of race and genetic deterioration as well as a supporter of Nazi eugenic policies. In the West the most active accuser has been Benno Muller-Hill, a molecular geneticist who is a member of the Board of Directors of the Institute of Genetics, University of Cologne [K6ln], in West Germany. He has recently been joined by Karl Heinz Roth (1986), a physician and historian of Hamburg, who contributed to a book entitled Der Griff nach der Bevdlkerung an article entitled \"Schoner neuer Mensch,\" in which he traced the roots of Nazi eugenic policies to American and British investigators of genetic mutation and population genetics, but he especially singled out Timof6eff as the principal German scientific supporter of Nazi eugenic policies. His arguments have been severely criticized and rebutted by Bentley Glass, in a review of the book containing the article (Glass, 1989). In the Soviet Union, the attack upon Timof6eff-Ressovsky was launched by the journalists A. Kuzmin and V. Bondarenko, who are adherents or members of an ultranationalistic, racist society known as \"Memory.\" The writer Daniil Granin (1987), in his narrative Zubr [The Bison], while pretending to follow Gorbachev's new principle of \"openness\" [glasnost] and to call in question the unjust attitude of those in power toward Timofeeff during the regimes of Stalin, Khrushchev, and Brezhnev, actually managed to clear those political powers of guilt in the matter. He produced a highly distorted picture of Timof6eff. Even the title of his narrative is ambiguous, for the nearly extinct European bison (aurochs) means in colloquial Russian a person who stubbornly follows obsolete principles, a fossil. Like Khrushchev's minions, who swayed the destinies of prisoners, Granin would permit amnesty, but not rehabilitation, for TimofeeffRessovsky. Granin accused Timofeeff of staying in Germany when ordered to return to the USSR and of refusing to collect documents that would have proved his non-involvement either in framing the racist theory of the Nazis or in carrying out experimentation upon human beings who had been doomed to death. According to the opinion of Kuzmin and Bondarenko, it was Granin's duty to have unmasked Timofeeff's services to the Nazis, in order to prove that he did not deserve amnesty.

Principles of Nutritional Assessment.Rosalind S. Gibson

Abstract: Nutritional assessment systems have been undergoing revision over the last couple years. Among the common nutritional assessment methods include nutrition surveys, nutrition surveillance, nutrition screening, nutrition interventions and clinical assessments in clinical settings. Gibson has discussed in the book some of the new nutritional assessment techniques such as measurement of nutrients in dried blood spots prepared from a finger-prick blood sample. In addition, for some nutrients, on-site analysis is now possible, enabling researchers and subjects to obtain results immediately. The author equally reserved ample time for comprehensive and critical appraisal of many of the older, established methods in nutritional assessment like nutrition surveys.

The grim heritage of Lysenkoism: four personal accounts. IV. Difficult years in Soviet genetics.

Abstract: IN RECENT YEARS several publications have shed light on the difficult times in Soviet biology when T. D. Lysenko and his supporters were in power (Zh. Medvedev, The Rise and Fall of T D. Lysenko, Columbia Univ. Press, NewYork, 1969; TheMedvedevPapers. ThePlight of Soviet Science Today, Macmillan (St. Martin's Press), London, 1971; Soviet Science, Norton, New York, 1978; R. Berg, Acquired Traits. Memoirs of a Geneticist from the Soviet Union, Viking-Penguin, New York). These books have raised many questions, not only in the minds of the younger but also in those of the older generations in fact, among all who possess an interest in biology, yet were neither participants in, nor even witnesses to, the tumultuous events in biology during those difficult years. Even the most interested persons do not know to what disastrous consequences "Lysenkoism" led for the whole of biology, or what harm it did to the national economy. Even now, several decades later, it is worth answering such questions, after the antiscientific ideas of Lysenko and his supporters have been unmasked and their theories shown to be completely erroneous. It is, in fact, not only worth doing, but in my opinion it is necessary. Contemporary Soviet scientists, especially the younger ones, definitely need to learn the lesson, how important it is, always and everywhere, to stand for scientific truth, and to what fatal results the violation of ethical standards in science may lead. Such violations were typical of Lysenkos supporters, who used every means in their power to eliminate their scientific opponents in order to establish their own careers and to reach their personal goals. It is necessary to understand clearly how dangerous ignorance can be when it is in power. Beyond taking notice of all this, it is necessary to speak out about it, because even now Lysenkoism continues to exist, and no one should pretend that now all is well. All of these considerations, and more, have made me write down what I know about the lessons Lysenkoism has to teach us, even though it is not easy for me to remember all those difficult and bitter experiences endured by so many Soviet biologists (and I include myself), nor is it comfortable to recall the names of my dear teachers and coworkers who gave their lives for scientific truth. In the Soviet Union, the golden age of genetics began soon after the great October So-