My Science School

The Cambrian explosion or Cambrian radiation was an event approximately 541 million years ago in the Cambrian period when practically all major animal phyla started appearing in the fossil record. It lasted for about 13 – 25 million years and resulted in the divergence of most modern metazoan phyla. The event was accompanied by major diversifications in other groups of organisms as well.

The rapid appearance of a wide variety of animals - particularly bilaterians - led to the development of radical new ecological interactions such as predation. Consequently, ecosystems became much more complex than those of the Ediacaran. As the number and variety of organisms increased, they occupied a variety of new marine environments and habitats. Cambrian seas teemed with animals of various sizes, shapes, and ecologies; some lived on or in the sea floor (a benthic lifestyle), while others actively swam in the water column (nektonic).

The fundamental ecological structure of modern marine communities was firmly established during the Cambrian. By the end of the Period, some animals had also made the first temporary forays onto land, soon to be followed by plants.

 

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The period is named after Devon, a county in southwestern England, where a controversial argument in the 1830s over the age and structure of the rocks found distributed throughout the county was eventually resolved by the definition of the Devonian period in the geological timescale. 

A fossil creature from the Devonian discovered more recently has been hailed as a vital link between fish and the first vertebrates to walk on land. Found in the Canadian Arctic in 2004, Tiktaalik had a crocodile-like head and strong, bony fins that scientists think it used like legs to move in shallow waters or even on land. The fish showed other characteristics of terrestrial animals, including ribs, a neck, and nostrils on its snout for breathing air.

Plants began spreading beyond the wetlands during the Devonian, with new types developing that could survive on dry land. Toward the end of the Devonian the first forests arose as stemmed plants evolved strong, woody structures capable of supporting raised branches and leaves. Some Devonian trees are known to have grown 100 feet (30 meters) tall. By the end of the period the first ferns, horsetails, and seed plants had also appeared.

 

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Biostratigraphy is the branch of stratigraphy that uses fossils to establish relative ages of rock and correlate successions of sedimentary rocks within and between depositional basins. A biozone is an interval of geologic strata characterised by certain fossil taxa. Such intervals are often defined by the first appearances (range bases), apparent extinctions (range tops/last appearances), or abundances of fossil index species. These key index species should be relatively abundant, short-lived taxa that are easy to recognise and as geographically widespread as possible. Widely used fossil groups include brachiopods, conodonts, dinoflagellate cysts, foraminifera, graptolites, nannofossil, spores and pollen and trilobites. Zonal schemes based on several different fossil groups can be used in parallel, and the zones can be calibrated to the absolute geological timescale using tie points to rocks which have been radio-isotopically dated.

There are several kinds of biostratigraphy. Formal biostratigraphy is concerned with the delineation of biostratigraphic zones, which are bodies of rock defined by the presence of selected nominal taxa (fossil species or groups whose name is attached to the biostratigraphic zone). A special kind of formal biostratigraphy is called biochronostratigraphy, which requires nominal taxa that are short-lived and thus their existence defines well a short interval of geological time. Informal biostratigraphy is concerned with using fossil taxa to help define ancient environments, a type of study called paleoecology (the study of ancient ecology preserved in sedimentary rocks).

 

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Ammonites, which evolved about 416 million years ago, were once the most abundant animals of the ancient seas. These sea creatures first appeared 415 million years ago in the form of a small, straight shelled creature, known as Bacrites. They quickly evolved into a variety of shapes and sizes including some shaped like hairpins. During their evolution the ammonites faced no less than three catastrophic events that would eventually lead to their extinction. The first event occurred during the Permian (250 million years ago), where only 10% survived. These surviving species went on to flourish throughout the Triassic, however at the end of this period (206 million years ago) they faced near extinction, when all but one species survived. This event marked the end of the Triassic and the beginning of the Jurassic, during which time the number of ammonite species grew once more. The final catastrophe occurred at the end of the Cretaceous period when all species were annihilated and the ammonites became extinct. This event apparently coincided with the death of the dinosaurs.

