scholarly journals Oxygen, temperature and the deep-marine stenothermal cradle of Ediacaran evolution

2018 ◽  
Vol 285 (1893) ◽  
pp. 20181724 ◽  
Author(s):  
Thomas H. Boag ◽  
Richard G. Stockey ◽  
Leanne E. Elder ◽  
Pincelli M. Hull ◽  
Erik A. Sperling
Keyword(s):  
Gas Exchange ◽  
Fossil Record ◽  
Synergistic Effects ◽  
Critical Role ◽  
Narrow Temperature Range ◽  
Ediacara Biota ◽  
Oceanographic Data ◽  
Effects Of Temperature ◽  
Species Specific ◽  
Water Facies

Ediacaran fossils document the early evolution of complex megascopic life, contemporaneous with geochemical evidence for widespread marine anoxia. These data suggest early animals experienced frequent hypoxia. Research has thus focused on the concentration of molecular oxygen (O 2 ) required by early animals, while also considering the impacts of climate. One model, the Cold Cradle hypothesis, proposed the Ediacaran biota originated in cold, shallow-water environments owing to increased O 2 solubility. First, we demonstrate using principles of gas exchange that temperature does have a critical role in governing the bioavailability of O 2 —but in cooler water the supply of O 2 is actually lower. Second, the fossil record suggests the Ediacara biota initially occur approximately 571 Ma in deep-water facies, before appearing in shelf environments approximately 555 Ma. We propose an ecophysiological underpinning for this pattern. By combining oceanographic data with new respirometry experiments we show that in the shallow mixed layer where seasonal temperatures fluctuate widely, thermal and partial pressure ( p O 2 ) effects are highly synergistic. The result is that temperature change away from species-specific optima impairs tolerance to low p O 2 . We hypothesize that deep and particularly stenothermal (narrow temperature range) environments in the Ediacaran ocean were a physiological refuge from the synergistic effects of temperature and low p O 2 .

scholarly journals Role of Pulmonary Surfactant in Gas Exchange Mechanism and Providing Protection against Progression of any Respiratory Viral Disease like SARS-CoV-2 and Need to focus it as First Point of Medication for all Respiratory Diseases

2021 ◽  
Author(s):  
Makarand Phadke
Keyword(s):  
Gas Exchange ◽  
Pulmonary Surfactant ◽  
Vaccine Development ◽  
Critical Role ◽  
Physical Property ◽  
Lower Surface ◽  
Viral Disease ◽  
Type I ◽  
Mucosal Layer ◽  
Unique Physical Property

Abstract During inhalation oxygen molecules are drawn towards type I cells. The partial pressure difference and solubility factor act as a Drive for this movement of oxygen molecules.It is well known that the pulmonary surfactant plays an important role in gas exchange. The surfactant is thin mono-layer. The top surface of surfactant with SP-B and C proteins faces alveolar air and is hydrophobic in nature and acts as a surface tension reducer, whereas lower surface with SP-A and D proteins, is hydrophilic and is adsorbed on mucosal layer. This lower surface of surfactant acts as an anti invader, pathogen barrier. However there is a small missing link in explaining its exact mechanism or role in justifying these properties during normal conditions and during ‘viral ligand’ attack.Similarly a unique physical property of SP- C component is listed in research papers; however its application is not researched anywhere. SP-C has a dielectric constant of 2 to 3 and plays a very critical role in drastically reducing progression of any respiratory viral disease including SARS-CoV-2. This hypothesis targets to explain both micro mechanisms with the help of basic laws of physics, and fluid mechanics. The figures/sketches, drawn also depict the physics involved and not much of a physiology or genetic codes etc. Two examples, in the industry, are briefly listed in the last paragraphs to draw some parallel with above mechanisms.Vaccination is a proven method for containment of a particular respiratory viral disease, if not its cure. But if focus is also given on health of pulmonary surfactant with respect to pathogenesis of any respiratory viral disease, and development of a broad spectrum medication on it; probable loss of lot many lives can be avoided and vaccine development and vaccination management related issues can be less panicky.

Sexual Selection, Timing and an X–Y Homologous Gene: Did Homo Sapiens Speciate on the Y Chromosome?

2004 ◽  
Author(s):  
Tim J. Crow
Keyword(s):  
Sexual Selection ◽  
Sex Chromosome ◽  
Homo Sapiens ◽  
Single Gene ◽  
Critical Role ◽  
Hominid Evolution ◽  
Homologous Gene ◽  
Chromosomal Change ◽  
Species Specific ◽  
Sex Chromosome Aneuploidies

This chapter provides a theory of the speciation of modern Homo sapiens, that a single gene played a critical role in the transition from a precursor species. The theory is founded upon the following: firstly, the premise that hemispheric asymmetry is the defining feature of the human brain and the only plausible correlate of language; secondly, an argument for a specific candidate region (the Xq21.3/Yp11.2 region of homology) based upon the reciprocal deficits associated with the sex chromosome aneuploidies, and the course of chromosomal change in hominid evolution; and thirdly, a particular evolutionary mechanism (sexual selection acting on an X-Y-linked gene) to account for species-specific modification of what initially was a saltational change. These postulates relate to the case of modern Homo sapiens. On the basis of the recent literature, the discussion argues that the third premise has general significance as a mechanism of speciation.

