General Conclusions

2009 ◽  
Author(s):  
Thomas N. Sherratt ◽  
David M. Wilkinson
Keyword(s):  
Evolutionary Biology ◽  
Secondary Compounds ◽  
Evolutionary Origins ◽  
Casual Reader ◽  
Tropical Areas ◽  
Similar Vein ◽  
Almost All ◽  
The Tropics ◽  
Close Interrelationship ◽  
Evolutionary Explanations

Brett Dennen is a fine musician, but listening to his lyrics, one might be tempted to think that because we ‘do [or see] it every day’, then it does not deserve an explanation. Our book has dealt with a variety of everyday phenomena such as ageing, sex, species, a green world, and a blue sea, and we hope that by now our readers will agree that there is a reason why things are this way. Indeed, the fact that these phenomena are so commonplace makes the questions all the more important. The exciting thing is that while considerable progress has been made in each of the areas we address, we still do not have a complete answer to any of the questions we have posed. We use this short concluding chapter to pull together some common threads and to discuss some of the interrelationships between our answers. First and foremost, even the most casual reader will note that there is a close interrelationship between the ecological and evolutionary explanations we have presented. Taking the perspective of evolutionary biology, almost all of the evolutionary explanations we have proposed include an important ecological component. For example, ageing is now widely seen to arise as a consequence of there being relatively weak natural selection late in an organism’s life. Yet the primary reason for this ‘selective shadow’ is that predators and parasites are likely to have killed the organism long before it reaches an advanced stage of maturity. Likewise, one explanation for the evolution of sex is that the variation it generates allows at least some of the offspring to better compete with members of the same species, or to avoid parasitism. In a similar vein, many of the ecological phenomena we have sought to explain have evolutionary origins. For example, tropical areas may have more species because rates of speciation are greater in the tropics, or because rates of extinction are greater at high latitudes, or both. Likewise, plants have evolved secondary compounds to deter herbivory, and the presence of these compounds may go some way towards understanding why the world remains green.

scholarly journals Further twists in gastropod shell evolution

2008 ◽  
Vol 4 (2) ◽  
pp. 179-182 ◽  
Author(s):  
Reuben Clements ◽  
Thor-Seng Liew ◽  
Jaap Jan Vermeulen ◽  
Menno Schilthuizen
Keyword(s):  
Evolutionary Biology ◽  
Logarithmic Spiral ◽  
Spiral Growth ◽  
Evolutionary Perspective ◽  
Gastropod Shell ◽  
Form And Function ◽  
Evolutionary Origins ◽  
Taxonomic Groups ◽  
And Function ◽  
Shell Coiling

The manner in which a gastropod shell coils has long intrigued laypersons and scientists alike. In evolutionary biology, gastropod shells are among the best-studied palaeontological and neontological objects. A gastropod shell generally exhibits logarithmic spiral growth, right-handedness and coils tightly around a single axis. Atypical shell-coiling patterns (e.g. sinistroid growth, uncoiled whorls and multiple coiling axes), however, continue to be uncovered in nature. Here, we report another coiling strategy that is not only puzzling from an evolutionary perspective, but also hitherto unknown among shelled gastropods. The terrestrial gastropod Opisthostoma vermiculum sp. nov. generates a shell with: (i) four discernable coiling axes, (ii) body whorls that thrice detach and twice reattach to preceding whorls without any reference support, and (iii) detached whorls that coil around three secondary axes in addition to their primary teleoconch axis. As the coiling strategies of individuals were found to be generally consistent throughout, this species appears to possess an unorthodox but rigorously defined set of developmental instructions. Although the evolutionary origins of O. vermiculum and its shell's functional significance can be elucidated only once fossil intermediates and live individuals are found, its bewildering morphology suggests that we still lack an understanding of relationships between form and function in certain taxonomic groups.

Foliar habit in mistletoe–host associations

Botany ◽  
2017 ◽  
Vol 95 (3) ◽  
pp. 219-229 ◽  
Author(s):  
Gerhard Glatzel ◽  
Hanno Richter ◽  
Mohan Prasad Devkota ◽  
Guillermo Amico ◽  
Sugwang Lee ◽  
...  
Keyword(s):  
South America ◽  
Woody Plants ◽  
Wood Anatomy ◽  
Southern South America ◽  
Main Driver ◽  
Almost All ◽  
The Tropics ◽  
Nutrient Conservation ◽  
Large Vessels ◽  
Host Associations

