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The origin of life on Earth, explained

The origin of life on Earth stands as one of the great mysteries of science. Various answers have been proposed, all of which remain unverified. To find out if we are alone in the galaxy, we will need to better understand what geochemical conditions nurtured the first life forms. What water, chemistry and temperature cycles fostered the chemical reactions that allowed life to emerge on our planet? Because life arose in the largely unknown surface conditions of Earth’s early history, answering these and other questions remains a challenge.

Several seminal experiments in this topic have been conducted at the University of Chicago, including the Miller-Urey experiment that suggested how the building blocks of life could form in a primordial soup.

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• When did life on Earth begin?

Where did life on Earth begin?

What are the ingredients of life on earth, what are the major scientific theories for how life emerged, what is chirality and why is it biologically important, what research are uchicago scientists currently conducting on the origins of life, when did life on earth begin .

Earth is about 4.5 billion years old. Scientists think that by 4.3 billion years ago, Earth may have developed conditions suitable to support life. The oldest known fossils, however, are only 3.7 billion years old. During that 600 million-year window, life may have emerged repeatedly, only to be snuffed out by catastrophic collisions with asteroids and comets.

The details of those early events are not well preserved in Earth’s oldest rocks. Some hints come from the oldest zircons, highly durable minerals that formed in magma. Scientists have found traces of a form of carbon—an important element in living organisms— in one such 4.1 billion-year-old zircon . However, it does not provide enough evidence to prove life’s existence at that early date.

Two possibilities are in volcanically active hydrothermal environments on land and at sea.

Some microorganisms thrive in the scalding, highly acidic hot springs environments like those found today in Iceland, Norway and Yellowstone National Park. The same goes for deep-sea hydrothermal vents. These chimney-like vents form where seawater comes into contact with magma on the ocean floor, resulting in streams of superheated plumes. The microorganisms that live near such plumes have led some scientists to suggest them as the birthplaces of Earth’s first life forms.

Organic molecules may also have formed in certain types of clay minerals that could have offered favorable conditions for protection and preservation. This could have happened on Earth during its early history, or on comets and asteroids that later brought them to Earth in collisions. This would suggest that the same process could have seeded life on planets elsewhere in the universe.

The recipe consists of a steady energy source, organic compounds and water.

Sunlight provides the energy source at the surface, which drives photosynthesis. On the ocean floor, geothermal energy supplies the chemical nutrients that organisms need to live.

Also crucial are the elements important to life . For us, these are carbon, hydrogen, oxygen, nitrogen, and phosphorus. But there are several scientific mysteries about how these elements wound up together on Earth. For example, scientists would not expect a planet that formed so close to the sun to naturally incorporate carbon and nitrogen. These elements become solid only under very cold temperatures, such as exist in the outer solar system, not nearer to the sun where Earth is. Also, carbon, like gold, is rare at the Earth’s surface. That’s because carbon chemically bonds more often with iron than rock. Gold also bonds more often with metal, so most of it ends up in the Earth’s core. So, how did the small amounts found at the surface get there? Could a similar process also have unfolded on other planets?

The last ingredient is water. Water now covers about 70% of Earth’s surface, but how much sat on the surface 4 billion years ago? Like carbon and nitrogen, water is much more likely to become a part of solid objects that formed at a greater distance from the sun. To explain its presence on Earth, one theory proposes that a class of meteorites called carbonaceous chondrites formed far enough from the sun to have served as a water-delivery system.

There are several theories for how life came to be on Earth. These include:

Life emerged from a primordial soup

As a University of Chicago graduate student in 1952, Stanley Miller performed a famous experiment with Harold Urey, a Nobel laureate in chemistry. Their results explored the idea that life formed in a primordial soup.

Miller and Urey injected ammonia, methane and water vapor into an enclosed glass container to simulate what were then believed to be the conditions of Earth’s early atmosphere. Then they passed electrical sparks through the container to simulate lightning. Amino acids, the building blocks of proteins, soon formed. Miller and Urey realized that this process could have paved the way for the molecules needed to produce life.

