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Stromatolites
Stromatolites () or stromatoliths () are layered sedimentary formations (microbialite) that are created mainly by photosynthetic microorganisms such as cyanobacteria, sulfate-reducing bacteria, and Pseudomonadota (formerly proteobacteria). These microorganisms produce adhesive compounds that cement sand and other rocky materials to form mineral "microbial mats". In turn, these mats build up layer by layer, growing gradually over time. A stromatolite may grow to a meter or more. Although they are rare today, fossilized stromatolites provide records of ancient life on Earth. Morphology Stromatolites are layered, biochemical, accretionary structures formed in shallow water by the trapping, binding and cementation of sedimentary grains in biofilms (specifically microbial mats), through the action of certain microbial lifeforms, especially cyanobacteria. They exhibit a variety of forms and structures, or morphologies, including conical, stratiform, domal, columnar, and branching ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stromatolites In Sharkbay
Stromatolites () or stromatoliths () are layered sedimentary formations (microbialite) that are created mainly by photosynthetic microorganisms such as cyanobacteria, sulfate-reducing bacteria, and Pseudomonadota (formerly proteobacteria). These microorganisms produce adhesive compounds that cement sand and other rocky materials to form mineral "microbial mats". In turn, these mats build up layer by layer, growing gradually over time. A stromatolite may grow to a meter or more. Although they are rare today, fossilized stromatolites provide records of ancient life on Earth. Morphology Stromatolites are layered, biochemical, accretionary structures formed in shallow water by the trapping, binding and cementation of sedimentary grains in biofilms (specifically microbial mats), through the action of certain microbial lifeforms, especially cyanobacteria. They exhibit a variety of forms and structures, or morphologies, including conical, stratiform, domal, columnar, and branching ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microbial Mat
A microbial mat is a multi-layered sheet of microorganisms, mainly bacteria and archaea, or bacteria alone. Microbial mats grow at interfaces between different types of material, mostly on submerged or moist surfaces, but a few survive in deserts. A few are found as endosymbionts of animals. Although only a few centimetres thick at most, microbial mats create a wide range of internal chemical environments, and hence generally consist of layers of microorganisms that can feed on or at least tolerate the dominant chemicals at their level and which are usually of closely related species. In moist conditions mats are usually held together by slimy substances secreted by the microorganisms. In many cases some of the bacteria form tangled webs of filaments which make the mat tougher. The best known physical forms are flat mats and stubby pillars called stromatolites, but there are also spherical forms. Microbial mats are the earliest form of life on Earth for which there is good fossi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microbialite
Microbialite is a benthic sedimentary deposit made of carbonate mud (particle diameter < 5 μm) that is formed with the mediation of microbes. The constituent carbonate mud is a type of , or authigenic mud, and therefore it precipitates in situ instead of being transported and deposited. Being formed in situ, a microbialite can be seen as a type of boundstone where reef builders are microbes, and precipitation of carbonate is biotically induced instead of forming tests, shells or skeletons. Microbialites can also be defined as |
Cyanobacteria
Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blue-green algae, although they are not usually scientifically classified as algae. They appear to have originated in a freshwater or terrestrial environment. Sericytochromatia, the proposed name of the paraphyletic and most basal group, is the ancestor of both the non-photosynthetic group Melainabacteria and the photosynthetic cyanobacteria, also called Oxyphotobacteria. Cyanobacteria use photosynthetic pigments, such as carotenoids, phycobilins, and various forms of chlorophyll, which absorb energy from light. Unlike heterotrophic prokaryotes, cyanobacteria have internal membranes. These are flattened sacs called thylakoids where photosynthesis is performed. Phototrophic eukaryotes such as green plants perform photosynthesis in plast ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Porostromate
"Porostromata" is an antiquated form taxon that refers to fossil cyanobacteria. The term porostromate is also used as a descriptor of textures and microstructure of stromatolites and oncolites which contain tubules or other cellular structures. The group was defined by Pia (1927) as containing calcareous algae bearing calcified tubules; these may run parallel to the growth surface as in ''Girvanella'', ''Sphaerocodium'' or perpendicular, as in ''Hedstroemia'', '' Ortonella'', and '' Mitcheldaenia''; however, in 1937 Pia restricted the group to only ''Girvanella'' and ''Sphaerocodium'', placing the other genera in the Codiaceae. In reality it seems that most or all of the species included in "Porostromata" represent fossils of cyanobacteria. Monty (1981) advocated continued use of porostramata in an informal sense to describe a habit and structure of bacterial colonies, rather than in a taxonomic sense. He defined a "porostromate" microstructure as follows:"Porostromate microst ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleoproterozoic Stromatolites Oncoids Franceville
