A case for low atmospheric oxygen levels during Earth's middle history

2018 ◽  
Vol 2 (2) ◽  
pp. 149-159 ◽  
Author(s):  
Noah J. Planavsky ◽  
Devon B. Cole ◽  
Terry T. Isson ◽  
Christopher T. Reinhard ◽  
Peter W. Crockford ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Conceptual Framework ◽  
Environmental Conditions ◽  
Atmospheric Oxygen ◽  
Critical Factor ◽  
Planetary Surface ◽  
Surface Oxygen ◽  
Oxygen Levels ◽  
Early Diversification ◽  
Atmospheric Level

The oxygenation of the atmosphere — one of the most fundamental transformations in Earth's history — dramatically altered the chemical composition of the oceans and provides a compelling example of how life can reshape planetary surface environments. Furthermore, it is commonly proposed that surface oxygen levels played a key role in controlling the timing and tempo of the origin and early diversification of animals. Although oxygen levels were likely more dynamic than previously imagined, we make a case here that emerging records provide evidence for low atmospheric oxygen levels for the majority of Earth's history. Specifically, we review records and present a conceptual framework that suggest that background oxygen levels were below 1% of the present atmospheric level during the billon years leading up to the diversification of early animals. Evidence for low background oxygen levels through much of the Proterozoic bolsters the case that environmental conditions were a critical factor in controlling the structure of ecosystems through Earth's history.

scholarly journals Atmospheric oxygenation of the early earth and earth-like planets driven by competition between land and seafloor weathering

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Yasuto Watanabe ◽  
Eiichi Tajika
Keyword(s):  
Chemical Weathering ◽  
Atmospheric Oxygen ◽  
Oxygenic Photosynthesis ◽  
Biogeochemical Model ◽  
Planetary Surface ◽  
Oxygen Levels ◽  
Earth Like Planets ◽  
Continental Weathering ◽  
Continental Growth ◽  
Marine Biosphere

AbstractOxygen is a potential biosignature for terrestrial Earth-like planets. The primary source of oxygen on Earth is oxygenic photosynthesis, which may be limited by the supply of riverine phosphorus. Therefore, phosphorus supply from the chemical weathering of continents is crucial for the evolution of pO2. Chemical weathering occurs on both the continents and seafloor and stabilizes the climate, but phosphorus is only supplied by continental weathering. The amount of continental weathering relative to seafloor weathering may be critical for primary productivity and pO2. The area of continents could change as a result of continental growth and the amount of ocean mass on the planetary surface, and these factors could be very different on extrasolar Earth-like planets. Here, we investigated the effects of continental and seafloor weathering on the atmospheric oxygen levels, in terms of the Earth-like phosphorus-limited marine biosphere. We used a simple biogeochemical model and investigated a possible relationship between continental growth and atmospheric oxygen levels. We found that the atmosphere could evolve totally different redox conditions (an abrupt rise of atmospheric oxygen levels or a reducing condition to form organic haze) caused by continental growth, which changes the relative contribution of silicate weathering feedback from seafloor to continent. We also found that conditions with lower solar luminosity and a larger land fraction provided a preferable condition for the phosphorus-limited marine biosphere to produce high levels of oxygen in the atmosphere. We also found that the atmospheric oxygen level is strongly affected by the activity of the anaerobic marine microbial ecosystem. Our results suggest that the area of land on the planetary surface may be crucial for achieving high oxygen levels in a phosphorus-limited marine biosphere. These results contribute to the fundamental understanding of the general behaviors of Earth-like planets with oceans and an Earth-like marine biosphere.

scholarly journals Variability in chemical composition and antimicrobial activity of essential oil of Rosa × damascena Herrm. from mountainous regions of Iran

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Mansureh Ghavam ◽  
Afsaneh Afzali ◽  
Maria Manconi ◽  
Gianluigi Bacchetta ◽  
Maria Letizia Manca
Keyword(s):  
Antimicrobial Activity ◽  
Chemical Composition ◽  
Essential Oil ◽  
Essential Oils ◽  
Environmental Conditions ◽  
Raw Materials ◽  
Rosa Damascena ◽  
Mountainous Regions ◽  
Aspergillus Brasiliensis ◽  
Suitable Area

