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1.
Evolution of the bilaterian germ line: lineage origin and modulation of specification mechanisms 总被引:2,自引:0,他引:2
Extavour CG 《Integrative and comparative biology》2007,47(5):770-785
A key focus of evolutionary developmental biology (evo–devo)in recent years has been to elucidate the evolution of developmentalmechanisms as a means of reconstructing the hypothetical lastcommon ancestors of various clades. Prominent among such reconstructionshave been proposals as to the nature of the mysterious "Urbilateria,"originally defined as the last common ancestor of the extantBilateria (protostomes and deuterostomes). Indeed, drawingsof this animal can now be found, as well as detailed informationon the genetics and morphological processes that it used toconstruct its gut, heart, eyes, appendages, segments, and bodyregions. Perhaps surprisingly, however, no explanations haveyet been offered as to how this animal might have achieved thesuccessful reproduction that must have been necessary for itto give rise to those lineages that are ancestral to today'sdiverse clades. The present article examines the comparativedata available to date on the specification of the only cellscontaining the genetic hereditary material, the germ cells,and speculates on the possible evolutionary and developmentalorigin of the Urbilaterian germ line. 相似文献
2.
A Closer Look at Amphetamine-Induced Reverse Transport and Trafficking of the Dopamine and Norepinephrine Transporters 总被引:1,自引:0,他引:1
Amphetamine (AMPH) and its derivatives are regularly used in the treatment of a wide array of disorders such as attention-deficit
hyperactivity disorder (ADHD), obesity, traumatic brain injury, and narcolepsy (Prog Neurobiol 75:406–433, 2005; J Am Med Assoc 105:2051–2054, 1935; J Am Acad Child Adolesc Psychiatry 41:514–521, 2002; Neuron 43:261–269, 2004; Annu Rev Pharmacol Toxicol 47:681–698, 2007; Drugs Aging 21:67–79, 2004). Despite the important medicinal role for AMPH, it is more widely known for its psychostimulant and addictive properties
as a drug of abuse. The primary molecular targets of AMPH are both the vesicular monoamine transporters (VMATs) and plasma
membrane monoamine—dopamine (DA), norepinephrine (NE), and serotonin (5-HT)—transporters. The rewarding and addicting properties
of AMPH rely on its ability to act as a substrate for these transporters and ultimately increase extracellular levels of monoamines.
AMPH achieves this elevation in extracellular levels of neurotransmitter by inducing synaptic vesicle depletion, which increases
intracellular monoamine levels, and also by promoting reverse transport (efflux) through plasma membrane monoamine transporters
(J Biol Chem 237:2311–2317, 1962; Med Exp Int J Exp Med 6:47–53, 1962; Neuron 19:1271–1283, 1997; J Physiol 144:314–336, 1958; J Neurosci 18:1979–1986, 1998; Science 237:1219–1223, 1987; J Neurosc 15:4102–4108, 1995). This review will focus on two important aspects of AMPH-induced regulation of the plasma membrane monoamine transporters—transporter
mediated monoamine efflux and transporter trafficking. 相似文献
3.
Jurgen F. Doreleijers Wim F. Vranken Christopher Schulte Jundong Lin Jonathan R. Wedell Christopher J. Penkett Geerten W. Vuister Gert Vriend John L. Markley Eldon L. Ulrich 《Journal of biomolecular NMR》2009,45(4):389-396
Several pilot experiments have indicated that improvements in older NMR structures can be expected by applying modern software
and new protocols (Nabuurs et al. in Proteins 55:483–186, 2004; Nederveen et al. in Proteins 59:662–672, 2005; Saccenti and Rosato in J Biomol NMR 40:251–261, 2008). A recent large scale X-ray study also has shown that modern software can significantly improve the quality of X-ray structures
that were deposited more than a few years ago (Joosten et al. in J. Appl Crystallogr 42:376–384, 2009; Sanderson in Nature 459:1038–1039, 2009). Recalculation of three-dimensional coordinates requires that the original experimental data are available and complete,
and are semantically and syntactically correct, or are at least correct enough to be reconstructed. For multiple reasons,
including a lack of standards, the heterogeneity of the experimental data and the many NMR experiment types, it has not been
practical to parse a large proportion of the originally deposited NMR experimental data files related to protein NMR structures.