Based on the fossil record, ammonites came in a wide range of sizes and shapes, from smaller than an inch to as large as nine feet wide. Some ammonites had long, straight shells, while others had helix-shaped shells. Most species, however, had coiled shells lined with progressively larger chambers separated by thin walls called septa.

The many chambers of their shells likely helped these cephalopods glide through the planet’s warm, shallow seas. A thin, tubelike structure called a siphuncle pumped air through the interior chambers of the shell, which scientists believe helped provide buoyancy and move ammonites through the water. It’s unclear whether ammonites were very efficient swimmers, though.

Scientists believed that ammonites, like modern cephalopods, had soft body tissue with tentacles attached to their heads for catching prey. Fossil evidence indicates they had sharp, beaklike jaws to snare prey such as plankton, crustaceans, and other ammonites. They were also preyed on by larger reptiles and fish.

 

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Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago, although the exact origin and timing of the evolution of dinosaurs is the subject of active research.

All continents during the Triassic Period were part of a single land mass called Pangaea. This meant that differences between animals or plants found in different areas were minor.

The climate was relatively hot and dry, and much of the land was covered with large deserts. Unlike today, there were no polar ice caps.

It was in this environment that the reptiles known as dinosaurs first evolved. Reptiles tend to flourish in hot climates because their skin is less porous than, for example, mammal skin, so it loses less water in the heat. Reptile kidneys are also better at conserving water.

Toward the end of the Triassic, a series of earthquakes and massive volcanic eruptions caused Pangaea to slowly begin to break into two. This was the birth of the North Atlantic Ocean.

 

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Fluoride is commonly used in dentistry to strengthen enamel, which is the outer layer of your teeth. Fluoride helps to prevent cavities. It’s also added in small amounts to public water supplies in the United States and in many other countries. This process is called water fluoridation.

When bacteria in your mouth break down sugar and carbs, they produce acids that eat away at the minerals in your tooth enamel. This loss of minerals is called demineralization. Weakened tooth enamel leaves your teeth vulnerable to bacteria that cause cavities.

Fluoride helps to remineralize your tooth enamel, which can prevent cavities and reverse early signs of tooth decay.

Fluoride is found in foods and water, and of course fluoridated toothpastes and mouth rinses. Mouth rinses containing fluoride in lower strengths are available over-the-counter. Stronger concentrations in liquid or table form need a doctor’s prescription.

A dentist can also apply fluoride to the teeth as a gel, foam or varnish. These treatments contain a much higher level of fluoride than the amount found in toothpastes and mouth rinses. Varnishes are painted on the teeth; foams are put into a mouth guard, which is applied to the teeth for 1 to 4 minutes; gels can be painted on or applied through a mouth guard.

 

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For the past century, plant virology and the American Phytopathological Society have a deeply intertwined history. As the Society emerged as a distinct entity in the first decade of the 20th century, viruses were also making their mark as newly described and discovered agents of disease. Interestingly, Tobacco mosaic virus (TMV) and its economic hosts in the Solanaceae, such as tobacco and tomato, also find their origins in the Americas.

What follows is a brief review of the origins of our understanding of “the nature of the virus,” deciphering the basis of host-pathogen interaction, and vignettes of the early TMV workers who developed many of the tools and techniques that have become part of the definition of what it is “to be” a virologist or “to do” virology. As plant molecular virology has its origins in the early 20th century, first from the early descriptive work of viruses diseases (1900-1935), followed by the biochemical, the genetics, and biophysical work (1935-1960), the molecular biology (1960-1980), and our current era of transgenic technology, functional genetics of plant viruses, and using viruses as molecular tools, it is useful to develop a contextual understanding of how we came to work with TMV.

