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1.
Dobzhansky argued that biology only makes sense if life on earth has a shared history. But his dictum is often reinterpreted to mean that biology only makes sense in the light of adaptation. Some philosophers of science have argued in this spirit that all work in 'proximal' biosciences such as anatomy, physiology and molecular biology must be framed, at least implicitly, by the selection histories of the organisms under study. Others have denied this and have proposed non-evolutionary ways in which biologists can frame these investigations. This paper argues that an evolutionary perspective is indeed necessary, but that it must be a forward-looking perspective informed by a general understanding of the evolutionary process, not a backward-looking perspective informed by the specific evolutionary history of the species being studied. Interestingly, it turns out that there are aspects of proximal biology that even a creationist cannot study except in the light of a theory of their effect on future evolution.  相似文献   

2.
High-resolution analysis of activities of live cells is limited by the use of non-invasive methods. Apparatuses such as SEM, STM or AFM are not practicable because the necessary treatment or the harsh contact with system probe will disturb or destroy the cell. Optical methods are purely non-invasive, but they are usually diffraction limited and then their resolution is limited to approximately 1 microm. To overcome these restrictions, we introduce here the study of membrane activity of a live cell sample using a Scanning Near-field Optical Microscope (SNOM). A near field optical microscope is able to detect tiny vertical movement on the cell membrane in the range of only 1 nm or less, about 3 orders of magnitude better than conventional optical microscopes. It is a purely non-invasive, non-contact method, so the natural life activity of the sample is unperturbed. In this report, we demonstrated the nanometer-level resolving ability of our SNOM system analyzing cardiomyocytes samples of which membrane movement is known, and then we present new intriguing data of sharp 40 nm cell membrane sudden events on rat pheochromocytoma cell line PC12. All the measurements are carried out in culture medium with alive and unperturbed samples. We believe that this methodology will open a new approach to investigate live samples. The extreme sensitivity of SNOM allows measurements that are not possible with any other method on live biomaterial paving the way for a broad range of novel studies and applications.  相似文献   

3.
Philasterides dicentrarchi is an opportunistic histiophagous ciliate parasite causing systemic scuticociliatosis in cultured turbot (Scophthalmus maximus L.). This study investigated the effects of inoculation with live or killed trophozoites of this ciliate (plus 3% thioglycollate) on the in vitro phagocytic activity and respiratory-burst responses of inflammatory peritoneal leucocytes obtained from the fish thus treated. The phagocytic activity of leucocytes from fish inoculated with killed P. dicentrarchi was higher in the presence than in the absence of infected turbot serum (ITS). The effect of ITS was smaller in fish inoculated with live P. dicentrarchi, indicating modulation of the opsonic activity of ITS. Inoculation with live ciliates led to a significant increase in subsequent in vitro extracellular ROS production, but only when normal turbot serum (NTS) or ITS was included in the assay medium. Inclusion of live P. dicentrarchi in the medium abolished this increase, suggesting ROS-scavenging activity. Inoculation with live P. dicentrarchi led to a significant decline in subsequent in vitro intracellular ROS production; when NTS was included in the medium, there was a significant increase in intracellular ROS production, but no such increase was observed when ITS was included in the medium. Inoculation with live P. dicentrarchi alone did not increase subsequent in vitro NO? production in response to LPS; a significant increase was observed when NTS or ITS was included in the assay medium, but this increase was not affected by prior inoculation with P. dicentrarchi. These results suggest that the amphizoic nature of this parasite may reflect the ease with which it can develop mechanisms of evasion of the host immune response.  相似文献   

