Darwin's champions fight back.
Researchers are building their response to the attack by creationism on evolution as interest in Darwin memorabilia continues to grow.
Biological Evolution↗
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Results for “Continuous Evolution”
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Evolution operator for a multilevel system in a continuous-wave laser field.
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Journal Article↗
[Evolution of the blood levels of propofol administered by continuous perfusion during extracorporeal circulation].
The pharmacokinetics of propofol administered in continuous infusion was studied in 10 patients without left ventricular insufficiency during extracorporeal circulation (ECC) with hemodilution, for aortocoronary bypass. After a dosage of 1.5 mg.kg-1 during anaesthetic induction, the blood level was 4,800 micrograms.l-1. Under continuous infusion levels remained very high: they decreased by 40% during EEC induction and rose more than 10% when artificial ventilation started again. These modifications can be explained by physiological variations induced by EEC (non pulsated flow, redistribution, vasoconstriction, hemodilution, hypothermia) and they lead to adapt dosages in this type of anaesthesia.
Aged↗
The elective evolution.
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Continuity of Patient Care↗
[Evolution during sleep of a case of Kojewnikoff's continuous partial epilepsy].
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Aged↗
Sociobiology: the debate continues.
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Behavior↗
Four hundred-million-year-old vesicular arbuscular mycorrhizae.
The discovery of arbuscules in Aglaophyton major, an Early Devonian land plant, provides unequivocal evidence that mycorrhizae were established >400 million years ago. Nonseptate hyphac and arbuscules occur in a specialized meristematic region of the cortex that continually provided new cells for fungal infection. Arbuscules are morphologically identical to those of living arbuscular mycorrhizae in consisting of a basal trunk and repeatedly branched bush-like tuft within the plant cell. Although interpretations of the evolution of mycorrhizal mutualisms continue to be speculative, the existence of arbuscules in the Early Devonian indicates that nutrient transfer mutualism may have been in existence when plants invaded the land.
Journal Article↗
Evolution of polypyrimidines in Drosophila.
We surveyed 101 different Drosophila species for the presence of a particular highly repetitive DNA sequence containing long tracts of polypyrimidine/polypurine DNA, first found in D. melanogaster. Out of 55 tested species in the melanogaster group, only the sibling species D. simulans and D. mauritiana, as well as one distant relative in the ananassae subgroup, D. varians, contained the same sequence. All four of these species have long pyrimidine tracts as shown by acid hydrolysis of labelled DNA. All four species have the same sequence, bu the amount of this polypyrimidine/polypurine DNA varies greatly. Four other species in the hydei subgroup were found to contain a polypyrimidine/polpurine sequence, with an oligonucleotide composition different from that of D. melanogaster. This polypyrimidine DNA varies from as much as 10% of the total DNA in D. nigrohydei, to as little as 0.4% in D. neohydei. The long pyrimidine tracts in the hydei subgroup are often more than a thousand nucleotides in length, representing exceedingly homogeneous repetitious sequences.--These results show a rapid but discontinuous pattern of evolution for polypyrimidine/polypurine DNA . These sequences are not species specific, yet closely related species have greatly different amounts of polypyrimidines. Drastic changes occur in the amounts of these satellite type DNA sequences, as if the sequence had no continuous selective advantage in evolution. The implications of these results with regard to the general function and evolution of satellite DNA are discussed.
Animals↗
Large future genetic diversity losses are predicted even with habitat protection.
Genetic diversity within species is the basis for evolutionary adaptive capacity and has recently been included as a target for protection in the United Nations' Global Biodiversity Framework (GBF). However, we lack large-scale mathematical frameworks to quantify how much genetic diversity has already been lost, let alone to predict future losses under 21st century conservation scenarios. To fill this gap, we developed an area-based spatio-temporal predictive framework of genetic diversity calibrated with population-scale genomic data of 29 plant and animal species. To estimate present genetic diversity loss with our framework, we used species' habitat area and population sizes losses reported in the Living Planet Index, the Red List, and new GBF indicators across 13,808 species for the last 5 decades. Applying our evolutionary framework across these species, we estimate genetic diversity loss lags behind population and habitat area declines, with an estimated current 13-22% π genetic diversity loss. However, we forecast future genetic diversity losses will reach 41-76% even if populations are not further contracted. These results highlight that safeguarding existing habitats is insufficient to maintain the genetic health of species and relying solely on continuous genetic monitoring underestimates lagging long term impacts.
Genetic diversity↗
Continuous irradiation and flash-photolysis studies of new[3H]naphtho[2,1-b]pyrans linked by covalent bonds to oligothiophene units. Effect of thiophene substituents on the photochromism.
