Intimate Ark

2017 ◽  
Author(s):  
John L. Culliney ◽  
David Jones
Keyword(s):  
Sexual Selection ◽  
Genetic Recombination ◽  
Life Forms ◽  
Mating Pair ◽  
Genetic Contribution ◽  
Substantial Portion ◽  
Genetic Makeup ◽  
Eukaryotic Organisms ◽  
New Generation ◽  
Gene Sharing

Among the greatest cooperative examples of biotic evolution that released a virtually unbounded world of complexity, particularly conspicuous among eukaryotic organisms, was the evolution of sex. In sex, each individual of a mating pair contributes part of its genetic makeup (genome) to offspring—always cells are the seminal agents of the genetic contribution from each self—that participate in an emergent new generation. Thus a self, upon engaging in sex, abandons a substantial portion of its integrity and weaves together a molecular-to-cellular-to-organismal fractal interface with a partner. Throughout the sexual world, self seeks a profound intimacy with non-self. The chapter first describes gene sharing by bacteria through conjugation, a prokaryotic version of sex. An allegory of dancing snakes metaphorically represents cellular reproduction by mitosis and the reduction divisions of chromosomes in meiosis, the basis of gene sharing in sex among eukaryotes. Genetic recombination via meiosis enormously accelerates the diverse expressions of myriad life forms. Among angiosperm plants, sex is manifest in immensely variable flowers and, with some exceptions, their colors and forms evolved in response to a profound cooperative imperative with animal partners that spread their pollen. Darwin’s major insight on sexual selection among animals has explained male-female dimorphisms from subtle to spectacular.

scholarly journals Endosymbiotic Evolution of Algae, Secondary Heterotrophy and Parasitism

Biomolecules ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 266 ◽  
Author(s):  
Oborník
Keyword(s):  
Electron Transport Chain ◽  
Photosynthetic Electron Transport ◽  
Life Forms ◽  
Biochemical Process ◽  
Photosynthetic Electron Transport Chain ◽  
Transport Chain ◽  
Ultimate Source ◽  
Constructive Evolution ◽  
Eukaryotic Organisms ◽  
Endosymbiotic Evolution

Photosynthesis is a biochemical process essential for life, serving as the ultimate source of chemical energy for phototrophic and heterotrophic life forms. Since the machinery of the photosynthetic electron transport chain is quite complex and is unlikely to have evolved multiple independent times, it is believed that this machinery has been transferred to diverse eukaryotic organisms by endosymbiotic events involving a eukaryotic host and a phototrophic endosymbiont. Thus, photoautotrophy, as a benefit, is transmitted through the evolution of plastids. However, many eukaryotes became secondarily heterotrophic, reverting to hetero-osmotrophy, phagotrophy, or parasitism. Here, I briefly review the constructive evolution of plastid endosymbioses and the consequential switch to reductive evolution involving losses of photosynthesis and plastids and the evolution of parasitism from a photosynthetic ancestor.

On the Emergence of Intersexual Selection: Arbitrary Trait Preference Improves Female-Male Coevolution

2021 ◽  
pp. 1-11
Author(s):  
Larry Bull
Keyword(s):  
Sexual Selection ◽  
Fitness Landscape ◽  
Fundamental Aspect ◽  
Mating Types ◽  
Selection Mechanism ◽  
Trait Preference ◽  
Landscape Size ◽  
Eukaryotic Organisms

Abstract Sexual selection is a fundamental aspect of evolution for all eukaryotic organisms with mating types. This article suggests intersexual selection is best viewed as a mechanism with which to compensate for the unavoidable dynamics of coevolution between sexes that emerge with isogamy. Using the NKCS model it is shown by varying fitness landscape size, ruggedness, and connectedness, how a purely arbitrary trait preference sexual selection mechanism proves beneficial with high dependence between the sexes. This is found to be the case whether one or both sexes exploit such intersexual selection.