4.
Schloendorn J 《Bioethics》2006,20(4):191-202
In the close to medium future, the life sciences might permit a vast extension of the human life span. I will argue that this is a very desirable development for the individual person. The question whether death is a harm to the dying is irrelevant here. All it takes is that being alive is good for the living person and not being alive is not good for anyone. Thus, living persons who expect to live on happily are rationally required to want to stay alive. Eventual uncertainty whether it will be possible to be happy in the future provides no objection, but rather an incentive to try. This view, however, may be naive in assuming that persons are unchanging entities that exist separately from their psychological information. Objections have been derived from reductionistic views that value our future experiences in a way that declines with time, so that there will be a future point beyond which only negligible value accrues. If we adopt such a view, then we cannot now be concerned to have experiences beyond that point. I argue that these arguments fail to take into account all the reasons we might have to be concerned for the future and all kinds of such concern that come from them. The adoption of a plausible reductionistic account can arguably weaken our concern for the future and certainly change its quality in important ways. But this provides no objection to the desire to live forever, nor to live at all.  相似文献   

5.
Fieldwork is a branch of inseparable unity of natural and humanitarian sciences; it is aimed at the cultural origin of humanity on the maximum level of its variety. Practically all natural sciences have some space determined by ethnic conscience in nature cognition: ethnodemography, ethnobotany, ethnozoology, etc. Fieldwork guides the research of human culture from the laws of nature. This kind of knowledge is useful to balance human relations with nature and avoid conflicts. Peoples should exchange their wisdom in the dialogue with nature to be more safe. Fieldwork understood as traditional culture only, explaining the variety of ethnoses on our earth, is just the narrow and diachronic level of this branch of knowledge. The cosmological knowledge, where fantasy and not exhausted in its cognition understanding the world of nature are mixed, forms the source of fieldwork and in many respects explains the direction of knowledge: the man finds himself under the open sky, he is the child of nature. Then as time went on there appeared a gradual transition--first nature was creating the man, then by and by he began turning to answer nature by his activity. Nowadays the man is actively creating nature. There are two levels of fieldwork: the ancient one which deals with the origin of ethnoses and the modern one which explores how contemporary life is determined by ethnic specific traits. Fieldwork is the core of multidisciplinary situation in man's knowledge. It is related to such humanitarian sciences: semiotics, culturology, sociology, history, philosophy, literature, linguistics. In the cycle of natural sciences fieldwork stands close to anthropology, geography, biology, demography. Fieldwork as a science has the two main levels--the "sophy" level and the logos "level". The first one discovers wisdom of human life, the second one is aimed at logical structuring of knowledge, here proceed various classifications of peoples.  相似文献   

6.
A raster-based method for determining complex view factor patterns is presented (HURES model). The model uses Johnson and Watson’s view factor analysis method for fisheye lens photographs. The entire sphere is divided into 13 different view factors: open sky; sunny and shaded building walls, vegetation (trees) and ground surfaces above and below 1.2 m from the ground surface. The HURES model gave reasonable view factor results in tests at two urban study sites on summer days: downtown Nanaimo, B.C., Canada and Changwon, Republic of Korea. HURES gave better estimates of open sky view factors determined from fisheye lens photographs than did ENVI-met 3.1 and RayMan Pro. However, all three models underestimated sky view factor. For view factor analysis in outdoor urban areas, the 10° interval of rotation angle at 100 m distance of annuli will be suitable settings for three-dimensional computer simulations. The HURES model can be used for the rapid determination of complex view factor patterns which facilitates the analysis of their effects. Examples of how differing view factor patterns can affect human thermal sensation indices are given. The greater proportion of sunny view factors increased the computed predicted mean vote (PMV) by 1.3 on the sunny side of the street compared with the shady side during mid-morning in downtown Nanaimo. In another example, effects of differing amounts of open sky, sunny ground, sunny buildings and vegetation combined to produce only slight differences in PMV and two other human thermal sensation indices, PET and UTCI.  相似文献   

7.
Abstract The main aim of this paper is to present humanity and termites as design partners in the creation of a new dimension of ecosystem understanding. The paper by Turner and Soar, “Beyond biomimicry: What termites can tell us about realizing the living building” (2008) opens up a new era in how we think of human habitations, not only on earth, but perhaps on other planets, and using the termite model as the corner stone of innovative engineering. We know that termites are masters of constructing ‘buildings’ that meet all nutrition, energy, waste disposal needs, shelter, and food sources for many other animals and insects. We need to emulate the symbiotic abilities of termites to survive over time, for we all live on this symbiotic planet, and symbiosis is natural and common.  相似文献   