Scientists now believe that Earth’s early atmosphere had a different chemical makeup from Miller and Urey’s recipe. Even so, the experiment gave rise to a new scientific field called prebiotic or abiotic chemistry, the chemistry that preceded the origin of life. This is the opposite of biogenesis, the idea that only a living organism can beget another living organism.

Seeded by comets or meteors

Some scientists think that some of the molecules important to life may be produced outside the Earth. Instead, they suggest that these ingredients came from meteorites or comets.

“A colleague once told me, ‘It’s a lot easier to build a house out of Legos when they’re falling from the sky,’” said Fred Ciesla, a geophysical sciences professor at UChicago. Ciesla and that colleague, Scott Sandford of the NASA Ames Research Center, published research showing that complex organic compounds were readily produced under conditions that likely prevailed in the early solar system when many meteorites formed.

Meteorites then might have served as the cosmic Mayflowers that transported molecular seeds to Earth. In 1969, the Murchison meteorite that fell in Australia contained dozens of different amino acids—the building blocks of life.

Comets may also have offered a ride to Earth-bound hitchhiking molecules, according to experimental results published in 2001 by a team of researchers from Argonne National Laboratory, the University of California Berkeley, and Lawrence Berkeley National Laboratory. By showing that amino acids could survive a fiery comet collision with Earth, the team bolstered the idea that life’s raw materials came from space.

In 2019, a team of researchers in France and Italy reported finding extraterrestrial organic material preserved in the 3.3 billion-year-old sediments of Barberton, South Africa. The team suggested micrometeorites as the material’s likely source. Further such evidence came in 2022 from samples of asteroid Ryugu returned to Earth by Japan’s Hayabusa2 mission. The count of amino acids found in the Ryugu samples now exceeds 20 different types .

In 1953, UChicago researchers published a landmark paper in the Journal of Biological Chemistry that marked the discovery of the pro-chirality concept , which pervades modern chemistry and biology. The paper described an experiment showing that the chirality of molecules—or “handedness,” much the way the right and left hands differ from one another—drives all life processes. Without chirality, large biological molecules such as proteins would be unable to form structures that could be reproduced.

Today, research on the origin of life at UChicago is expanding. As scientists have been able to find more and more exoplanets—that is, planets around stars elsewhere in the galaxy—the question of what the essential ingredients for life are and how to look for signs of them has heated up.

Nobel laureate Jack Szostak joined the UChicago faculty as University Professor in Chemistry in 2022 and will lead the University’s new interdisciplinary Origins of Life Initiative to coordinate research efforts into the origin of life on Earth. Scientists from several departments of the Physical Sciences Division are joining the initiative, including specialists in chemistry, astronomy, geology and geophysics.

“Right now we are getting truly unprecedented amounts of data coming in: Missions like Hayabusa and OSIRIS-REx are bringing us pieces of asteroids, which helps us understand the conditions that form planets, and NASA’s new JWST telescope is taking astounding data on the solar system and the planets around us ,” said Prof. Ciesla. “I think we’re going to make huge progress on this question.”

Last updated Sept. 19, 2022.

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AP®︎/College Biology

Course: ap®︎/college biology   >   unit 7.

• Earth formation
• Beginnings of life
• Origins of life

Hypotheses about the origins of life

• The RNA origin of life
• Origins of life on Earth

Key points:

• The Earth formed roughly 4.5 ‍   billion years ago, and life probably began between 3.5 ‍   and 3.9 ‍   billion years ago.
• The Oparin-Haldane hypothesis suggests that life arose gradually from inorganic molecules, with “building blocks” like amino acids forming first and then combining to make complex polymers.
• The Miller-Urey experiment provided the first evidence that organic molecules needed for life could be formed from inorganic components.
• Some scientists support the RNA world hypothesis , which suggests that the first life was self-replicating RNA. Others favor the metabolism-first hypothesis , placing metabolic networks before DNA or RNA.
• Simple organic compounds might have come to early Earth on meteorites.

Introduction

When did life appear on earth, the earliest fossil evidence of life, how might life have arisen.

