Life

Most of these are synthesized by the ribosomes through an enzyme-catalyzed process called protein biosynthesis. A sequence of amino acids is assembled and joined together based upon gene expression of the cell's nucleic acid. Cells reproduce through a process of cell division in which the parent cell divides into two or more daughter cells. For prokaryotes, cell division occurs through a process of fission in which the DNA is replicated, then the two copies are attached to parts of the cell membrane. In eukaryotes , a more complex process of mitosis is followed.

However, the end result is the same; the resulting cell copies are identical to each other and to the original cell except for mutations , and both are capable of further division following an interphase period. Multicellular organisms may have first evolved through the formation of colonies of identical cells.

These cells can form group organisms through cell adhesion. The individual members of a colony are capable of surviving on their own, whereas the members of a true multi-cellular organism have developed specializations, making them dependent on the remainder of the organism for survival. Such organisms are formed clonally or from a single germ cell that is capable of forming the various specialized cells that form the adult organism.

This specialization allows multicellular organisms to exploit resources more efficiently than single cells. Cells have evolved methods to perceive and respond to their microenvironment, thereby enhancing their adaptability. Cell signaling coordinates cellular activities, and hence governs the basic functions of multicellular organisms.

Signaling between cells can occur through direct cell contact using juxtacrine signalling , or indirectly through the exchange of agents as in the endocrine system. In more complex organisms, coordination of activities can occur through a dedicated nervous system. Though life is confirmed only on Earth, many think that extraterrestrial life is not only plausible, but probable or inevitable. Other locations within the Solar System that may host microbial life include the subsurface of Mars , the upper atmosphere of Venus , [] and subsurface oceans on some of the moons of the giant planets.

The inner and outer radii of this zone vary with the luminosity of the star, as does the time interval during which the zone survives. Stars more massive than the Sun have a larger habitable zone, but remain on the Sun-like "main sequence" of stellar evolution for a shorter time interval. Small red dwarfs have the opposite problem, with a smaller habitable zone that is subject to higher levels of magnetic activity and the effects of tidal locking from close orbits.

Hence, stars in the intermediate mass range such as the Sun may have a greater likelihood for Earth-like life to develop. Stars in regions with a greater abundance of heavier elements that can form planets, in combination with a low rate of potentially habitat -damaging supernova events, are predicted to have a higher probability of hosting planets with complex life. As a result, the number of civilizations in the galaxy can be estimated as low as 9. Artificial life is the simulation of any aspect of life, as through computers, robotics , or biochemistry.

Scientists study the logic of living systems by creating artificial environments—seeking to understand the complex information processing that defines such systems. Synthetic biology is a new area of biotechnology that combines science and biological engineering. The common goal is the design and construction of new biological functions and systems not found in nature. Synthetic biology includes the broad redefinition and expansion of biotechnology , with the ultimate goals of being able to design and build engineered biological systems that process information, manipulate chemicals, fabricate materials and structures, produce energy, provide food, and maintain and enhance human health and the environment.

Death is the permanent termination of all vital functions or life processes in an organism or cell. After death, the remains of an organism re-enter the biogeochemical cycle. Organisms may be consumed by a predator or a scavenger and leftover organic material may then be further decomposed by detritivores , organisms that recycle detritus , returning it to the environment for reuse in the food chain.

One of the challenges in defining death is in distinguishing it from life. Death would seem to refer to either the moment life ends, or when the state that follows life begins. This is problematic, however, because there is little consensus over how to define life. The nature of death has for millennia been a central concern of the world's religious traditions and of philosophical inquiry. Many religions maintain faith in either a kind of afterlife or reincarnation for the soul , or resurrection of the body at a later date.

Extinction is the process by which a group of taxa or species dies out, reducing biodiversity. Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively after a period of apparent absence. Species become extinct when they are no longer able to survive in changing habitat or against superior competition. Fossils are the preserved remains or traces of animals, plants, and other organisms from the remote past.