8.
The role of Ca2+ in the secretion of insulin and glucagon was investigated by studying the effects of Ca2+ ionophores on hormone secretion from isolated perifused islets of Langerhans. Ionophore X537A (100 muM), which binds alkaline earth cations and also complexes some univalent cations, caused a rapid transient increase in insulin and glucagon secretion which was not dependent on the presence of Ca2+ in the perifusion medium. Ionophore A23187 (100 muM), which specifically binds bivalent cations at neutral pH values, similarly increased insulin secretion in complete and Ca2+-free medium, but only stimulated glucagon release in the presence of extracellular Ca2+. Since the stimulatory effects of both ionophores were associated with an increased Ca2+ flux in the islets, these experiments support the hypothesis that Ca2+ may trigger the release of insulin and suggest that it is also involved in the secretion of glucagon. The basal rate of both insulin and glucagon release was significantly increased when Ca2+ was omitted from the perifusion medium, but it is proposed that this finding may be due to adverse effects on cell-membrane function under these conditions.  相似文献   

9.
Animals use a suite of sensory modalities to precisely locate and capture prey. While numerous studies have examined the effects of sensory deprivation on the behaviors leading to prey capture and while it is generally believed that information in the pre-strike period determines the way fish capture prey, this study is the first to examine the contribution of sensory information to jaw kinematics during capture. Largemouth bass were filmed using high-speed videography while capturing live mosquitofish. Bass were examined intact, with visual deprivation under infrared light, and with lateral line deprivation following treatment with cobalt chloride. Deprived of visual cues, this visual ram-feeding predator switches towards suction-based feeding to successfully capture prey. They approach prey slowly but open their mouths more rapidly, which has been shown to result in greater buccal pressure, causing their prey to move a greater distance at a more rapid velocity as they are being drawn into the predators' mouths. Deprived of lateral line cues, bass have higher forward velocities during capture and capture prey earlier in the gape cycle. This study demonstrates that sensory pre-strike information directly affects the capture modality employed by fishes and that fish can modulate between ram and suction not only by adjusting the amount of ram by increasing or decreasing their movements, but also by actively increasing the amount of suction used. These results suggest that the ability to modulate feeding behavior may allow animals to not only exploit a broader breadth of prey items, but also to be capable of doing so in a wider variety of environments.  相似文献   

10.
Euripides’ Alcestis (1959) raises the issue of ethical duties within families and exposes the romantic postures and rhetoric that can dominate such discussions. Should anybody be asked to sacrifice themselves or even undergo significant health risks for members of their own family? (An issue that is also relevant in considering our duties to future generations in terms of the earth we leave to them.) The issue that is dramatized to a heroic level in Alcestis arises in live organ and tissue donation within a family and challenges the idea that families should be trusted to sort out solutions that they can all live with. Alcestis intensifies the debate because the sacrifice of one life for another is its topic but, in doing so, it exposes many traps lying in wait for ethicists and medical jurists who boldly enter such debates (where emotions create shifting ground on which angels fear to tread).  相似文献   

11.
The location performance of a global positioning system (GPS) collar was assessed for different habitats and geographical areas. We tested the effects of habitat features, antenna position, movement, and fix interval on location performance around Mount Fuji, a single peak surrounded by wide and flat areas. Fix rate decreased from 100% in open flat areas to 53% under sloped dense canopy. The openness (the actual available sky, i.e., the percentage of a radio collar exposed to the sky when part of the collar is blocked due to terrain and vegetation) and canopy closure affected location accuracy and most other performance parameters. All nine habitat features except for available sky (theoretical, due to terrain) influenced location time. Any combination of obstructions between collar and satellite decreased the available number of satellites, the fix rate, increased the location time, and resulted in poorer location (higher DOP, lower 3-D proportion, or greater location error). A horizontal antenna yielded poorer location performance than a vertical one in the forest but not in the open area. Location performance always decreased when moving in forest rather than in open areas. Location performance changed with fix interval. Sixty-minute intervals resulted in a longer location time and a lower DOP than 10-min intervals. Vegetation affected location performance more than topography in the Mount Fuji area. Factors that cause a longer location time will shorten battery life. We suggest that location frequency and duration employed for field research should be decided by considering the aim of the study and the effects of habitat features, animal activity, and fix interval on GPS performance and battery longevity. The strengthened effect of canopy closure during windy weather should be considered for forest-dwelling animals.  相似文献   