This has made impractical the automatic recalculation, and thus improvement, of the three dimensional coordinates of these
structures. We here describe a large-scale international collaborative effort to make all deposited experimental NMR data
semantically and syntactically homogeneous, and thus useful for further research. A total of 4,014 out of 5,266 entries were
‘cleaned’ in this process. For 1,387 entries, human intervention was needed. Continuous efforts in automating the parsing
of both old, and newly deposited files is steadily decreasing this fraction. The cleaned data files are available from the
NMR restraints grid at . 相似文献
4.
Hyosig Won 《Journal of Plant Biology》2009,52(5):411-416
Recent phylogenetic research suggests that Malvaceae s.l. comprises formerly Tiliaceae, Byttneriaceae, Bombacaceae, and Sterculiaceae.
Corchoropsis is traditionally included in Tiliaceae or Sterculiaceae and is distributed in China, Korea, and Japan. One to three species
have been recognized for this genus. Phylogenetic relationships among the Malvacean taxa have been intensively studied with
molecular data, and the evolution of their morphological characteristics has been re-interpreted accordingly. However, no
Corchoropsis species have been included for their phylogenetic position. Here, three chloroplast coding regions—rbcL, atpB, and ndhF, from Corchoropsis psilocarpa and Corchoropsis crenata—were amplified and sequenced, then compared with other Malvacean taxa. This analysis of the three plastid gene sequences
now places Corchoropsis species in Dombeyoideae, as previously proposed by Takeda (Bull Misc Inform Kew 365, 1912), Tang (Cathaya 4:131–150, 1992), and Bayer and Kubitzki (2003). Within Dombeyoideae, Corchoropsis forms a strongly supported sister relationship with the Dombeya–Ruizia clade. 相似文献
5.
Prakash Mondal 《Biosemiotics》2012,5(1):61-82
This paper is an attempt at exploring the possibility of reconciling the two interpretations of biolinguistics which have
been recently projected by Koster (Biolinguistics 3(1):61–92, 2009). The two interpretations—trivial and nontrivial—can be roughly construed as non-internalist and internalist conceptions
of biolinguistics respectively. The internalist approach boils down to a conception of language where language as a mental
grammar in the form of I-language grows and functions like a biological organ. On the other hand, under such a construal consistent
with Koster’s (Biolinguistics 3(1):61-92, 2009), the non-internalist version does not necessarily have to be externalist in nature; rather it is a matter of mutual reinforcement
of biology and culture under the rubric of a co-evolutionary dynamics. Here it will be argued that the apparent dichotomy
between these two conceptions of biolinguistics can perhaps be resolved if we have a richer synthesis that accounts for both
internalism and non-internalism. 相似文献
6.
Acidithiobacillus thiooxidans secretome containing a newly described lipoprotein Licanantase enhances chalcopyrite bioleaching rate 总被引:1,自引:0,他引:1
The nature of the mineral–bacteria interphase where electron and mass transfer processes occur is a key element of the bioleaching
processes of sulfide minerals. This interphase is composed of proteins, metabolites, and other compounds embedded in extracellular
polymeric substances mainly consisting of sugars and lipids (Gehrke et al., Appl Environ Microbiol 64(7):2743–2747, 1998). On this respect, despite Acidithiobacilli—a ubiquitous bacterial genera in bioleaching processes (Rawlings, Microb Cell
Fact 4(1):13, 2005)—has long been recognized as secreting bacteria (Jones and Starkey, J Bacteriol 82:788–789, 1961; Schaeffer and Umbreit, J Bacteriol 85:492–493, 1963), few studies have been carried out in order to clarify the nature and the role of the secreted protein component: the secretome.
This work characterizes for the first time the sulfur (meta)secretome of Acidithiobacillus thiooxidans strain DSM 17318 in pure and mixed cultures with Acidithiobacillus ferrooxidans DSM 16786, identifying the major component of these secreted fractions as a single lipoprotein named here as Licanantase.