The totality of fossils, both discovered and undiscovered, and their placement in fossil-containing rock formations and sedimentary layers strata is known as the fossil record. A preserved specimen is called a fossil if it is older than the arbitrary date of 10, years ago. From Wikipedia, the free encyclopedia. For other uses, see Life disambiguation. For "Life" in the personal sense, see Personal life and Everyday life. For technical reasons , "Life 9" redirects here.

Plant growth in the Hoh Rainforest. Herds of zebra and impala gathering on the Maasai Mara plain. Human timeline and Nature timeline. This section needs expansion. You can help by adding to it. Extraterrestrial life , Astrobiology , and Astroecology. Artificial life and Synthetic biology. Biology , the study of life Astrobiology Biosignature Evolutionary history of life Lists of organisms by population Phylogenetics Viable System Theory. Therefore, this classification may be paraphyletic because cellular life might have evolved from non-cellular life, or polyphyletic because the most recent common ancestor might not be included.

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Life - Wikiquote

Speculations about the age of the earth and primitive mantle characteristics". Earth and Planetary Science Letters. Archived from the original on 20 May Retrieved 13 April Retrieved 9 October Archived PDF from the original on 6 November Retrieved 20 October Early edition, published online before print. Archived from the original on 14 November Retrieved 14 November Archived from the original on 1 January Retrieved 7 July Fossils at a Glance 2nd ed.

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Handbook for the Deep Ecologist: National Academy of Sciences. Archived from the original on 10 May Retrieved 3 June Current Opinion in Chemical Biology. Archived from the original on 5 January Retrieved 15 November Friedrich Miescher and the early years of nucleic acid research". This work caught the eye of artist Nicola Greene, who selected her work to be included in the Discerning Eye Exhibition at the Mall Galleries in Central London in The youngest artist represented in that group, she created the series Dwelling: His interest in photography began during his time as a student at Eton and, though he briefly studied architecture at Cambridge, it continued as he left school to set up a photo studio in London, where he became known for throwing wild parties and hosting a revolving door of celebrities.

In fact, after the couple divorced 18 years later, he continued to photograph the royal family. His photography appeared in the pages of Vogue , Vanity Fair and Tatler, and he worked for the Sunday Times for nearly 30 years. In , he received a major retrospective of his work at the National Portrait Gallery and over of his images now live in the permanent collection. As a staff photographer, he covered everything from war zones to royalty to Muhammad Ali. A member of the Canadian News Hall of Fame , he was known for always getting his shot no matter what the circumstances and for putting his subjects at ease.

But, according to World Press Photo , though the photo was commissioned by The Globe and Mail, it was never actually run by the paper. Because the editors worried that readers would be offended by the image of a dog urinating, it was never published in the paper — even when they reported on it winning a World Press award. She was 97 years old. Although not formally trained, she would go on to shoot for magazines such as Vogue and Town and Country and photographed many famous faces of the day, including actor Vivien Leigh and model Suzy Parker.

She received her degree in and soon after joined the art department at Vogue , after turning down a position at the Museum of Modern Art. Although hired as an assistant in the art department there, she also became an assistant to Toni Frissell, the leading female fashion photographer of the time. Her early interest in watercolor is also evident in the soft atmospheric lighting and palette of her work. Known for his brilliant, saturated color images, his work blurred the line between art and commercial photography.

His experiments with color began when he was a teenager in Rochester, N. His first major assignment came in where he traveled to Africa for Airstream and National Geographic. One hundred of these images can be seen in the book Color of Jazz. In one gimmick, a horse that supposedly possessed clairvoyant powers even composed a headline for a LIFE story about herself. She was clairvoyant, not creative: Mary Breckenridge who runs Frontier Nursing Service, petting her horse. Leslie Country, Kentucky, Inside the Navajo Nation in ","excerpt": The Navajo Nation, which comprised about 61, members at the time and was the fastest-growing Native American group in the nation, was at a moment of crisis.