The Paleoproterozoic Era (;, also spelled Palaeoproterozoic), spanning the time period from (2.5–1.6 Ga), is the first of the three sub-divisions (eras) of the Proterozoic Eon. The Paleoproterozoic is also the longest era of the Earth's geological history. It was during this era that the continents first stabilized. Paleontological evidence suggests that the Earth's rotational rate ~1.8 billion years ago equated to 20-hour days, implying a total of ~450 days per year. Atmosphere Before the enormous increase in atmospheric oxygen, almost all existing lifeforms were anaerobic organisms whose metabolism was based on a form of cellular respiration that did not require oxygen. Free oxygen in large amounts is toxic to most anaerobic organisms. Consequently, most died when the atmospheric free oxygen levels soared in an extinction event called the Great Oxidation Event, which brought atmospheric oxygen levels to up to 10% of their current level. The only creatures that survi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Precambrian
The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the Phanerozoic Eon, which is named after Cambria, the Latinised name for Wales, where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth's geologic time. The Precambrian is an informal unit of geologic time, subdivided into three eons ( Hadean, Archean, Proterozoic) of the geologic time scale. It spans from the formation of Earth about 4.6 billion years ago ( Ga) to the beginning of the Cambrian Period, about million years ago ( Ma), when hard-shelled creatures first appeared in abundance. Overview Relatively little is known about the Precambrian, despite it making up roughly seven-eighths of the Earth's history, and what is known has largely been discovered from the 1960s onwards. The Precambrian fossil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spongiostromate
"Spongiostromata" is an antiquated form taxon that refers primarily to fossil cyanobacteria. "Spongiostromate" is also used to describe stromatolites and oncolite Oncolites are sedimentary structures composed of oncoids, which are layered structures formed by cyanobacterial growth. Oncolites are very similar to stromatolites, but, instead of forming columns, they form approximately spherical structures. T ...s that do not preserve clear tubules or other cellular microstructure. Pia (1927) erected the group to contain calcareous algal fossils that contain no visible cellular structure but which he presumed represented cyanobacteria based on comparisons to modern examples. He divided the taxon into two groups: the '' stromatolithi'' and the ''Oncolite, oncolithi''. Monty (1981) abolished the group as taxonomically uninformative but advocated for the use of "spongiostromata" to describe a form and texture of bacterial fossils. He defined a "spongiostromate" texture as follows:"S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cementation (geology)
Cementation involves ions carried in groundwater chemically precipitating to form new crystalline material between sedimentary grains. The new pore-filling minerals forms "bridges" between original sediment grains, thereby binding them together. In this way, ''sand'' becomes sandstone, and ''gravel'' becomes conglomerate or breccia. Cementation occurs as part of the diagenesis or lithification of sediments. Cementation occurs primarily below the water table regardless of sedimentary grain sizes present. Large volumes of pore water must pass through sediment pores for new mineral cements to crystallize and so millions of years are generally required to complete the cementation process. Common mineral cements include calcite, quartz, and silica phases like cristobalite, iron oxides, and clay minerals; other mineral cements also occur. Cementation is continuous in the groundwater zone, so much so that the term "zone of cementation" is sometimes used interchangeably. Cementati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biofilm
A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular polymeric substances (EPSs). The cells within the biofilm produce the EPS components, which are typically a polymeric conglomeration of extracellular polysaccharides, proteins, lipids and DNA. Because they have three-dimensional structure and represent a community lifestyle for microorganisms, they have been metaphorically described as "cities for microbes". Biofilms may form on living or non-living surfaces and can be prevalent in natural, industrial, and hospital settings. They may constitute a microbiome or be a portion of it. The microbial cells growing in a biofilm are physiologically distinct from planktonic cells of the same organism, which, by contrast, are single cells that may float or swim in a liquid medium. Biofilms can form ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biota (ecology)
A biome () is a biogeographical unit consisting of a biological community that has formed in response to the physical environment in which they are found and a shared regional climate. Biomes may span more than one continent. Biome is a broader term than habitat and can comprise a variety of habitats. While a biome can cover large areas, a microbiome is a mix of organisms that coexist in a defined space on a much smaller scale. For example, the human microbiome is the collection of bacteria, viruses, and other microorganisms that are present on or in a human body. A biota is the total collection of organisms of a geographic region or a time period, from local geographic scales and instantaneous temporal scales all the way up to whole-planet and whole-timescale spatiotemporal scales. The biotas of the Earth make up the biosphere. Etymology The term was suggested in 1916 by Clements, originally as a synonym for '' biotic community'' of Möbius (1877). Later, it gained its c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