• Simple inorganic molecules could have reacted (with energy from lightning or the sun) to form building blocks like amino acids and nucleotides, which could have accumulated in the oceans, making a "primordial soup." 3 ‍  
• The building blocks could have combined in further reactions, forming larger, more complex molecules (polymers) like proteins and nucleic acids, perhaps in pools at the water's edge.
• The polymers could have assembled into units or structures that were capable of sustaining and replicating themselves. Oparin thought these might have been “colonies” of proteins clustered together to carry out metabolism, while Haldane suggested that macromolecules became enclosed in membranes to make cell-like structures 4 , 5 ‍   .

From inorganic compounds to building blocks

Were miller and urey's results meaningful, from building blocks to polymers, what was the nature of the earliest life, the "genes-first" hypothesis, the "metabolism-first" hypothesis, what might early cells have looked like, another possibility: organic molecules from outer space.

• Miller, Urey, and others showed that simple inorganic molecules could combine to form the organic building blocks required for life as we know it.
• Once formed, these building blocks could have come together to form polymers such as proteins or RNA.
• Many scientists favor the RNA world hypothesis, in which RNA, not DNA, was the first genetic molecule of life on Earth. Other ideas include the pre-RNA world hypothesis and the metabolism-first hypothesis.
• Organic compounds could have been delivered to early Earth by meteorites and other celestial objects.

Works cited:

• Harwood, R. (2012). Patterns in palaeontology: The first 3 billion years of evolution. Palaeontology , 2(11), 1-22. Retrieved from http://www.palaeontologyonline.com/articles/2012/patterns-in-palaeontology-the-first-3-billion-years-of-evolution/ .
• Wacey, D., Kilburn, M. R., Saunders, M., Cliff, J., and Brasier, M. D. (2011). Microfossils of sulphur-metabolizing cells in 3.4-billion-year-old rocks of Western Australia. Nature Geoscience , 4 , 698-702. http://dx.doi.org/10.1038/ngeo1238 .
• Primordial soup. (2016, January 20). Retrieved May 22, 2016 from Wikipedia: https://en.wikipedia.org/wiki/Primordial_soup .
• Gordon-Smith, C. (2003). The Oparin-Haldane hypothesis. In Origin of life: Twentieth century landmarks . Retrieved from http://www.simsoup.info/Origin_Landmarks_Oparin_Haldane.html .
• The Oparin-Haldane hypothesis. (2015, June 14). In Structural biochemistry . Retrieved May 22, 2016 from Wikibooks: https://en.wikibooks.org/wiki/Structural_Biochemistry/The_Oparin-Haldane_Hypothesis .
• Kimball, J. W. (2015, May 17). Miller's experiment. In Kimball's biology pages . Retrieved from http://www.biology-pages.info/A/AbioticSynthesis.html#Miller's_Experiment .
• Earth’s early atmosphere. (Dec 2, 2011). In Astrobiology Magazine . Retrieved from http://www.astrobio.net/topic/solar-system/earth/geology/earths-early-atmosphere/ .
• McCollom, T. M. (2013). Miller-Urey and beyond: What have learned about prebiotic organic synthesis reactions in the past 60 years? Annual Review of Earth and Planetary Sciences , 41_, 207-229. http://dx.doi.org/10.1146/annurev-earth-040610-133457 .
• Powner, M. W., Gerland, B., and Sutherland, J. D. (2009). Synthesis of activated pyrimidine ribonucleotides in prebiotically plausible conditions. Nature , 459 , 239-242. http://dx.doi.org/10.1038/nature08013 .
• Lurquin, P. F. (June 5, 2003). Proteins and metabolism first: The iron-sulfur world. In The origins of life and the universe (pp. 110-111). New York, NY: Columbia University Press.
• Ferris, J. P. (2006). Montmorillonite-catalysed formation of RNA oligomers: The possible role of catalysis in the origins of life. Philos. Trans. R. Soc. Lond. B. Bio.l Sci ., 361 (1474), 1777–1786. http://dx.doi.org/10.1098/rstb.2006.1903 .
• Kimball, J. W. (2015, May 17). Assembling polymers. In Kimball's biology pages . Retrieved from
• Montmorillonite. (2016, 28 March). Retrieved May 22, 2016 from Wikipedia: https://en.wikipedia.org/wiki/Montmorillonite .
• Wilkin, D. and Akre, B. (2016, March 23). First organic molecules - Advanced. In CK-12 biology advanced concepts . Retrieved from http://www.ck12.org/book/CK-12-Biology-Advanced-Concepts/section/10.8/ .
• Hollenstein, M. (2015). DNA catalysis: The chemical repertoire of DNAzymes. Molecules , 20 (11), 20777–20804. http://dx.doi.org/10.3390/molecules201119730 .
• Breaker, R. R. and Joyce, G. F. (2014). The expanding view of RNA and DNA function. Chemistry & biology , 21 (9), 1059–1065. http://dx.doi.org/10.1016/j.chembiol.2014.07.008 .
• Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., and Walter, P. (2002). A pre-RNA world probably predates the RNA world. In Molecular biology of the cell (4th ed.). New York, NY: Garland Science. Retrieved from http://www.ncbi.nlm.nih.gov/books/NBK26876/#_A1124_ .
• Moran, L. A. (2009, May 15). Metabolism first and the origin of life. In Sandwalk: Strolling with a skeptical biochemist . Retrieved from http://www.simsoup.info/Origin_Landmarks_Oparin_Haldane.html .
• Kimball, J. W. (2015, May 17). The first cell? In Kimball's biology pages . Retrieved from http://www.biology-pages.info/A/AbioticSynthesis.html#TheFirstCell?
• Kimball, J. W. (2015, May 17). Molecules from outer space? In Kimball's biology pages . Retrieved from http://www.biology-pages.info/A/AbioticSynthesis.html#Molecules_from_outer_space? .
• Jeffs, W. (2006, November 30). NASA scientists find primordial organic matter in meteorite. In NASA news . Retrieved from http://www.nasa.gov/centers/johnson/news/releases/2006/J06-103.html .