Foliar habit in parasite–host associations of mistletoes and trees is a neglected aspect in the discussion of foliar habit of woody plants. Almost all of the world’s mistletoe species are evergreen, regardless of the foliar habit of their hosts. Deciduous mistletoes are rare and confined to the northern fringes of Loranthaceae in Eurasia, and to Misodendraceae and the monotypic genus Desmaria (Loranthaceae) in southern South America. There are no deciduous mistletoes in the tropics and subtropics. Based on existing information and hypotheses on foliar habit, we asked why the majority of mistletoe species is evergreen, even on deciduous hosts, and why seasonality is apparently no driver for the evolution of deciduousness in parasite–host systems. We postulate that nutrient conservation is the main driver for evergreenness in mistletoes. Based on our own observations of wood anatomy in the host–haustorium–mistletoe continuum we hypothesize that the phenomenon of deciduousness in northerly Loranthus species is a consequence of interrupted water supply in large vessels after frost. In South America we could not find a consistent correlation between wood anatomy and deciduousness. We assume that deciduousness in these mistletoes evolved long ago in Antarctic forests under climatic and ecological conditions quite different from today.

scholarly journals Disentangling Population History and Character Evolution among Hybridizing Lineages

2020 ◽  
Vol 37 (5) ◽  
pp. 1295-1305 ◽  
Author(s):  
Sean P Mullen ◽  
Nicholas W VanKuren ◽  
Wei Zhang ◽  
Sumitha Nallu ◽  
Evan B Kristiansen ◽  
...  
Keyword(s):  
Evolutionary Biology ◽  
De Novo ◽  
Balancing Selection ◽  
Incomplete Lineage Sorting ◽  
Introgressive Hybridization ◽  
Character Evolution ◽  
Population History ◽  
Lineage Sorting ◽  
Evolutionary Origins ◽  
Whole Genome Resequencing

Abstract Understanding the origin and maintenance of adaptive phenotypic novelty is a central goal of evolutionary biology. However, both hybridization and incomplete lineage sorting can lead to genealogical discordance between the regions of the genome underlying adaptive traits and the remainder of the genome, decoupling inferences about character evolution from population history. Here, to disentangle these effects, we investigated the evolutionary origins and maintenance of Batesian mimicry between North American admiral butterflies (Limenitis arthemis) and their chemically defended model (Battus philenor) using a combination of de novo genome sequencing, whole-genome resequencing, and statistical introgression mapping. Our results suggest that balancing selection, arising from geographic variation in the presence or absence of the unpalatable model, has maintained two deeply divergent color patterning haplotypes that have been repeatedly sieved among distinct mimetic and nonmimetic lineages of Limenitis via introgressive hybridization.

scholarly journals Glacier Fluctuations and Climate in the Cordillera Blanca, Peru

1990 ◽  
Vol 14 ◽  
pp. 136-140 ◽  
Author(s):  
Georg Kaser ◽  
Alcides Ames ◽  
Marino Zamora
Keyword(s):  
Seasonal Temperature ◽  
Wet Season ◽  
Equilibrium Line Altitude ◽  
Cordillera Blanca ◽  
Covered Area ◽  
Recession Rates ◽  
Tropical Areas ◽  
Precipitation Records ◽  
The Tropics

With a total of 723 km2 of glaciers (1970) the Cordillera Blanca includes the largest glacier-covered area in the tropics. The climate is characterized by relatively large daily and small seasonal temperature variations as well as by a distinct succession between a dry (May–September) and a wet season (October–April). Since the early 1970s an ablation stake network has been installed on the tongues of the glaciers Uruashraju and Yanamarey. The determination of the equilibrium-line altitude at each end of a wet season was possible, showing a fair correlation with temperature, but not with the precipitation records of the nearby climatological station Querococha. Mean ablation rates at the lowest parts of the glacier tongues are markedly higher during the wet season than during the dry season. Reasons are presumably to be found in the seasonal variation of cloudiness and air moisture rates. Terminus variations of four glaciers in the Cordillera Blanca have been monitored since the early seventies, earlier positions are reconstructed back to 1948 by vertical air photographs. For the glaciers Uruashraju and Yanamarey the terminus positions of 1939 are known from an early map. The general retreat of glaciers in the Cordillera Blanca during the last five decades correlates with the global attitude of glaciers and especially with the attitude of glaciers in other tropical areas. Decreased recession rates with minor advances (1974–79 and 1985–86) are accompanied by lower annual temperatures and preceded and accompanied by years with relatively high annual precipitation sums.

scholarly journals Polyamines in Microalgae: Something Borrowed, Something New

Marine Drugs ◽  
2018 ◽  
Vol 17 (1) ◽  
pp. 1 ◽  
Author(s):  
Hung-Yun Lin ◽  
Han-Jia Lin
Keyword(s):  
Amino Acids ◽  
Primary Production ◽  
Metabolic Pathways ◽  
Food Source ◽  
Biotechnological Applications ◽  
Evolutionary Origins ◽  
Microbial Ecosystems ◽  
Polyamine Content ◽  
Synthetic Routes ◽  
Almost All