Like other plant pathogenic viruses, TMV has a very wide host range and has different effects depending on the host being infected. Tobacco mosaic virus has been known to cause a production loss for flue cured tobacco of up to two percent in North Carolina. It is known to infect members of nine plant families, and at least 125 individual species, including tobacco, tomato, pepper (all members of the useful Solanaceae), cucumbers, a number of ornamental flowers, and beans including Phaseolus vulgaris and Vigna unguiculata. There are many different strains. The first symptom of this virus disease is a light green coloration between the veins of young leaves. This is followed quickly by the development of a "mosaic" or mottled pattern of light and dark green areas in the leaves. Rugosity may also be seen where the infected plant leaves display small localized random wrinkles. These symptoms develop quickly and are more pronounced on younger leaves. Its infection does not result in plant death, but if infection occurs early in the season, plants are stunted. Lower leaves are subjected to "mosaic burn" especially during periods of hot and dry weather. In these cases, large dead areas develop in the leaves. This constitutes one of the most destructive phases of Tobacco mosaic virus infection. Infected leaves may be crinkled, puckered, or elongated. However, if TMV infects crops like grape and apple, it is almost symptomless.

 

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Wendell M. Stanley was awarded the 1946 Nobel Prize in Chemistry with John Howard Northrop and James Batcheller Sumner. One-half of the prize was awarded to Sumner for "his discovery that enzymes can be crystallized," and the other half was awarded jointly to Northrop and Stanley for "their preparation of enzymes and virus proteins in a pure form." By isolating and crystallizing tobacco mosaic virus (TMV), Stanley demonstrated that viruses blurred the lines between the living organisms studied by biologists and the nonliving molecules studied by chemists.

Trained as a chemist, Stanley approached TMV from a different perspective than that of the microbiologists. He brought a new set of biochemical techniques for crystallization, recently developed by Sumner and modified by Northrop, to the field of virology. Stanley and Northrop were colleagues at the Department of Plant and Animal Pathology, an extension of the Rockefeller Institute for Medical Research in Princeton. With Northrop's encouragement and support, Stanley modeled his TMV work on Northrop's studies of enzymes. Having crystallized the enzyme pepsin in 1929, Northrop demonstrated the following year that it was a pure protein. Five years later, Stanley crystallized TMV and suggested that it, too, was a pure protein. By 1937, however, he recognized that TMV crystals were actually nucleoproteins. Furthermore, Stanley demonstrated that these nucleoproteins, apparently lifeless in crystallized form, sprang back to life and multiplied when dissolved and reintroduced into tobacco. This was a revolutionary discovery, for it challenged the widely held belief that diseases were transmitted only by living organisms.

 

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The earliest known case of infection with HIV-1 in a human was detected in a blood sample collected in 1959 from a man in Kinshasa, Democratic Republic of the Congo. (How he became infected is not known.) Genetic analysis of this blood sample suggested that HIV-1 may have stemmed from a single virus in the late 1940s or early 1950s.

HIV progressively destroys certain types of white blood cells called CD4+ lymphocytes. Lymphocytes help defend the body against foreign cells, infectious organisms, and cancer. Thus, when HIV destroys CD4+ lymphocytes, people become susceptible to attack by many other infectious organisms. Many of the complications of HIV infection, including death, usually result from these other infections and not from HIV infection directly.

HIV-1 originated in Central Africa during the first half of the 20th century when a closely related chimpanzee virus first infected people. The global spread of HIV-1 began in the late 1970s, and AIDS was first recognized in 1981.

In 2016, about 36.7 million people, including 2.1 million children under age 15, were living with HIV infection worldwide. There were 1 million AIDS-related deaths, and 1.8 million people were newly infected.

Most (95%) new infections occur in the developing world. Almost 70% of new HIV infections occur in sub-Saharan Africa, with more than half occurring in women and 1 in 10 occurring in children under 15 years old. However, in many sub-Saharan African countries, the number of new HIV infections has greatly decreased, partly because of international efforts to provide treatment and strategies for prevention.