12.
A seed has no flowers or leaves, and an egg no fingers or lungs. Yet plants and animals not only have these things but they resemble their parents in detail throughout their bodies. Something is inherited, but what is it? Life is based on the activities of cells. An organism has large numbers of them—a human has trillions! Cells live as separate units, which enables them each to do its own thing within its particular organ, but to be an organism they must work together. A cell can only detect its immediate local environment, but that includes various kinds of signals or information from nearby or far away within the body—or even from the external environment. It is by being local but responding globally in this way that an egg becomes an organism, an organism manages its way through life, and organisms make up species and ecosystems that interact with each other. The evolution of these abilities has produced the glorious array of living forms that populate the world. In these ways, an egg may have no thoughts but is a highly intelligent being.  相似文献   

13.
Homing ability of the cricket Gryllus campestriswas experimentally studied in the field after passive and active displacements. Whatever the weather conditions and the nature of the displacement, crickets (18/18) home directly when they are located between 5 and 15 cm from their burrow by performing real-time orientation. When moved by the experimenter between 15 and 55 cm away from home, some crickets (26/43) can retrieve their burrow by systematic searching only after winding inward trips but they get lost (0/18) beyond 55 cm. After self-generated movements between 5 and 85 cm away from home, crickets (33/35) return to their burrow under blue sky, but they cannot home as well under overcast sky (22/34 from 5 to 65 cm and 0/5 beyond). The volatile memory orientation system allowing path integration is based on the polarized skylight of the sun.  相似文献   

14.
In line with previous studies on organismic sets, the division of all organismic sets intogeneral autotrophic and heterotrophic is introduced. The first produce their food themselves from some external source of energy, which in general may be an energy of any kind. The others use other organismic sets as the source of their food and energy. On earth we know only one kind of generalgeneral autotrophic organismic sets, namely, the autotrophic plants which use solar radiation as their source of energy and for production of their own food. It is shown why autotrophic animals do not exist on earth except as microorganisms like, e.g.,Euglena. A rigorous proof of the previously derived theorem that in an organismic set of ordern>1 no element can be completely specialized is given. It requires the introduction of new postulates. Finally, in considering the organic world as a whole, the notion of organismic sets ofmixed order is introduced.  相似文献   

15.
The effects of a live yeast strain of Saccharomyces cerevisiae have been investigated on zoospore germination, metabolism, and cellulolytic activity of the anaerobic rumen fungus Neocallimastix frontalis MCH3. The addition of yeast cells to a vitamin-deficient medium stimulated the germination of fungal zoospores, increased cellulose degradation and hydrogen, formate, lactate, and acetate production. Responses depended on the concentration of yeast cells added and on their viability. Yeast supplementation provided vitamins such as thiamine, which is essential for fungal growth and activity. These results demonstrate that yeasts could enhance plant cell wall colonization by N. frontalis. With certain diets, yeasts could therefore be a good tool to optimize the microbial degradation of lignocellulosic materials, but more research is needed to understand their mechanisms of action, so that they can be used with maximum efficiency as feed supplements.  相似文献   