Mitonuclear mate choice

2019 ◽  
pp. 179-198
Author(s):  
Geoffrey E. Hill
Keyword(s):  
Sexual Selection ◽  
Mate Choice ◽  
Sexual Reproduction ◽  
Significant Role ◽  
Mitochondrial Genes ◽  
Cellular Respiration ◽  
New Combinations ◽  
New Generation

At each new generation, sexual reproduction creates new combinations of nuclear and mitochondrial genes, and the potential arises for mitonuclear incompatibilities and reduced fitness. Sexual selection plays a key role in maintaining mitonuclear coadaptation across generations because it enables pre-zygotic sorting for coadapted mitonuclear genotypes. In this chapter, I present data that individuals engaged in mate choice select partners with correct species-typical mitochondrial and nuclear genotypes as well as individuals with highly functional cellular respiration. The implication is that mate choice for compatible nuclear and mitochondrial genes can play a significant role in generating the patterns of ornamentation and preferences observed in animals.

Flow Cytometry and Cell Sorting in Plant Biotechnology

2005 ◽  
Author(s):  
David W. Galbraith ◽  
Jan BartoŠ
Keyword(s):  
Dna Sequences ◽  
Molecular Mechanisms ◽  
Higher Plants ◽  
Flow Cytometric Analysis ◽  
Nuclear Genome ◽  
Plant Biotechnology ◽  
Biomass Accumulation ◽  
Life Forms ◽  
Dietary Factors ◽  
Eukaryotic Organisms

Higher plants comprise approximately 250,000 described species and represent a critical component of the planetary biomass. They contribute functions essential for life, of which the most important is photosynthesis, as it provides the means for conversion of incident solar radiation into biomass accumulation, as well as the oxygen required by aerobic life forms. Fixed carbon in the form of carbohydrate provides the basis of the food chain, and metabolic interconversions within plants provide a variety of essential dietary factors. Plants also provide biomass in the form of structural materials and are the source of many natural products with important biomedical properties. As a consequence, considerable scientific interest is invested in determining the molecular mechanisms underlying plant growth, development, metabolism, and responses to biotic and abiotic stresses. Investment has also been made in developing tools and resources for biological investigations using plants. Notable advances include the development of genetics, of means for transformation using defined DNA sequences, and most recently, of the entire nuclear genome sequences of two plant species (Arabidopsis thaliana and Oryza sativa). On the basis of information of this type and that from other sources, it is evident that higher plants share many features with other eukaryotic organisms. Shared features can be observed at many levels; for example, the overall method of construction of cells, in which a bilamellar plasma membrane separates the cytoplasm from the external milieu and provides primary homeostatic regulation. Eukaryotic cells of different kingdoms share organelles, as well as overall regulatory mechanisms. Shared, or highly similar, protein sequences are observed, and they perform similar functions as enzymes, regulatory molecules, or structural components . Higher land plants have evident differences from other eukaryotes. They contain unique classes of organelles primarily devoted to energy capture from sunlight (plastids and peroxisomes). Of these, chloroplasts contain highly fluorescent pigments devoted to photosynthesis, which, particularly chlorophyll, provide unique and powerful signals that can be employed for flow cytometric analysis. Higher plants are also essentially immobile in the sporophytic stage and hence must be capable of responding to changes in environmental conditions and to biotic attack.

scholarly journals Male Hemolymph Loss During Nuptial Feeding as a Proximate Mechanisim Underlying the Virgin-Male Mating Advantage in Sagebrush Crickets

2003 ◽  
Vol 27 ◽  
pp. 45-50
Author(s):  
Scott Sakaluk ◽  
Mark Campbell ◽  
Peter Keorpes ◽  
Andrew Clark
Keyword(s):  
Sexual Selection ◽  
Male Mating ◽  
Energy Reserves ◽  
Substantial Portion ◽  
Mating Advantage ◽  
Virgin Male ◽  
Cyphoderris Strepitans ◽  
Two Alternatives ◽  
Signaling Activity ◽  
Spermatophore Production