Microalgae of different evolutionary origins are typically found in rivers, lakes, and oceans, providing more than 45% of global primary production. They provide not only a food source for animals, but also affect microbial ecosystems through symbioses with microorganisms or secretion of some metabolites. Derived from amino acids, polyamines are present in almost all types of organisms, where they play important roles in maintaining physiological functions or against stress. Microalgae can produce a variety of distinct polyamines, and the polyamine content is important to meet the physiological needs of microalgae and may also affect other species in the environment. In addition, some polyamines produced by microalgae have medical or nanotechnological applications. Previous studies on several types of microalgae have indicated that the putative polyamine metabolic pathways may be as complicated as the genomes of these organisms, which contain genes originating from plants, animals, and even bacteria. There are also several novel polyamine synthetic routes in microalgae. Understanding the nature of polyamines in microalgae will not only improve our knowledge of microalgal physiology and ecological function, but also provide valuable information for biotechnological applications.

Tropical diseases of importance to the traveller

1982 ◽  
Vol 82 (1-2) ◽  
pp. 57-60
Author(s):  
A. W. Woodruff
Keyword(s):  
Far East ◽  
Developed Countries ◽  
Lassa Fever ◽  
Special Importance ◽  
Helminthic Infections ◽  
Established Disease ◽  
Tropical Areas ◽  
The Tropics ◽  
Tropical Infections ◽  
Important Disease

SynopsisThe most important disease for the traveller to avoid and for physicians to suspect in travellers is malaria. All tropical Africa and most tropical areas in the East and Far East are now malarious. The infection has returned in recent years to India and several other parts of the East and Far East from which it had been almost eradicated. Travellers to those regions should, therefore, take appropriate malarial prophylactics and malaria should be the cause first suspected among those with fever who have recently visited malarious areas. The emergence of malarial strains resistant to chloroquine poses problems both for prophylaxis and treatment of the established disease.The recognition in 1969 of Lassa fever has introduced a new problem in managing those with fever who have been to West Africa within the preceding three weeks.Travellers to game parks in Africa have greatly increased in number within the last decade and are exposed to trypanosomiasis. Several cases resulting from such exposure are known. They cause special diagnostic problems.Hepatic amoebiasis may be unsuspected until a considerable amount of pus has collected and the risk of complications developed. Its clinical features need to be borne in mind.Helminthic infections are ubiquitous in the tropics. Schistosomiasis, ascariasis and strongyloidiasis are of special importance and practitioners in developed countries need to be familiar with their characteristics.Awareness of the possible presence of tropical infections is the keynote to success both in avoiding them and in managing them among those whose precautions have been deficient.

scholarly journals Solar geoengineering using solid aerosol in the stratosphere

2015 ◽  
Vol 15 (20) ◽  
pp. 11835-11859 ◽  
Author(s):  
D. K. Weisenstein ◽  
D. W. Keith ◽  
J. A. Dykema
Keyword(s):  
Radiative Forcing ◽  
Injection Rate ◽  
Sulfate Aerosols ◽  
Limited Data ◽  
Aerosol Model ◽  
Alumina Particles ◽  
Solar Geoengineering ◽  
Almost All ◽  
The Tropics ◽  
Solid Aerosol

Abstract. Solid aerosol particles have long been proposed as an alternative to sulfate aerosols for solar geoengineering. Any solid aerosol introduced into the stratosphere would be subject to coagulation with itself, producing fractal aggregates, and with the natural sulfate aerosol, producing liquid-coated solids. Solid aerosols that are coated with sulfate and/or have formed aggregates may have very different scattering properties and chemical behavior than uncoated non-aggregated monomers do. We use a two-dimensional (2-D) chemistry–transport–aerosol model to capture the dynamics of interacting solid and liquid aerosols in the stratosphere. As an example, we apply the model to the possible use of alumina and diamond particles for solar geoengineering. For 240 nm radius alumina particles, for example, an injection rate of 4 Tg yr−1 produces a global-average shortwave radiative forcing of −1.2 W m−2 and minimal self-coagulation of alumina although almost all alumina outside the tropics is coated with sulfate. For the same radiative forcing, these solid aerosols can produce less ozone loss, less stratospheric heating, and less forward scattering than sulfate aerosols do. Our results suggest that appropriately sized alumina, diamond or similar high-index particles may have less severe technology-specific risks than sulfate aerosols do. These results, particularly the ozone response, are subject to large uncertainties due to the limited data on the rate constants of reactions on the dry surfaces.

scholarly journals What have humans done for evolutionary biology? Contributions from genes to populations

2017 ◽  
Vol 284 (1866) ◽  
pp. 20171164 ◽  
Author(s):  
Michael Briga ◽  
Robert M. Griffin ◽  
Vérane Berger ◽  
Jenni E. Pettay ◽  
Virpi Lummaa
Keyword(s):  
Natural Selection ◽  
Evolutionary Biology ◽  
Human Study ◽  
Human Studies ◽  
Human Populations ◽  
Evolutionary Processes ◽  
Biological Relevance ◽  
Evolutionary Studies ◽  
Almost All ◽  
Study Designs