Bioleaching assays with the addition of Licanantase-enriched concentrated secretome fractions show that this newly found lipoprotein
as an active protein additive exerts an increasing effect on chalcopyrite bioleaching rate. 相似文献
7.
In plants, reactive oxygen species (ROS) are short-lived molecules produced through various cellular mechanisms in response
to biotic and abiotic stimuli. ROS function as second messengers for hormone signaling, development, oxygen deprivation, programmed
cell death, and plant–pathogen interactions. Recent research on ROS-mediated responses has produced stimulating findings such
as the specific sources of ROS production, molecular elements that work in ROS-mediated signaling and homeostasis, and a ROS-regulated
gene network (Neill et al., Curr Opin Plant Biol 5:388–395, 2002a; Apel and Hirt, Annu Rev Plant Biol 55:373–399, 2004; Mittler et al., Trends Plant Sci 9:490–498, 2004; Mori and Schroeder, Plant Physiol 135:702–708, 2004; Kwak et al., Plant Physiol 141:323–329, 2006; Torres et al., Plant Physiol 141:373–378, 2006; Miller et al., Physiol Plant 133:481–489, 2008). In this review, we highlight new discoveries in ROS-mediated abscisic acid (ABA) signaling.
Drs. Daeshik Cho and June M. Kwak are the corresponding authors for this paper. 相似文献
8.
Simulation of biological evolution under attack,but not really: a response to Meester 总被引:1,自引:0,他引:1
The leading Intelligent Design theorist William Dembski (Rowman & Littlefield, Lanham MD, 2002) argued that the first No Free Lunch theorem, first formulated by Wolpert and Macready (IEEE Trans Evol Comput 1: 67–82,
1997), renders Darwinian evolution impossible. In response, Dembski’s critics pointed out that the theorem is irrelevant to biological
evolution. Meester (Biol Phil 24: 461–472, 2009) agrees with this conclusion, but still thinks that the theorem does apply to simulations of evolutionary processes. According
to Meester, the theorem shows that simulations of Darwinian evolution, as these are typically set in advance by the programmer,
are teleological and therefore non-Darwinian. Therefore, Meester argues, they are useless in showing how complex adaptations
arise in the universe. Meester uses the term “teleological” inconsistently, however, and we argue that, no matter how we interpret
the term, a Darwinian algorithm does not become non-Darwinian by simulation. We show that the NFL theorem is entirely irrelevant
to this argument, and conclude that it does not pose a threat to the relevance of simulations of biological evolution. 相似文献
9.
Agarwal B 《Journal of bioenergetics and biomembranes》2011,43(3):299-310
ATP, the ‘universal biological energy currency’, is synthesized by utilizing energy either from oxidation of fuels or from
light, via the process of oxidative and photo-phosphorylation respectively. The process is mediated by the enzyme F1F0-ATP synthase, using the free energy of ion gradients in the final energy catalyzing step, i.e., the synthesis of ATP from
ADP and inorganic phosphate (Pi). The details of the molecular mechanism of ATP synthesis are among the most important fundamental issues in biology and
hence need to be properly understood. In this work, a role for anions in making ATP has been found. New experimental data
has been reported on the inhibition of ATP synthesis at nanomolar concentrations by the potent, specific anion channel blockers
4,4′-diisothiocyanostilbene-2, 2′-disulphonic acid (DIDS) and tributyltin chloride (TBTCl). Based on these inhibition studies,
attention has been drawn to anion translocation (in addition to proton translocation) as a requirement for ATP synthesis.
The type of inhibition has been quantified and an overall kinetic scheme for mixed inhibition that explains the data has been
evolved. The experimental data and the type of inhibition found have been interpreted in the light of the torsional mechanism
of energy transduction and ATP synthesis (Nath J Bioenerg Biomembr 42:293–300, 2010a; J Bioenerg Biomembr 42:301–309, 2010b). This detailed and unified mechanism resolves long-standing problems and inconsistencies in the first theories (Slater Nature
172:975–978, 1953; Williams J Theor Biol 1:1–17, 1961; Mitchell Nature 191:144–148, 1961; Mitchell Biol Rev 41:445–502, 1966), makes several novel predictions that are experimentally verifiable (Nath Biophys J 90:8–21, 2006a; Process Biochem 41:2218–2235, 2006b), and provides us with a new and fruitful paradigm in bioenergetics. The interpretation presented here provides intelligent
answers to the unexplained existing results in the literature. It is shown that mechanistic interpretation of the experimental
data requires substantial addition to available conceptual foundations such that present concepts, theories, and mechanisms
must be revised. 相似文献
10.