Male sagebrush crickets, Cyphoderris strepitans, offer an unusual nuptial food gift to females during mating: females chew on the ends of the males' fleshy hind wings and ingest hemolymph seeping from the wounds they inflict. Previous studies have shown that once a male had mated, his probability of obtaining an additional copulation is reduced relative to that of a virgin male seeking to secure his first mating, a pattern known as the virgin­male mating advantage. One hypothesis to account for the virgin-male mating advantage is that non­virgin males, having lost a substantial portion of their energy reserves at mating, may be unable to sustain the costly acoustical signaling activity required for the passive attraction of additional females. If the future mating prospects of non-virgin males are diminished because of sexual fatigue, this could stem either from the resources required to manufacture a new spermatophore or through the energy needed to replenish haemolymph lost through female wing­feeding. To distinguish between these two alternatives, we experimentally depleted virgin males of varying amounts haemolymph (0, 5 and 10 ul) in a way that mimicked hemolymph loss of non-virgin males, without the attendant costs of spermatophore production. After they had been treated, males were released in the field and recaptured over the course of the breeding season to monitor their mating success. Control males mated significantly sooner than did males depleted of 5 or 10 ul of hemolymph. We conclude, therefore, that the depletion of hemolymph that occurs through female wing feeding is sufficient by itself to diminish a non-virgin male's ability to secure another mating, acting as a brake on the operation of sexual selection in this species.

scholarly journals The maternal genetic make-up of the Iberian Peninsula between the Neolithic and the Early Bronze Age

2017 ◽  
Author(s):  
Anna Szécsényi-Nagy ◽  
Christina Roth ◽  
Guido Brandt ◽  
Cristina Rihuete-Herrada ◽  
Cristina Tejedor-Rodríguez ◽  
...  
Keyword(s):  
Iberian Peninsula ◽  
Bronze Age ◽  
Population History ◽  
Early Bronze Age ◽  
Genetic Contribution ◽  
Early Neolithic ◽  
Hunter Gatherers ◽  
Late Chalcolithic ◽  
History Of ◽  
Genetic Makeup

AbstractAgriculture first reached the Iberian Peninsula around 5700 BCE. However, little is known about the genetic structure and changes of prehistoric populations in different geographic areas of Iberia. In our study, we focused on the maternal genetic makeup of the Neolithic (∼ 5500-3000 BCE), Chalcolithic (∼ 3000-2200 BCE) and Early Bronze Age (∼ 2200-1500 BCE). We report ancient mitochondrial DNA results of 213 individuals (151 HVS-I sequences) from the northeast, central, southeast and southwest regions and thus on the largest archaeogenetic dataset from the Peninsula to date. Similar to other parts of Europe, we observe a discontinuity between hunter-gatherers and the first farmers of the Neolithic. During the subsequent periods, we detect regional continuity of Early Neolithic lineages across Iberia, however the genetic contribution of hunter-gatherers is generally higher than in other parts of Europe and varies regionally. In contrast to ancient DNA findings from Central Europe, we do not observe a major turnover in the mtDNA record of the Iberian Late Chalcolithic and Early Bronze Age, suggesting that the population history of the Iberian Peninsula is distinct in character.

Influence of Cell Wall Composition on the Fossilisation of Bacteria and the Implications for the Search for Early Life Forms

1997 ◽  
Vol 161 ◽  
pp. 491-504 ◽  
Author(s):  
Frances Westall
Keyword(s):  
Cell Wall ◽  
Life Forms ◽  
Cation Binding ◽  
Positive Bacterium ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Transmission Electron ◽  
Hydrothermal Sediments ◽  
Identification Of Bacteria ◽  
The Difference

AbstractThe oldest cell-like structures on Earth are preserved in silicified lagoonal, shallow sea or hydrothermal sediments, such as some Archean formations in Western Australia and South Africa. Previous studies concentrated on the search for organic fossils in Archean rocks. Observations of silicified bacteria (as silica minerals) are scarce for both the Precambrian and the Phanerozoic, but reports of mineral bacteria finds, in general, are increasing. The problems associated with the identification of authentic fossil bacteria and, if possible, closer identification of bacteria type can, in part, be overcome by experimental fossilisation studies. These have shown that not all bacteria fossilise in the same way and, indeed, some seem to be very resistent to fossilisation. This paper deals with a transmission electron microscope investigation of the silicification of four species of bacteria commonly found in the environment. The Gram positiveBacillus laterosporusand its spore produced a robust, durable crust upon silicification, whereas the Gram negativePseudomonas fluorescens, Ps. vesicularis, andPs. acidovoranspresented delicately preserved walls. The greater amount of peptidoglycan, containing abundant metal cation binding sites, in the cell wall of the Gram positive bacterium, probably accounts for the difference in the mode of fossilisation. The Gram positive bacteria are, therefore, probably most likely to be preserved in the terrestrial and extraterrestrial rock record.