The influence of oligothiophene substituents on five new [3H]naphtho[2,1-b]pyrans has been investigated using flash photolysis and continuous irradiation techniques. Photochromic properties strongly depend on the number and position of the thienyl units. Thienyl substitution increases the UV/visible absorbance of the lower energy transition of both the naphthopyran and merocyanine isomers. The rate constants of the thermal fading processes also increase with the number of thiophenic entities. Although several minor photoisomers, whose relative amounts depend on the irradiation conditions could be involved, it has been assumed that under continuous monochromatic irradiation, the evolution of the photochromic reaction can be described by the formation of only one photoisomer. Under these conditions, quantum yields of photocolouration and molar absorption coefficients of the non-isolable photomerocyanine isomer were evaluated by photokinetic analysis. Flash-photolytic colourability can be interpreted using continuous irradiation parameters. A linear correlation has been established between experimental and calculated colourability. This result shows that similar photochromic reactions leading to similar photoisomers are triggered either by polychromatic flash photolysis or by continuous monochromatic irradiation.
Journal Article↗
Seeing double: gene duplication and diversification in plant secondary metabolism.
Gene duplications drive the recruitment of genes for secondary metabolism. Gene copies are gradually modified to create genes with specificities and expression patterns adapted to the needs of the new pathway in which they are involved. Duplicated genes are often in tandem repeats, forming clusters within the plant genome. However, in some cases, clusters of nonhomologous genes have also been identified as forming a functional unit. The selective forces that have caused the establishment of new pathways are far from understood and might have changed repeatedly during evolution owing to the continuously changing environment. Recent data show that the way several classes of secondary compounds are scattered among species is attributable to independent recruitment and the inactivation of biosynthetic enzymes.
Evolution, Molecular↗
Concerted evolution led to high expression of a prosimian primate delta globin gene locus.
The delta globin gene in simian primates is either weakly expressed (in hominoids and New World monkeys) or silent (in Old World monkeys). In prosimian primates, however, an unequal homologous crossover between the psi eta and delta loci of lemurs produced a hybrid psi eta delta pseudogene locus, whereas in tarsier the delta locus encodes a beta-type chain found in 18% of adult tarsier hemoglobin molecules. In the present study, the nucleotide and amino acid sequences of the galago delta and beta globin genes and their encoded peptides were determined, and evidence is provided showing that the galago delta locus encodes a beta-type chain (beta 2) found in 40% of the galago fetal and postnatal hemoglobin molecules, whereas the beta locus encodes the remaining 60% of the beta-type chain (beta 1). Galago beta 1 and beta 2 chains differ from each other by only one amino acid residue. The homology between the galago delta and beta loci extends from 800 base pairs 5' of the proximal CCAAT element to near the end of exon 3 as a result of a recombination event in which beta sequence replaced delta sequence. After this initial recombination event, concerted evolution between the loci continued over their conserved coding, intron 1, and promoter regions but failed to occur between the two loci in their intron 2 and distal 5'-flanking sequences where the two loci have now diverged by 20%. Calculations based on this divergence value and on a rate of noncoding sequence evolution of 4.2 x 10(-9) to 5.5 x 10(-9) substitutions/site/year for the lorisiform lineage to galago yielded a date of 18-24 million years ago for the initial recombination event. The fact that the promoter sequences of the galago delta locus are the same as that of the galago beta locus may account for the high level of expression of the galago delta gene.
Amino Acid Sequence↗
Evolution of organellar genomes.
Accumulating molecular data, particularly complete organellar genome sequences, continue to advance our understanding of the evolution of mitochondrial and chloroplast DNAs. Although the notion of a single primary origin for each organelle has been reinforced, new models have been proposed that tie the acquisition of mitochondria more closely to the origin of the eukaryotic cell per se than is implied by classic endosymbiont theory. The form and content of the ancestral proto-mitochondrial and proto-chloroplast genomes are becoming clearer but unusual patterns of organellar genome structure and organization continue to be discovered. The 'single-gene circle' arrangement recently reported for dinoflagellate chloroplast genomes is a notable example of a highly derived organellar genome.
Animals↗
Molecular genetics of speciation and human origins.
The major histocompatibility complex (MHC) plays a cardinal role in the defense of vertebrates against parasites and other pathogens. In some genes there are extensive and ancient polymorphisms that have passed from ancestral to descendant species and are shared among contemporary species. The polymorphism at the DRB1 locus, represented by 58 known alleles in humans, has existed for at least 30 million years and is shared by humans, apes, and other primates. The coalescence theory of populations genetics leads to the conclusion that the DRB1 polymorphism requires that the population ancestral to modern humans has maintained a mean effective size of 100,000 individuals over the 30-million-year persistence of this polymorphism. We explore the possibility of occasional population bottlenecks and conclude that the ancestral population could not have at any time consisted of fewer than several thousand individuals. The MHC polymorphisms exclude the theory claiming, on the basis of mitochondrial DNA polymorphisms, that a constriction down to one or few women occurred in Africa, at the transition from archaic to anatomically modern humans, some 200,000 years ago. The data are consistent with, but do not provide specific support for, the claim that human populations throughout the World were at that time replaced by populations migrating from Africa. The MHC and other molecular polymorphisms are consistent with a "multiregional" theory of Pleistocene human evolution that proposes regional continuity of human populations since the time of migrations of Homo erectus to the present, with distinctive regional selective pressures and occasional migrations between populations.
Animals↗
An in situ study of photosynthetic oxygen exchange and electron transport rate in the marine macroalga Ulva lactuca (Chlorophyta).