Abstract Background Essential oil of Rosa × damascena Herrm. is one of the most valuable and important raw materials for the flavor and fragrance industry. The cultivation of this plant has ancient origins, and Kashan was one of the first mountainous regions of Iran dealing with the cultivation of R. × damascena. In this study, both chemical composition and antimicrobial activity of different rose essential oils obtained from five mountainous areas of Kashan region (Maragh, Qamsar, Sadeh, Javinan, and Kamoo) has been investigated along with the influence of the environmental conditions on these properties. Results Results showed that yield and chemical composition of essential oils obtained from Rosa × damascena were significantly affected by the collection area. In particular, the yield of oils varied from ~0.08 to ~0.132% and citronellol (36.70-9.18%), geraniol (12.82-0.47%), nonadecane (22.73-10.36%), heneicosane (31.7-11.43%), and 1-nonadecene (6.03-3.93%) have been detected as main compounds in all the plants collected, but at different concentrations depending on the collection area. The best fragrance and the highest yield were found in the oil from Kamoo area. Similarly to the chemical composition, the antimicrobial activity of the essential oils was affected by their origin, and essential oil obtained from plants collected from Kamoo area disclosed the highest antibacterial and antifungal efficacy. Its inhibition halos were 17.33±0.58 mm against Aspergillus brasiliensis, 15.67±0.58 mm against Staphylococcus aureus, and 12.33±0. 58 mm against Streptococcus pyogenes. Essential oils of R. damascena were also effective against Gram-negative Pseudomonas aeruginosa and they had a MIC value of 62.50 μg/mL irrespective of the collection area (except the oil from Javinan area). On the contrary, the highest antifungal power against Candida albicans yeast was reached using the essential oil obtained from plants collected in Javinan region (MIC and MBC ~62.50 μg/mL). Conclusions Overall results underline the influence of environmental conditions of the different areas of Kashan region, on the chemical composition of and antimicrobial activity of the essential oils of Rosa × damascena. In addition, results disclosed that Kamoo seemed to be the most suitable area for the competitive cultivation of R. × damascena to the intensive production of aromatic flower oil and natural antimicrobial essential oils.

scholarly journals Facilitation costs and benefits function simultaneously on stress gradients for animals

2018 ◽  
Vol 285 (1885) ◽  
pp. 20180983 ◽  
Author(s):  
Olivier Dangles ◽  
Mario Herrera ◽  
Carlos Carpio ◽  
Christopher J. Lortie
Keyword(s):  
Conceptual Framework ◽  
Environmental Conditions ◽  
Species Interactions ◽  
Stress Gradient ◽  
Species Interaction ◽  
Positive Interactions ◽  
Costs And Benefits ◽  
Strong Basis ◽  
Stress Gradients ◽  
High Resource

Understanding the variation in species interactions along environmental stress gradients is crucial for making robust ecological predictions about community responses to changing environmental conditions. The facilitation–competition framework has provided a strong basis for predictions (e.g. the stress-gradient hypothesis, SGH), yet the mechanisms behind patterns in animal interactions on stress gradients are poorly explored in particular for mobile animals. Here, we proposed a conceptual framework modelling changes in facilitation costs and benefits along stress gradients and experimentally tested this framework by measuring fitness outcomes of benefactor–beneficiary interactions across resource quality levels. Three arthropod consumer models from a broad array of environmental conditions were used including aquatic detritivores, potato moths and rainforest carrion beetles. We detected a shift to more positive interactions at increasing levels of stress thereby supporting the application of the SGH to mobile animals. While most benefactors paid no significant cost of facilitation, an increase in potato moth beneficiary's growth at high resource stress triggered costs for benefactors. This study is the first to experimentally show that both costs and benefits function simultaneously on stress gradients for animals. The proposed conceptual framework could guide future studies examining species interaction outcomes for both animals and plants in an increasingly stressed world.

scholarly journals Comparative study of some bioactive compounds and their antioxidant activity of some berry types

10.5219/1132 ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 515-523 ◽  
Author(s):  
Amina Aly ◽  
Rabab Maraei ◽  
Omneya Abou El-Leel
Keyword(s):  
Antioxidant Activity ◽  
Free Radicals ◽  
Chemical Composition ◽  
Phenolic Compounds ◽  
Bioactive Compounds ◽  
Environmental Conditions ◽  
The Body ◽  
Harvest Time ◽  
Berry Fruits ◽  
Red Currant

Berries are wealthy in bioactive compounds like phenolic compounds and flavonoids that are deemed antioxidants and are great important to health. This research was performed to examine, recognize and compare bioactive compounds in certain types of berries and their antioxidant activity. The data show that blue berry, black berry and Egyptian black mulberry contain the highest content of most bioactive compounds such as phenolic compounds, flavonoids and tannins, while long mulberry and red currant berry have the lowest content for most of these compounds. They therefore, contain the highest value of antioxidant activity. The chemical composition of the berries varies depending on cultivar, variety, location of growth, environmental conditions and harvest time, as well as post-harvest treatments therefore the composition differed from berry fruit to another. Thus, berry fruits are very useful in nutrition to protect the body from many diseases because of its containment of these compounds, which act as free radicals scavenger that harm the body and thus rid the body of many harmful toxins.