Annat Haber 《Evolutionary biology》2011,38(4):476-488
The degree of integration of multidimensional phenotypes has an important place in evolutionary biology, pertaining to the
structure of variation that is available for natural selection to work on and therefore to the evolutionary potential of the
phenotype. Various indices have been suggested in the literature for measuring integration level, yet their statistical properties
have remained mostly unstudied to date. In this study, I used simulations and resampling procedures in order to compare the
distributions and sampling properties of different indices. I simulated heterogeneous correlation matrices that ranged widely
in their integration level. I applied non-parametric bootstrapping to explore the effect of sampling on recovering the true
integration value of these matrices. In addition, I generated the statistical power space for one of the integration indices—the
relative standard deviation of the eigenvalues. The results show that the relative variance of eigenvalues maps exactly onto
the mean coefficient of determination, and that the index suggested by Hansen and Houle (J Evol Biol 21:1201–1219, 2008) is the same as Van Valen’s (J Theor Biol 45:235–247, 1974) redundancy index, both of which have some undesirable sampling properties that render them less useful in most practical
situations. Based on the power analysis, a sample of 30–40 specimens can be considered a sufficient minimum for most studies.
The R codes provided here can be utilized by other researchers to yield case-specific insights. 相似文献
11.
Brendon M. H. Larson 《Biological invasions》2007,9(8):947-956
Several authors have recently argued that invasion biologists should adopt a more objective and dispassionate stance towards
invasive species. Brown and Sax (Austral Ecol 29:530–536, 2004; Austral Ecol 30:481–483, 2005) assert that invasion biologists risk their objectivity, “commit the naturalist fallacy” or “embark on a slippery slope”
with engaged concern about invasive species. Elsewhere, Colautti and MacIsaac (Divers Distrib 10:135–141, 2004) propose a neutral language for invasion biology, one that insulates scientific from popular discussion about invasive species.
While there is certainly hyperbole about the effects of some invasive species, the type of objectivity promoted in these papers
may often be inappropriate for invasion biology. It implies a policy of non-action that is inconsistent with the conservation
values of many invasion biologists. To engage these values, invasion biologists can adopt deliberative methods for environmental
problem-solving that involve stakeholders in their research design and which still promote high standards of scientific rigor. 相似文献
12.
To be used as a predictive conservation tool, classification of animal habitats should rely on actual resource requirements
of individual species. Shreeve et al. (J Insect Conserv 5:145–161, 2001) produced a resource-based habitat classification for British butterflies, obtaining habitat association groups, whose constituent
species differed in their distribution extent, distribution change and vulnerability in Britain. To test the utility of this
approach for a group with a less-known biology, we produced a resource-based classification of habitats of Central European
macromoths. We worked with macrolepidopteran moth families, except for the megadiverse Geometridae and Noctuidae. We produced
a matrix of 178 life history attributes describing resource use by 164 species, subjected the matrix to ordination analysis,
and compared the resulting moths groupings with external ecological information. Five habitat association groups were distinguished:
I—close canopy moths, II—open canopy moths, III—grasslands moths, IV—herb-feeding hawk moths, and V—lichen feeders. The classification sustained deleting attributes related to host plants taxonomy. Groups I–III sustained control for taxonomic
positions of the moths, whereas IV and V did not. Members of the groups differed in the representation of externally obtained
habitat associations, biogeography elements, threat status, and range size. Endangered species were over-represented in groups
II and III and underrepresented in group I, in agreement with recent land cover changes across the continent. Species resources
can be used to reconstruct their habitat needs, and it is possible to scale up from life histories through habitat use to
range structures. 相似文献
13.