Additional references:

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Understanding Evolution

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From soup to cells: The origin of life

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Studying the origin of life

The origin of life might seem like the ultimate cold case: no one was there to observe it and much of the relevant evidence has been lost in the intervening 3.5 billion years or so. Nonetheless, many separate lines of evidence do shed light on this event, and as biologists continue to investigate these data, they are slowly piecing together a picture of how life originated. Major lines of evidence include DNA, biochemistry, and experiments.

Origins and DNA evidence

Biologists use the DNA sequences of modern organisms to reconstruct the tree of life and to figure out the likely characteristics of the most recent common ancestor of all living things — the “trunk” of the tree of life. In fact, according to some hypotheses, this “most recent common ancestor” may actually be a set of organisms that lived at the same time and were able to swap genes easily. In either case, reconstructing the early branches on the tree of life tells us that this ancestor (or set of ancestors) probably used DNA as its genetic material and performed complex chemical reactions. But what came before it? We know that this last common ancestor must have had ancestors of its own – a long line of forebears forming the root of the tree of life – but to learn about them, we must turn to other lines of evidence.

How did life originate?

Origins and biochemical evidence

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Origin of Life

As per the findings in evolutionary biology, the universe, earth and the variety of life forms are the results of evolution.

What is Evolution?

Evolution mainly deals with the origin of life on earth. The conditions and the forms of life on earth were entirely different from what we see today. Everything evolved from one form to another for a better chance of survival.

Here, let us know in brief about the origin of life on earth.

The Origin of the Universe

The origin of life begins with the origin of the universe. The universe, an old vast and empty space comprising galaxies, originated around 20 billion years ago. There was nothing but blackness filled with gas and dust. The Big Bang Theory is the most accepted theory regarding the origin of the planet earth and the existence of different life forms on it. According to this theory, the universe is a result of a massive explosion which occurred 20 billion years ago. Whether it is a hypothesis or a fact, a new universe was formed. The atmospheric condition after the explosion became more stable. The temperature reduced and gasses like hydrogen and helium formed which led to the formation of galaxies of today.