 

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Romulus Earl Whitaker (born 23 May 1943) is an Indian herpetologist, wildlife conservationist, and founder of the Madras Snake Park, the Andaman and Nicobar Environment Trust (ANET), and the Madras Crocodile Bank Trust. In 2008, Whitaker was selected as an associate laureate in the 2008 Rolex Awards for Enterprise for his efforts to create a network of rainforest research stations throughout India. In 2005, he was a winner of a Whitley Award for outstanding leadership in nature conservation. He used this award to found the Agumbe Rainforest Research Station in Karnataka, for the study of king cobras and their habitat.

He was producer of the 1996, 53-minute, Super 16-mm wildlife documentary, The King and I, made for the National Geographic Channel Explorer program. This film on the natural history of the king cobra, the largest venomous snake in the world, received the Emmy Award for Outstanding News and Documentary Program Achievement, 1998. It also received Best Photography Award, Progetto Natura 8th Stambecco d'Oro Nature Film Festival, Turin, 1997; it was nominated for Best Cinematography, Jackson Hole Wildlife Film Festival 1997; Emmy Nomination for Outstanding Individual Achievement in a Craft-Cinematographers and News and Documentary, 1998, and Best Animal Behaviour, Wildscreen Film Festival 1998.

In February 2007, he was the subject of a critically acclaimed documentary produced by Icon Films and WNET (and broadcast as Supersize Crocs on PBS's Nature series) on oversized crocodiles, which was filmed in India, Ethiopia, and Australia.

In January 2009, Whitaker was in another Nature documentary on real-life reptiles, such as Komodo dragons and dracos that inspired tales of dragons.

In February 2011, BBC Natural World followed Whitaker during his ongoing research into the causes and prevention of snake bites in India.

He has authored several scientific articles and popular books on reptiles, especially on snakes, including the comprehensive field guide, titled Snakes of India - The Field Guide in 2004 on the snakes of India. 

In 2018, he received the Padma Shri, the fourth-highest civilian awards in India for distinguish services in wildlife conservation.

 

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Antibodies that specifically react with self-antigens are called autoantibodies. These antibodies are generated as a result of the loss of tolerance response against self-antigens and can be pathogenic.

Autoantibodies are generated as a result of disrupted central and peripheral tolerance systems, which eventually lead to maturation and differentiation of autoantibody-generating B lymphocytes into autoantibody-releasing plasma cells.

B lymphocytes that produce high-affinity autoantibodies to self-antigen are either eliminated or functionally inactivated, whereas B lymphocytes that produce low-affinity autoantibodies escape the selection process and continue the maturation process.

Natural autoantibodies are primarily generated from (CD5+) B-1 lymphocytes, which are the most abundant B cells in the neonatal repertoire, and non-circulating mature B lymphocytes (marginal zone B lymphocytes). B-1 lymphocytes with an effective antigen-presenting ability can play a crucial role in generating pathogenic autoantibodies in various autoinflammatory diseases.

By binding self-antigens non-specifically and with low affinity, natural autoantibodies can prevent highly autoreactive clones from reacting strongly with self-antigen. This way natural autoantibodies can maintain immune system homeostasis.

 

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A rogue planet is a planet not orbiting a star and thus not being part of a solar system. However, such planets might support life due to geologic activities. The Founders' homeworld in the Omarion Nebula was such a planet, as was Dakala and Trelane's planet of Gothos. (ENT: "Rogue Planet"; DS9: "The Search, Part I"; TOS: "The Squire of Gothos").

Rogue planets do actually exist in the universe. A rogue planet is an object which has equivalent mass to a planet and is not gravitationally bound to any star, and that therefore moves through space as an independent object. Several astronomers claim to have detected such objects (for example, Cha 110913-773444), but those detections remain unconfirmed.

Astronomers have used the Herschel Space Observatory and the Very Large Telescope to observe a very young free-floating planetary-mass object, OTS 44, and demonstrate that the processes characterizing the canonical star-like mode of formation apply to isolated objects down to a few Jupiter masses. Herschel far-infrared observations have shown that OTS 44 is surrounded by a disk of at least 10 Earth masses and thus could eventually form a mini planetary system. Spectroscopic observations of OTS 44 with the SINFONI spectrograph at the Very Large Telescope have revealed that the disk is actively accreting matter, similarly to the disks of young stars. In December 2013, a candidate exomoon of a rogue planet was announced.