Here we address three misconceptions stated by Rice et al. in their observations of our article Paz-y-Mi?o and Espinosa (Evo
Edu Outreach 2:655–675, 2009), published in this journal. The five authors titled their note “The Theory of Evolution is Not an Explanation for the Origin of Life.” First, we argue that it is fallacious to believe that because the formulation of the theory of evolution, as conceived
in the 1800s, did not include an explanation for the origin of life, nor of the universe, the concept of evolution would not
allow us to hypothesize the possible beginnings of life and its connections to the cosmos. Not only Stanley Miller’s experiments
of 1953 led scientists to envision a continuum from the inorganic world to the origin and diversification of life, but also
Darwin’s own writings of 1871. Second, to dismiss the notion of Rice et al. that evolution does not provide explanations concerning
the universe or the cosmos, we identify compelling scientific discussions on the topics: Zaikowski et al. (Evo Edu Outreach
1:65–73, 2008), Krauss (Evo Edu Outreach 3:193–197, 2010), Peretó et al. (Orig Life Evol Biosph 39:395–406, 2009) and Follmann and Brownson (Naturwissenschaften 96:1265–1292, 2009). Third, although we acknowledge that the term Darwinism may not be inclusive of all new discoveries in evolution, and also that creationists and Intelligent Designers hijack the
term to portray evolution as ideology, we demonstrate that there is no statistical evidence suggesting that the word Darwinism
interferes with public acceptance of evolution, nor does the inclusion of the origin of life or the universe within the concept
of evolution. We examine the epistemological and empirical distinction between the theory of evolution and the concept of evolution and conclude that, although the distinction is important, it should not compromise scientific logic. 相似文献
14.
Alber M Glimm T Hentschel HG Kazmierczak B Zhang YT Zhu J Newman SA 《Bulletin of mathematical biology》2008,70(2):460-483
A recently proposed mathematical model of a “core” set of cellular and molecular interactions present in the developing vertebrate
limb was shown to exhibit pattern-forming instabilities and limb skeleton-like patterns under certain restrictive conditions,
suggesting that it may authentically represent the underlying embryonic process (Hentschel et al., Proc. R. Soc. B 271, 1713–1722, 2004). The model, an eight-equation system of partial differential equations, incorporates the behavior of mesenchymal cells as
“reactors,” both participating in the generation of morphogen patterns and changing their state and position in response to
them. The full system, which has smooth solutions that exist globally in time, is nonetheless highly complex and difficult
to handle analytically or numerically. According to a recent classification of developmental mechanisms (Salazar-Ciudad et
al., Development 130, 2027–2037, 2003), the limb model of Hentschel et al. is “morphodynamic,” since differentiation of new cell types occurs simultaneously with
cell rearrangement. This contrasts with “morphostatic” mechanisms, in which cell identity becomes established independently
of cell rearrangement. Under the hypothesis that development of some vertebrate limbs employs the core mechanism in a morphostatic
fashion, we derive in an analytically rigorous fashion a pair of equations representing the spatiotemporal evolution of the
morphogen fields under the assumption that cell differentiation relaxes faster than the evolution of the overall cell density
(i.e., the morphostatic limit of the full system). This simple reaction–diffusion system is unique in having been derived
analytically from a substantially more complex system involving multiple morphogens, extracellular matrix deposition, haptotaxis,
and cell translocation. We identify regions in the parameter space of the reduced system where Turing-type pattern formation
is possible, which we refer to as its “Turing space.” Obtained values of the parameters are used in numerical simulations
of the reduced system, using a new Galerkin finite element method, in tissue domains with nonstandard geometry. The reduced
system exhibits patterns of spots and stripes like those seen in developing limbs, indicating its potential utility in hybrid
continuum-discrete stochastic modeling of limb development. Lastly, we discuss the possible role in limb evolution of selection
for increasingly morphostatic developmental mechanisms. 相似文献
15.