scholarly journals Peat decomposition – shaping factors, significance in environmental studies and methods of determination; a literature review

Geologos ◽  
2016 ◽  
Vol 22 (1) ◽  
pp. 61-69 ◽  
Author(s):  
Danuta Drzymulska
Keyword(s):  
Chemical Composition ◽  
Literature Review ◽  
Ground Water ◽  
Environmental Conditions ◽  
Meteoric Water ◽  
Climatic Conditions ◽  
Review Of Literature ◽  
Forming Process ◽  
Physical And Chemical

Abstract A review of literature data on the degree of peat decomposition – an important parameter that yields data on environmental conditions during the peat-forming process, i.e., humidity of the mire surface, is presented. A decrease in the rate of peat decomposition indicates a rise of the ground water table. In the case of bogs, which receive exclusively atmospheric (meteoric) water, data on changes in the wetness of past mire surfaces could even be treated as data on past climates. Different factors shaping the process of peat decomposition are also discussed, such as humidity of the substratum and climatic conditions, as well as the chemical composition of peat-forming plants. Methods for the determination of the degree of peat decomposition are also outlined, maintaining the division into field and laboratory analyses. Among the latter are methods based on physical and chemical features of peat and microscopic methods. Comparisons of results obtained by different methods can occasionally be difficult, which may be ascribed to different experience of researchers or the chemically undefined nature of many analyses of humification.

scholarly journals Why economics matters for understanding the effects of climate change on fisheries

2012 ◽  
Vol 69 (7) ◽  
pp. 1160-1167 ◽  
Author(s):  
Alan C. Haynie ◽  
Lisa Pfeiffer
Keyword(s):  
Climate Change ◽  
Conceptual Framework ◽  
Environmental Conditions ◽  
Economic Factors ◽  
Marine Science ◽  
Biological Factors ◽  
Climate Effects ◽  
Economic Mechanisms

Abstract Haynie, A. C., and Pfeiffer, L. 2012. Why economics matters for understanding the effects of climate change on fisheries. – ICES Journal of Marine Science, 69: . Research attempting to predict the effect of climate change on fisheries often neglects to consider how harvesters respond to changing economic, institutional, and environmental conditions, which leads to the overly simplistic prediction of “fisheries follow fish”. However, climate effects on fisheries can be complex because they arise through physical, biological, and economic mechanisms that interact or may not be well understood. Although most researchers find it obvious to include physical and biological factors in predicting the effects of climate change on fisheries, the behaviour of fish harvesters also matters for these predictions. A general but succinct conceptual framework for investigating the effects of climate change on fisheries that incorporates the biological and economic factors that determine how fisheries operate is presented. The use of this framework will result in more complete, reliable, and relevant investigations of the effects of climate change on fisheries. The uncertainty surrounding long-term projections, however, is inherent in the complexity of the system.

How Individualized Niches Arise: Mechanisms of Niche Construction, Niche Choice, and Niche Conformance

2021 ◽  
Author(s):  
Rose Trappes ◽  
Behzad Nematipour ◽  
Marie I. Kaiser ◽  
Ulrich Krohs ◽  
Koen J. van Benthem ◽  
...  
Keyword(s):  
Individual Differences ◽  
Conceptual Framework ◽  
Environmental Conditions ◽  
Niche Construction ◽  
Modern Synthesis ◽  
Evolutionary Synthesis ◽  
Narrow Sense ◽  
Extended Evolutionary Synthesis ◽  
Individual Level

The debate between the extended evolutionary synthesis (EES) and the modern synthesis (MS) partly relies on different interpretations of niche construction. We dissect the umbrella term of niche construction into three separate mechanisms: niche construction (taken in a narrow sense), in which individuals make changes to the environment; niche choice, in which individuals select an environment; and niche conformance, in which individuals change their phenotypes. Each of these individual-level mechanisms affects an individual’s phenotype-environment match, its fitness, and its individualized niche, defined in terms of the environmental conditions under which an individual can survive and reproduce. Our conceptual framework distinguishes several ways in which individuals alter the selective regimes that they and other organisms experience. It also places clear emphasis on individual differences and construes niche construction and other processes as evolved mechanisms. We therefore argue that our framework helps to resolve the tensions between EES and MS.

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