Direct comparisons between photosynthetic O(2) evolution rate and electron transport rate (ETR) were made in situ over 24 h using the benthic macroalga Ulva lactuca (Chlorophyta), growing and measured at a depth of 1.8 m, where the midday irradiance rose to 400-600 mumol photons m(-2) s(-1). O(2) exchange was measured with a 5-chamber data-logging apparatus and ETR with a submersible pulse amplitude modulated (PAM) fluorometer (Diving-PAM). Steady-state quantum yield ((F(m)'-F(t))/F(m)') decreased from 0.7 during the morning to 0.45 at midday, followed by some recovery in the late afternoon. At low to medium irradiances (0-300 mumol photons m(-2) s(-1)), there was a significant correlation between O(2) evolution and ETR, but at higher irradiances, ETR continued to increase steadily, while O(2) evolution tended towards an asymptote. However at high irradiance levels (600-1200 mumol photons m(-2) s(-1)) ETR was significantly lowered. Two methods of measuring ETR, based on either diel ambient light levels and fluorescence yields or rapid light curves, gave similar results at low to moderate irradiance levels. Nutrient enrichment (increases in [NO(3) (-)], [NH(4) (+)] and [HPO(4) (2-)] of 5- to 15-fold over ambient concentrations) resulted in an increase, within hours, in photosynthetic rates measured by both ETR and O(2) evolution techniques. At low irradiances, approximately 6.5 to 8.2 electrons passed through PS II during the evolution of one molecule of O(2), i.e., up to twice the theoretical minimum number of four. However, in nutrient-enriched treatments this ratio dropped to 5.1. The results indicate that PAM fluorescence can be used as a good indication of the photosynthetic rate only at low to medium irradiances.
Journal Article↗
The best defence against bioweapons has already been invented by evolution.
Bioweapons are considered from the viewpoint of the mutual evolution of microbe/victim ecological systems. Cases considered include accidental, experimental, and real exploitation of bioweapons as well as other cases in the history of epidemics, and also experimental investigations. It is proposed here that speculations about bioweapon's very high mass annihilating ability are based on over-extrapolation from limited data selected from the ancient history of epidemics and on a false supposition that all people are susceptible to any bioweapon's infectious agent. The history of epidemics, clinical and genetic observations, data from experimental investigations, and results of accidental, experimental, and real exploitation of bioweapons do not confirm the mass annihilating capability of bioweapons. Many people possess constitutional (genetic) immunity presumably formed by natural selection over many human generations. This genetic protection exists in an individual prior to infection. The power of constitutional immunity played an important role during all human evolution. Its protective capability continues to defend humanity from mass annihilation by both epidemics and bioweapons. In this context of constitutional immunity for the majority of individuals, the main goal of modern medicine is to identify and defend the defenseless ones.
Biodiversity↗
Evolutionary origins of depression: a review and reformulation.
There has been a recent surge of interest in the evolutionary basis of depression. One approach argues that the affective mechanisms that are dysregulated in depression are adaptations, whilst a second approach argues that depression itself is an adaptation. The evidence relating to whether depression could itself be an adaptation is reviewed. Adaptations generally have four hallmarks; they lack heritable variation, show evidence of good design, are evoked by appropriate triggers, and fitness is reduced where they are absent. Depression shows none of these hallmarks. It is characterized by heritability, recurrence, cognitive impairment, and poor social outcome. In an alternative evolutionary formulation, I argue that evolution has produced a continuous population distribution of affective reactivity that is subject to stabilizing selection. Individuals vulnerable to depression are at the upper end of this distribution. This conceptualization, in which depression itself is not selected for, is compatible with the known clinical and epidemiological facts.
Adaptation, Psychological↗
Synovial membrane cytokine profiles in reactive arthritis secondary to intravesical bacillus Calmette-Guérin therapy.
We describe the cellular infiltrate and cytokine profile in sequential synovial membrane biopsies from a patient with acute followed by chronic synovitis after intravesical bacillus Calmette-Guérin (BCG) therapy for an in situ transitional cell carcinoma of the bladder. Histological and immunohistochemical analysis of 3 synovial biopsies were done sequentially over a 9 month period. The patient was HLA-B27 positive, but HLA-DR4 negative, and did not have the "shared epitope." Unlike other cases, this patient's arthritis did not respond initially to nonsteroidal antiinflammatory drugs and was exacerbated by corticosteroid therapy. The synovitis took a neutrophilic form, with marked synovial membrane content of interleukin 8 (IL-8) and tumor necrosis factor alpha (TNF-alpha). It subsequently developed into chronic lymphoplasmacytoid synovitis, similar to rheumatoid arthritis (RA), with decreased IL-8 but continuing IL-1 and TNF-alpha production in the synovial membrane. The synovitis resolved to a fibrotic synovium with residual thickening of the synovial lining layer and continued production of TNF-alpha. Thus, during the evolution of this arthritis, the synovial layer and continued production of TNF-alpha. Thus, during the evolution of this arthritis, the synovial membrane yielded a cellular infiltrate and cytokine content that had marked similarities with that seen in RA; however, the arthritis eventually remitted spontaneously.
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