Skúli Skúlason Kevin J. Parsons Richard Svanbck Katja Rsnen Moira M. Ferguson Colin E. Adams Per‐Arne Amundsen Pia Bartels Colin W. Bean Janette W. Boughman Gran Englund Jhannes Gubrandsson Oliver E. Hooker Alan G. Hudson Kimmo K. Kahilainen Rune Knudsen Bjarni K. Kristjnsson Camille A‐L. Leblanc Zophonías Jnsson Gunnar
hlund Carl Smith Sigurur S. Snorrason 《Biological reviews of the Cambridge Philosophical Society》2019,94(5):1786-1808
A major goal of evolutionary science is to understand how biological diversity is generated and altered. Despite considerable advances, we still have limited insight into how phenotypic variation arises and is sorted by natural selection. Here we argue that an integrated view, which merges ecology, evolution and developmental biology (eco evo devo) on an equal footing, is needed to understand the multifaceted role of the environment in simultaneously determining the development of the phenotype and the nature of the selective environment, and how organisms in turn affect the environment through eco evo and eco devo feedbacks. To illustrate the usefulness of an integrated eco evo devo perspective, we connect it with the theory of resource polymorphism (i.e. the phenotypic and genetic diversification that occurs in response to variation in available resources). In so doing, we highlight fishes from recently glaciated freshwater systems as exceptionally well‐suited model systems for testing predictions of an eco evo devo framework in studies of diversification. Studies on these fishes show that intraspecific diversity can evolve rapidly, and that this process is jointly facilitated by (i) the availability of diverse environments promoting divergent natural selection; (ii) dynamic developmental processes sensitive to environmental and genetic signals; and (iii) eco evo and eco devo feedbacks influencing the selective and developmental environments of the phenotype. We highlight empirical examples and present a conceptual model for the generation of resource polymorphism – emphasizing eco evo devo, and identify current gaps in knowledge. 相似文献
16.
It is usually assumed that new beneficial mutations are extremely rare. Yet, few experiments have been performed in multicellular
organisms that measure the effect of new beneficial mutations on viability and other measures of fitness. In most experiments,
it is difficult to clearly distinguish whether adaptations have occurred due to selection on new beneficial mutations or on
preexisting genetic variation. Using a modification of a Dobzhansky and Spassky (Evolution 1:191–216, 1947) assay to study change in viability over generations, we have observed an increase in viability in lines homozygous for the
second and third chromosomes of Drosophila melanogaster in 6–26 generations due to the occurrence of new beneficial mutations in population sizes of 20, 100 and 1,000. The lines
with the lowest initial viability responded the fastest to new beneficial mutations. These results show that new beneficial
mutations, along with selection, can quickly increase viability and fitness even in small populations. Hence, new advantageous
mutations may play an important role in adaptive evolution in higher organisms. 相似文献
17.
Extending Darwin’s analogy: Bridging differences in concepts of selection between farmers, biologists, and plant breeders 总被引:1,自引:0,他引:1
Darwin developed his theory of evolution based on an analogy between artificial selection by breeders of his day and “natural
selection.” For Darwin, selection included what biologists came to see as being composed of (1) phenotypic selection of individuals
based on phenotypic differences, and, when these are based on heritable genotypic differences, (2) genetic response between
generations, which can result in (3) evolution (cumulative directional genetic response over generations). The use of the
term “selection” in biology and plant breeding today reflects Darwin’s assumption—phenotypic selection is only biologically
significant when it results in evolution. In contrast, research shows that small-scale, traditionally-based farmers select
seed as part of an integrated production and consumption system in which selection is often not part of an evolutionary process,
but is still useful to farmers. Extending Darwin’s analogy to farmers can facilitate communication between farmers, biologists,
and plant breeders to improve selection and crop genetic resource conservation. 相似文献
18.
Biological systems are inherently noisy. Predicting the outcome of a perturbation is extremely challenging. Traditional reductionist
approach of describing properties of parts, vis-a-vis higher level behaviour has led to enormous understanding of fundamental
molecular level biology. This approach typically consists of converting genes into junk (knock-down) and garbage (knock-out)
and observe how a system responds. To enable broader understanding of biological dynamics, an integrated computational and
experimental strategy was formally proposed in mid 1990s leading to the re-emergence of Systems Biology. However, soon it
became clear that natural systems were far more complex than expected. A new strategy to address biological complexity was
proposed at MIT (Massachusetts Institute of Technology) in June 2004, when the first meeting of synthetic biology was held.