How can nations which differ from each other in appearance and language and culture live peaceably together? But in the consequences could no longer be denied. Though those policy-makers thought they saving the land from overgrazing, Wilkins says that in fact later research shows that the Navajo livestock were not a primary cause of the problems. How can two very different nations live peaceably together? Seated close to the evening fire, old man Gray Mountain, 91, tells his small grandchildren legends about the early days of the Navajo people.

Inside the Navajo Nation in ","url": Toward sunddown the Yellowsalts finish up their outdoor chores and start the fire for evening meal. In background is Navajo Mountain. One of the people's sacred peaks. Yellowsalt's son has his hair brushed by wife. Nowadays many young Navajos wear their hair short. Baking bread, a woman kneels by the fire while loaf cooks on crude metal grill. This native bread is a major item of Navajo diet.

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Game of marbles, one popular part of white man's culture, is explained by small boy at center to brother and sister. This boy goes to school and learned the game there. His brother has to stay home to help with the sheepherding. Navajo schoolchildren get a lesson in nose blowing from white teacher. See the Navajo Nation in ","description": Fashion Takes a Trip,' show how the social change of the s influenced American style","format": Nearly every aspect of that revolutionary decade, from the civil-rights movement to the space race, was somehow reflected in the clothing worn by American women.

Fashion Takes a Trip , which is being released in coordination with a show of the same name at the Museum of the City of New York opening Wednesday , takes a look at the influences behind and lasting influence of American fashion in the years between and High fashion, after all, was synonymous with France. By , as John and Jacqueline Kennedy — whose personal style was often drawn from French influences — floated into the White House with an aura of American youth, the idea of truly American fashion was not so far-fetched.

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Though Jackie Kennedy broke new ground for American fashion, she made way for a series of looser and more revolutionary looks than she herself presented. Art and youth movements made themselves known in the fashion world. Black models and African-inflected clothing inspired and reflected the pride of the civil-rights movement. Feminism was embodied first in miniskirts, which defied the model femininity of the s, and then with clothing designed for women in careers.

Photograph by Frederick Kelly. Published in Harper's Bazaar, September Fashion Takes a Trip,' show how the social change of the s influenced American style. On that day, thousands of people became citizens","format": But first Veterans Day that was dedicated to veterans of all wars also happened to honor a different group of Americans.

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Eisenhower issued the first Veterans Day proclamation and the new holiday officially replaced Armistice Day — a whopping 50, men and women from coast to coast were sworn in as new U. Missouri in Bremerton, Wash. Attorney General Herbert Brownell Jr. Immigration function in New York would be moved to a different building, off the island, on Nov. In mass induction of 9, new citizens, men and women at New York's Polo Grounds raise their right hands to take oath of allegiance.

On that day, thousands of people became citizens. A man with four children, waiting. And that man, he was fairly sure, appeared to be his own grandfather. Greco found the earliest known photographs of his family by accident. And that man, he was fairly sure, appeared to be his own grandfather, Raffaele Greco. Because the image had not been published in the magazine, the family had not known about its existence until that moment.

In the years after World War II, the family was well-off for the time and place, but not by American standards. The couple decided that they ought to make the move to her homeland around , though the precise reasons for that timing have been lost to family memory. The other three children in the photo are Allen, Vivian and Anna Marie, ages 5, 3 and nearly 2. In an environment of tense McCarthy-era Cold War fear, the act was billed as a way to keep the nation safe from the insidious influence of communism. The way it was framed, however, was a problem — so much so that the law passed despite a veto by President Truman, who argued that the act would help communists by proving that the United States was not the free nation it claimed to be.

In Italy, every school was a Fascist school. It would bar all repentant Communists, interfere with trade with Yugoslavia, exclude many of the 55, German refugees from East Europe, whose admission Congress had just authorized last June. To deal with the bottleneck before it became a crisis, the State Department soon cancelled all U. Though its constitutionality was at first upheld when challenged and select portions of the law still stand, many parts of it were struck down over the next few decades.