In October 2020, OGLE-2016-BLG-1928, an Earth-mass rogue planet, was discovered in the Milky Way.

 

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You must have learnt quite a bit about solar panels in school. An electrical device that converts the energy of light directly into electricity, solar cells or photovoltaic cells tap solar energy. As the energy is produced from a renewable source, our sun, they offer huge potential in helping us move away from energy generated by burning fossil fuels (non-renewable sources)

Given the important role solar cells can play as an energy source, there is plenty of research on to figure out if we can make the process more efficient. Among these are research that aim at increasing the light captured, as it directly influences the energy produced

Design innovation

An innovation suggested by a team of scientists late in 2020 stands to more than double the light that can be captured by solar cells when compared to conventional solar cells. The team, comprising scientists from the U.K., Portugal and Brazil, discovered that etching a simple pattern could lead to this considerable gain.

According to their study, a shallow pattern of grating lines in a chequerboard design on solar cells can increase the current generated by as much as 125%.

Chequerboard pattern

In their attempt to try and trap more sunlight, the researchers experimented with this design along with other designs (vertical grating lines, crossed lines, etc.) and a conventional plain solar cell. Results showed that the chequerboard pattern with random rotations of the repeating units far outperformed the other competing cells and the conventionally used plain one as well.

While the results might not be as impressive when implemented in the real world with the fabrication measures, the change could well lead to positive impact in the design of new solar cells as a whole. Only time and more experiments can tell us if the chequerboard design does yield the results that we yearn for.

 

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The scientific community was understandably shocked in the late 1970s by the discovery of an entirely new group of organisms -- the Archaea. Dr. Carl Woese and his colleagues at the University of Illinois were studying relationships among the prokaryotes using DNA sequences, and found that there were two distinctly different groups. Those "bacteria" that lived at high temperatures or produced methane clustered together as a group well away from the usual bacteria and the eukaryotes. Because of this vast difference in genetic makeup, Woese proposed that life be divided into three domains: Eukaryota, Eubacteria, and Archaebacteria. He later decided that the term Archaebacteria was a misnomer, and shortened it to Archaea. The three domains are shown in the illustration above at right, which illustrates also that each group is very different from the others.

Archaeans include inhabitants of some of the most extreme environments on the planet. Some live near rift vents in the deep sea at temperatures well over 100 degrees Centigrade. Others live in hot springs (such as the ones pictured above), or in extremely alkaline or acid waters. They have been found thriving inside the digestive tracts of cows, termites, and marine life where they produce methane. They live in the anoxic muds of marshes and at the bottom of the ocean, and even thrive in petroleum deposits deep underground.

Archaeans may be the only organisms that can live in extreme habitats such as thermal vents or hypersaline water. They may be extremely abundant in environments that are hostile to all other life forms. However, archaeans are not restricted to extreme environments; new research is showing that archaeans are also quite abundant in the plankton of the open sea. Much is still to be learned about these microbes, but it is clear that the Archaea is a remarkably diverse and successful clade of organisms.

 

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Essentially, Monera is a biological kingdom that is made up of prokaryotes (particularly bacteria). As such, it's composed of single-celled organisms that lack a true nucleus.

Based on previous classifications, kingdom Monera includes organisms known as Archaea (Archaebacteria) in addition to blue-green algae and Schizopyta (bacteria). However, further studies identified unique characteristics of Archaea that allowed them to be separated and identified as a distinct kingdom. 

They are typically unicellular organisms (but one group is mycelial). The genetic material in these organisms is the naked circular DNA. A nuclear envelope is absent. Both, ribosomes and simple chromatophores, are the only subcellular organelles in the cytoplasm.

The predominant mode of nutrition is absorptive but some groups are photosynthetic (holophytic) and chemosynthetic. The organisms are non-motile or move by the beating of simple flagella or by gliding.

 

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