Though the term ‘synthetic biology’ was proposed during 1970s (Szybalski in Control of gene expression, Plenum Press, New
York, 1974), the usage of the original concept found an experimental proof in 2000 with the demonstration of a three-gene circuit called
repressilator (Elowitz and Leibler in Nature, 403:335–338, 2000). This encouraged people to think of forward engineering biology from a set of well described parts. 相似文献
19.
Giambattista Brocchi’s (1814) monograph (see Dominici, Evo Edu Outreach, this issue, 2010) on the Tertiary fossils of the Subappenines in Italy—and their relation to the living molluscan fauna—contains a theoretical,
transmutational perspective (“Brocchian transmutation”). Unlike Lamarck (1809), Brocchi saw species as discrete and fundamentally stable entities. Explicitly analogizing the births and deaths of species
with those of individual organisms (“Brocchi’s analogy”), Brocchi proposed that species have inherent longevities, eventually
dying of old age unless driven to extinction by external forces. As for individuals, births and deaths of species are understood
to have natural causes; sequences of births and deaths of species produce genealogical lineages of descent, and faunas become
increasingly modernized through time. Brocchi calculated that over 50% of his fossil species are still alive in the modern
fauna. Brocchi’s work was reviewed by Horner (1816) in Edinburgh. Brocchi’s influence as a transmutational thinker is clear in Jameson’s (1827) “geological illustrations” in his fifth edition of his translation of Cuvier’s Theory of the Earth (read by his student Charles Darwin) and in the anonymous essays of 1826 and 1827 published in the Edinburgh New Philosophical Journal—which also carried a notice of Brocchi’s death in 1827. The notion that new species replace older, extinct ones—in what today
would be called an explicitly phylogenetic context—permeates these essays. Herschel’s (1830) discussion of temporal replacement of species and the modernization of faunas closely mirrors these prior discussions. His
book, dedicated to the search for natural causes of natural phenomena, was read by Charles Darwin while a student at Cambridge.
Darwin’s work on HMS Beagle was in large measure an exploration of replacement patterns of “allied forms” of endemic species
in time and in space. His earliest discussions of transmutation, in his essay February 1835, as well as the Red Notebook and the early pages of Notebook B (the latter two written in 1837 back in England), contain Brocchi’s analogy, including
the idea of inherent species longevities. Darwin’s first theory of the origin of species was explicitly saltational, invoking
geographic isolation as the main cause of the abrupt appearance of new species. We conclude that Darwin was testing the predicted
patterns of both Brocchian and Lamarckian transmutation as early as 1832 at the outset of his work on the Beagle. 相似文献
20.
The main objective of this study was to analyze the differences in profiles of RNase activities from triticale embryos (Triticosecale, cv. Ugo) between dormant and non-dormant caryopses and to determine the influence of exogenous abscisic acid (ABA) on the
activities of these enzymes. The major RNase from the examined tissue was detected following SDS-PAGE, with substrate-based
gel assay, described by Yen and Green (Plant Physiol 97:1487–1493, 1991). The activities of enzymes were characterized according to their pH optima, ion dependence, EDTA sensitivity and DNase activity.
In embryos with arrested growth (in a natural way by dormancy or artificially by ABA treatment), the activity of two enzymes—24
and 27 kDa—belonging to class I RNases was completely inhibited, whereas that of two other RNases of this family—23 and 25 kDa—was
detectable. However, the activity of the class I ribonucleases (enzymes responsible for cellular Pi release) was very low. Moreover, in contrast with non-dormant caryopses, imbibing embryos of dormant or ABA-treated seeds
contained 13- and 14-kDa enzymes. These enzymes have not been classified so far, and their specific properties are different
from the generally accepted properties of ribonucleolytic enzymes. In addition to the above results, the Pi content in the analyzed samples was determined by the Ames (Methods Enzymol 8:115–118, 1966) method. The results suggest a very low and constant level of inorganic phosphate in dormant samples as well as an evidently
decreasing Pi content in embryos under the influence of ABA treatment. The inhibition of the class I RNases activity induced by abscisic
acid implies that one of the roles of ABA in seed dormancy may consist in arresting the catabolic release of Pi, which results in retarding the embryo’s growth. 相似文献