EFFECTS OF TEMPERATURE AND POTASSIUM CHLORATE ON LEAF GAS EXCHANGE AND FLOWERING IN LONGAN

2010 ◽  
pp. 323-328 ◽  
Author(s):  
C. Sritontip ◽  
P. Tiyayon ◽  
M. Hegele ◽  
P. Sruamsiri ◽  
D. Naphrom ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Leaf Gas Exchange ◽  
Potassium Chlorate ◽  
Effects Of Temperature

The effects of temperature on the gas exchange cycle in Agathemera crassa

2015 ◽  
Vol 183 ◽  
pp. 126-130 ◽  
Author(s):  
Mariana Thienel ◽  
Mauricio Canals ◽  
Francisco Bozinovic ◽  
Claudio Veloso
Keyword(s):  
Gas Exchange ◽  
Effects Of Temperature

scholarly journals Constructional and functional anatomy of Ediacaran rangeomorphs

2020 ◽  
pp. 1-12
Author(s):  
Nicholas J Butterfield
Keyword(s):  
Fluid Dynamics ◽  
Gas Exchange ◽  
Organic Carbon ◽  
Fossil Record ◽  
White Sea ◽  
Functional Anatomy ◽  
Food Delivery ◽  
The White Sea ◽  
Total Group ◽  
Taphonomic Analysis

Abstract Ediacaran rangeomorphs were the first substantially macroscopic organisms to appear in the fossil record, but their underlying biology remains problematic. Although demonstrably heterotrophic, their current interpretation as osmotrophic consumers of dissolved organic carbon (DOC) is incompatible with the inertial (high Re) and advective (high Pe) fluid dynamics accompanying macroscopic length scales. The key to resolving rangeomorph feeding and physiology lies in their underlying construction. Taphonomic analysis of three-dimensionally preserved Charnia from the White Sea identifies the presence of large, originally water-filled compartments that served both as a hydrostatic exoskeleton and semi-isolated digestion chambers capable of processing recalcitrant substrates, most likely in conjunction with a resident microbiome. At the same time, the hydrodynamically exposed outer surface of macroscopic rangeomorphs would have dramatically enhanced both gas exchange and food delivery. A bag-like epithelium filled with transiently circulated seawater offers an exceptionally efficient means of constructing a simple, DOC-consuming, multicellular heterotroph. Such a body plan is broadly comparable to that of anthozoan cnidarians, minus such derived features as muscle, tentacles and a centralized mouth. Along with other early bag-like fossils, rangeomorphs can be reliably identified as total-group eumetazoans, potentially colonial stem-group cnidarians.

scholarly journals Factors influencing test porosity in planktonic foraminifera

2018 ◽  
Vol 15 (21) ◽  
pp. 6607-6619 ◽  
Author(s):  
Janet E. Burke ◽  
Willem Renema ◽  
Michael J. Henehan ◽  
Leanne E. Elder ◽  
Catherine V. Davis ◽  
...  
Keyword(s):  
Fossil Record ◽  
Pore Space ◽  
Planktonic Foraminifera ◽  
Critical Role ◽  
Environmental Drivers ◽  
Geochemical Data ◽  
Test Surface ◽  
Metabolic Rates ◽  
Pore Characteristics ◽  
Test Volume

Abstract. The clustering of mitochondria near pores in the test walls of foraminifera suggests that these perforations play a critical role in metabolic gas exchange. As such, pore measurements could provide a novel means of tracking changes in metabolic rate in the fossil record. However, in planktonic foraminifera, variation in average pore area, density, and porosity (the total percentage of a test wall that is open pore space) have been variously attributed to environmental, biological, and taxonomic drivers, complicating such an interpretation. Here we examine the environmental, biological, and evolutionary determinants of pore characteristics in 718 individuals, representing 17 morphospecies of planktonic foraminifera from 6 core tops in the North Atlantic. Using random forest models, we find that porosity is primarily correlated to test surface area, test volume, and habitat temperature, key factors in determining metabolic rates. In order to test if this correlation arose spuriously through the association of cryptic species with distinct biomes, we cultured Globigerinoides ruber in three different temperature conditions, and found that porosity increased with temperature. Crucially, these results show that porosity can be plastic: changing in response to environmental drivers within the lifetime of an individual foraminifer. This demonstrates the potential of porosity as a proxy for foraminiferal metabolic rates, with significance for interpreting geochemical data and the physiology of foraminifera in non-analog environments. It also highlights the importance of phenotypic plasticity (i.e., ecophenotypy) in accounting for some aspects of morphological variation in the modern and fossil record.

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