Many fundamental concepts in evolutionary biology were discovered using non-human study systems. Humans are poorly suited to key study designs used to advance this field, and are subject to cultural, technological, and medical influences often considered to restrict the pertinence of human studies to other species and general contexts. Whether studies using current and recent human populations provide insights that have broader biological relevance in evolutionary biology is, therefore, frequently questioned. We first surveyed researchers in evolutionary biology and related fields on their opinions regarding whether studies on contemporary humans can advance evolutionary biology. Almost all 442 participants agreed that humans still evolve, but fewer agreed that this occurs through natural selection. Most agreed that human studies made valuable contributions to evolutionary biology, although those less exposed to human studies expressed more negative views. With a series of examples, we discuss strengths and limitations of evolutionary studies on contemporary humans. These show that human studies provide fundamental insights into evolutionary processes, improve understanding of the biology of many other species, and will make valuable contributions to evolutionary biology in the future.

scholarly journals Evolution of the patellar sesamoid bone in mammals

2016 ◽  
Author(s):  
Mark E Samuels ◽  
Sophie Regnault ◽  
John R Hutchinson
Keyword(s):  
Knee Joint ◽  
Meta Analysis ◽  
Large Body ◽  
Extensor Tendon ◽  
Initial Step ◽  
Sesamoid Bone ◽  
Crown Group ◽  
Evolutionary Origins ◽  
Lever System ◽  
Almost All

The patella is a sesamoid bone located in the major extensor tendon of the knee joint, in the hindlimb of many tetrapods. Although numerous aspects of knee morphology are ancient and conserved among most tetrapods, the evolutionary occurrence of the patella is highly variable. Among extant (crown clade) groups it is found in most birds, most lizards, the monotreme mammals and almost all placental mammals, but it is absent in most marsupial mammals as well as many reptiles. Here we integrate data from the literature and first-hand studies of fossil and recent skeletal remains to reconstruct the evolution of the mammalian patella. We infer that patellae most likely evolved between four to six times in crown group Mammalia: in monotremes, in the extinct multituberculates, in one or more stem-mammal genera outside of therian or eutherian mammals, and up to three times in therian mammals. Furthermore, a patella was lost several times in mammals, not including those with absent hindlimbs: once or more in marsupials (with some re-acquisition), and at least once in bats. Our inferences about patellar evolution in mammals are reciprocally informed by the existence of several human genetic conditions in which the patella is either absent or severely reduced. Clearly, development of the patella is under close genomic control, although its responsiveness to its mechanical environment is also important (and perhaps variable among taxa). Where a patella is present it plays an important role in hindlimb function; especially in resisting gravity by providing an enhanced lever system for the knee joint. Yet the evolutionary origins, persistence and modifications of a patella in diverse groups with widely varying habits and habitats -- from digging to running to aquatic, small or large body sizes, bipeds or quadrupeds -- remain complex and perplexing, impeding a conclusive synthesis of form, function, development and genetics across mammalian evolution. This meta-analysis takes an initial step toward such a synthesis by collating available data and elucidating areas of promising future inquiry.

scholarly journals FORMULASI DAN UJI SIFAT FISIK MASKER ANTIJERAWAT DARI EKSTRAK SABUT KELAPA ( Cocos nucifera L)

2020 ◽  
Vol 2 (1) ◽  
pp. 42-51
Author(s):  
Fauziah Fauziah ◽  
Rima Marwarni ◽  
Azmalina Adriani
Keyword(s):  
Physical Properties ◽  
Cocos Nucifera ◽  
Face Mask ◽  
Drying Time ◽  
Coconut Coir ◽  
Cocos Nucifera L ◽  
Almost All ◽  
The Tropics ◽  
Very High ◽  
Active Substances

Coconut is a multipurpose tree for people in the tropics. Almost all parts can be used such as leaves, fruit, stems, and roots. Besides having many benefits of coconut, it also produces waste from its fruit, namely coconut fiber. Coconut coir has a very high tannin content. In general, tannin compounds can be indicated as anti-inflammatory, and anti-bacterial. The purpose of this study was to formulate the anti-acne mask from coconut coir extract and to test its physical properties. This study uses an experimental research method, in which three mask formulas are made with variations in the concentration of active substances and polyvinyl alcohol (PVA). In this study the active substance used was coconut coir extract. The formulas used are formulas A, B, and C with the concentration of active substances successively as follows: 1%, 2%, 4%. The results of research that have been carried out that the mask formula that has the best physical properties is formula B, because it fulfills the physical properties provisions of the peel off face mask including organoleptic, homogeneity, pH, dispersal power, and drying time.

Sign in / Sign up

Export Citation Format

Share Document