16.
As biodiversity hotspots, montane regions have been a focus of research to understand the divergence process. Like their oceanic counterparts, the diversity of the ‘sky islands’ might be ascribed to geographic isolation of mountaintops. However, because the sky islands, and especially those in northern latitudes, are subject to extreme climatic events such as the glacial cycles that drove both altitudinal and geographical shifts in species’ distributions, the dynamic colonization process is also a possible factor driving divergence. Here we test these two hypotheses (i.e. isolation versus colonization) in a flightless montane grasshopper, Melanoplus oregonensis, which is a member of a diverse group that radiated across the Rocky Mountains of North America. Using approximate Bayesian computation (ABC) and spatially explicit simulations that account for spatial heterogeneity and temporal shifts in species distributions, we show that a colonization model of the sky islands from refugial populations provides a significantly better fit to the empirical genetic data than a model of the geographic isolation among sky islands. Moreover, support for the colonization model holds irrespective of whether the movement of individuals was modeled as a diffusion process or was informed by differences in habitat suitabilities across the landscape. With validation analyses to confirm the models provide a good fit to the data, as well as general power and quality analyses, the research not only adds to a growing body of work on the complex dynamics underlying montane biodiversity, but it also provides much needed evaluation of competing hypotheses based on explicit models of the divergence process, as opposed to inferences about diversification drivers from species diversity patterns.  相似文献   

17.
The bark beetle Ips typographus carries numerous fungi that could be assisting the beetle in colonizing live Norway spruce (Picea abies) trees. Phenolic defenses in spruce phloem are degraded by the beetle's major tree-killing fungus Endoconidiophora polonica, but it is unknown if other beetle associates can also catabolize these compounds. We compared the ability of five fungi commonly associated with I. typographus to degrade phenolic compounds in Norway spruce phloem. Grosmannia penicillata and Grosmannia europhioides were able to degrade stilbenes and flavonoids faster than E. polonica and grow on minimal growth medium with spruce bark constituents as the only nutrients. Furthermore, beetles avoided medium amended with phenolics but marginally preferred medium colonized by fungi. Taken together our results show that different bark beetle-associated fungi have complementary roles in degrading host metabolites and thus might improve this insect's persistence in well defended host tissues.  相似文献   

18.
The live/dead fluorescent assay provides a quick method for assessing the proportion of live and dead cells in cell culture systems or tissues and is widely used. Dead cells are detected by the fluorescence produced when propidium iodide (PI) binds to DNA; PI and similar molecules are excluded from live cells but can penetrate dead cells because of their loss of membrane integrity. Here we investigated the effect of serum in the culture medium on the reliability of the method. We assessed viability of chondrocytes with/without serum using both a live/dead assay kit and also trypan blue staining. We found that after 2 days of culture, the DNA-binding dye PI could no longer detect dead cells if serum was present but they were readily detected in serum-free medium or if an inhibitor to DNase I was added to the serum-containing medium. Dead cells could be detected by trypan blue staining in all cultures. Hence dead cells are no longer detected as the DNase I present in serum degrades their DNA. DNA-binding dyes may thus not give a reliable estimate of the number of dead cells in systems that have been cultured in the presence of serum for several days.  相似文献   

19.
20.
Several species of columnar cacti in the Sonoran Desert contain isoquinoline alkaloids that are toxic to all but the resident drosophilids that feed and breed in necrotic stems. Cytochrome P450 enzymes are known to be involved in the metabolic detoxification of these alkaloids by the desert Drosophila and are consequently responsible for their ability to utilize these substrates. D. melanogaster is not normally exposed to these xenobiotic compounds and cannot live in necrotic cactus tissue. However, a previous study found evidence of a phenobarbital-inducible P450 in adults of this species that is capable of metabolizing cactus alkaloids. The current investigation sought to determine whether D. melanogaster responds to selection for alkaloid resistance. Significant increases in larval viability and adult longevity as well as shorter larvae-to-adult development times were observed after 16 generations of selection on medium containing isoquinoline alkaloids. The selected lines that exhibited a positive response can now be used to assay for changes in gene regulation as a possible mechanism of their response. This information will contribute to the understanding of evolution of P450-mediated resistance in insects.  相似文献   

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