Finding the Right Problems: Some HREM Applications to Interfaces

1984 ◽  
Vol 42 ◽  
pp. 376-379
Author(s):  
D. Cherns
Keyword(s):  
Grain Boundaries ◽  
High Resolution Electron Microscopy ◽  
Boundary Structure ◽  
Atomic Structures ◽  
Grain Boundary Structure ◽  
Resolution Electron ◽  
Point To Point ◽  
The Right ◽  
New Generation ◽  
Better Than

The use of high resolution electron microscopy (HREM) to determine the atomic structure of grain boundaries and interfaces is a topic of great current interest. Grain boundary structure has been considered for many years as central to an understanding of the mechanical and transport properties of materials. Some more recent attention has focussed on the atomic structures of metalsemiconductor interfaces which are believed to control electrical properties of contacts. The atomic structures of interfaces in semiconductor or metal multilayers is an area of growing interest for understanding the unusual electrical or mechanical properties which these new materials possess. However, although the point-to-point resolutions of currently available HREMs, ∼2-3Å, appear sufficient to solve many of these problems, few atomic models of grain boundaries and interfaces have been derived. Moreover, with a new generation of 300-400kV instruments promising resolutions in the 1.6-2.0 Å range, and resolutions better than 1.5Å expected from specialist instruments, it is an appropriate time to consider the usefulness of HREM for interface studies.

Total etch dentin bonding systems: scanning electron microscopy of the resin-dentin hybrid layer

1992 ◽  
Vol 50 (2) ◽  
pp. 1092-1093
Author(s):  
Jorge Perdigao
Keyword(s):  
Composite Resin ◽  
Mechanical Interlocking ◽  
Hybrid Layer ◽  
Agent Based ◽  
Dentin Bonding ◽  
Acid Agent ◽  
Bond Strengths ◽  
Main Component ◽  
Bonding Systems ◽  
New Generation

In 1955, Buonocore introduced the etching of enamel with phosphoric acid. Bonding to enamel was created by mechanical interlocking of resin tags with enamel prisms. Enamel is an inert tissue whose main component is hydroxyapatite (98% by weight). Conversely, dentin is a wet living tissue crossed by tubules containing cellular extensions of the dental pulp. Dentin consists of 18% of organic material, primarily collagen. Several generations of dentin bonding systems (DBS) have been studied in the last 20 years. The dentin bond strengths associated with these DBS have been constantly lower than the enamel bond strengths. Recently, a new generation of DBS has been described. They are applied in three steps: an acid agent on enamel and dentin (total etch technique), two mixed primers and a bonding agent based on a methacrylate resin. They are supposed to bond composite resin to wet dentin through dentin organic component, forming a peculiar blended structure that is part tooth and part resin: the hybrid layer.

Low-voltage, high-resolution scanning electron microscopy of polymers

1987 ◽  
Vol 45 ◽  
pp. 466-467 ◽  
Author(s):  
S. J. Krause ◽  
W.W. Adams ◽  
S. Kumar ◽  
T. Reilly ◽  
T. Suziki
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Voltage ◽  
Chromatic Aberration ◽  
Image Resolution ◽  
Resolution Limit ◽  
Crossover Point ◽  
New Generation ◽  
Beam Damage ◽  
Scanning Electron

Scanning electron microscopy (SEM) of polymers at routine operating voltages of 15 to 25 keV can lead to beam damage and sample image distortion due to charging. Imaging polymer samples with low accelerating voltages (0.1 to 2.0 keV), at or near the “crossover point”, can reduce beam damage, eliminate charging, and improve contrast of surface detail. However, at low voltage, beam brightness is reduced and image resolution is degraded due to chromatic aberration. A new generation of instruments has improved brightness at low voltages, but a typical SEM with a tungsten hairpin filament will have a resolution limit of about 100nm at 1keV. Recently, a new field emission gun (FEG) SEM, the Hitachi S900, was introduced with a reported resolution of 0.8nm at 30keV and 5nm at 1keV. In this research we are reporting the results of imaging coated and uncoated polymer samples at accelerating voltages between 1keV and 30keV in a tungsten hairpin SEM and in the Hitachi S900 FEG SEM.

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