According to news reports from the time, the Saturnia passengers who were detained comprised the largest group held under the law at that point. The original version of a photo caption in this gallery misidentified the vessel the passengers were on immediately prior to processing at Ellis Island. It was a ferry, not the Saturnia. The Greco family is at right. The Greco family can be seen at right.

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The show also features images of modern-day adaptations of his signature nonviolent demonstrations, showcasing photos of the 50th anniversary commemoration of the march in Selma, Ala. Even as photography helped to make change on a national level, the people who appeared in those images could be harmed on an individual level as a result of opening up their lives to that exposure.

But I think from that … people saw how people are being treated. So from that sense, it did what it was supposed to do. Civil Rights Photography runs through May 27, High Museum of Art, Atlanta, purchase with funds from the H. High Museum of Art, Atlanta, purchase, Fernandez American, born , Memorial to Dr. Fernandez, courtesy of High Museum of Art","alt": How a Picture Changed a Family's Life","description": He is writing a book about Gordon Parks. Some had left homes in the rural South. Others came from cities like Memphis, Chicago and Los Angeles.

Most were African Americans, but Latinos, white, and members of half a dozen Native American nations were on hand as well. Virtually all of them were poor. Indeed, King believed that the nation was in crisis. Like King, she sensed that America faced an existential crisis. In a recent interview, she told me that his assassination in April , only weeks before the PPC was scheduled to arrive in Washington, left her devastated and searching for a way to respond.

A chance encounter with a campaign organizer in Central Park seemed to supply the answer. Resurrection City, , an exhibition that opens at the Steven Kasher Gallery on Thursday, and her new book, Resurrection City, , showcase the photographs that she made as a participant in the PPC. At the time, she was little more than an enthusiastic amateur with a darkroom. She was in love with the art and craft of photography, however, and was especially drawn to the way the photo-essays she saw in LIFE magazine, by photographers such as of W. Eugene Smith, told stories about the quiet heroism of ordinary people.

Photography like this had the potential to change the world, at least in some small way, and Freedman wanted to play her part. By joining the PPC, she committed herself to documenting the campaign that King had called into being. The encampment was a magnet for photographers. Scores came and went, and some made compelling photographs. But of those photographers only Freedman lived in the city, from beginning to end, and her pictures stand out from all the others. Visits by Sidney Poitier and other celebrities, and concerts by the likes of jazz trumpeter Dizzy Gillespie, also provided photographers occasions for making photographs that instantly caught the eye.

It was important, after all, to document the protests and the police. Avoiding most of the easy drama and all of the celebrities, she offers instead portraits of ordinary people — the women, men and children who were the unheralded heroes of the movement. Her refusal to concentrate on protests and charismatic leaders challenges her viewers. She asks her audience to see the dignity and humanity amid the grime, the anger, and the rain.

An article by staff writer John Neary that accompanied the photo-essay contained some of the most insightful reporting on Resurrection City to appear anywhere. He is writing a book on the photographer, writer, and filmmaker Gordon Parks. Page 22 photo by Rowland Scherman. Page 24 photos by Rowland Sherman top , Jill Freedman bottom. Page 27 photo by Jill Freedman top and bottom right , Rowland Scherman center. Page 28 photo by Rowland Scherman. Page 29 photo by Charles Phillips. When he had begun teaching in , he had been even more of a rarity.

It had become an advocacy group that promoted the idea that male and female adults alike should be fully present in the education system, as teachers or at least as parent volunteers. Especially to small girls like Nancy Thweatt, who clings to his bright shirt sleeve. L'Orange talks with Kim Moscato during a coloring project in which children drew pictures of themselves. Before this year none of the first graders had spent the whole day in school. Some need a great deal of attention, and all need the kind of affection L'Orange provides.

He helps Peter Androcopolus print his name. Lori DeWilkens displays her own mysterious powers of concentration. Word games and pantomimes are regular events in Room 7. Bill L'Orange whispers in Clinton Smith's ear the name of an animal the rest of the class is supposed to guess. Steve Mercier quizzes L'Orange during a free session.