Later, after 10 billion years, the earth was formed which was covered by water vapour, methane, carbon dioxide, and ammonia. There was no atmosphere but only gases and moisture. The powerful rays of the sun stimulated and hastened evolution . By making and breaking bonds between gas molecules, the earth came out with a new face. After millions of years i.e., once the earth’s atmosphere was stable, the first life on earth came into existence (around 4 million years ago). There began the story of the origin of life on earth.

The Origin of Life

There were lots of hypotheses regarding the origin of life on earth. Certain experts suggested that life came from outer space as spores while another group explained that life came from a non-cellular component such as decaying matters like mud. The latter theory was known as the theory of spontaneous generation, which was discarded later.

In the year 1953, Oparin and Haldane suggested that life originated from non-living organic molecules like proteins and RNA. This was followed by the theory of chemical evolution which suggested that atmospheric conditions of the earth led to the formation of organic molecules from inorganic molecules. Few scientists conducted experiments regarding the same. However, once the first life came into existence, they started to evolve in different ways and forms. This laid a stepping stone to the theory of evolution.

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7 theories on the origin of life

The answer to the origin of life remains unknown, but here are scientists best bets

• An electric spark

Molecules of life met on clay

• Deep-sea vents
• Born from ice
• Understanding DNA
• Simple beginnings
• Life came from space

Additional resources

Bibliography.

The origin of life on Earth began more than 3 billion years ago, evolving from the most basic of microbes into a dazzling array of complexity over time. But how did the first organisms on the only known home to life in the universe develop from the primordial soup?

Science remains undecided and conflicted as to the exact origin of life, also known as abiogenesis. Even the very definition of life is contested and rewritten, with one study published in the J ournal of Biomolecular Structure and Dynamics , suggesting uncovering 123 different published definitions. 

Although science still seems unsure, here are  some of the many different scientific theories on the origin of life on Earth.

It started with an electric spark

Lightning may have provided the spark needed for life to begin.Electric sparks can generate amino acids and sugars from an atmosphere loaded with water, methane, ammonia and hydrogen , as was shown in the famous Miller-Urey experiment  in 1952, according to Scientific American . The experiment's findings  suggested that lightning might have helped create the key building blocks of life on Earth in its early days. Over millions of years, larger and more complex molecules could form. 

Although research since then has revealed the early atmosphere of Earth was actually hydrogen-poor, scientists have suggested that volcanic clouds in the early atmosphere might have held methane, ammonia and hydrogen and been filled with lightning as well, according to the University of California

The first molecules of life might have met on clay, according to an idea elaborated by organic chemist Alexander Graham Cairns-Smith at the University of Glasgow in Scotland. Cairns-Smith proposed in his 1985 controversial book “ Seven Clues to the Origin of Life'' , that clay crystals preserve their structure as they grow and stick together to form areas exposed to different environments and trap other molecules along the way and organise them into patterns much like our genes do now.

– What is the difference between prokaryotic and eukaryotic cells?

– What is biology?

– What are bacteria?

– What is an amoeba?

– Is there water on Mars?

The main role of DNA is to store information on how other molecules should be arranged. Genetic sequences in DNA are essentially instructions on how amino acids should be arranged in proteins. Cairns-Smith suggests that mineral crystals in clay could have arranged organic molecules into organized patterns. After a while, organic molecules took over this job and organized themselves.

Although Cairns-Smith's theory certainly gave scientists food for thought in the 1980s, it has still not been widely accepted by the scientific community.

Life began at deep-sea vents

The deep-sea vent theory suggests that life may have begun at submarine hydrothermal vents spewing elements key to life, such as carbon and hydrogen-, according to the journal Nature Reviews Microbiology .

Hydrothermal vents can be found in the darkest depths of the ocean floors, typically on diverging continental plates, according to the Natural History Museum . These vents erupt fluid which is superheated by the Earth’s core as it passes up through the crust, before being ejected at the vets. During its journey through the crust it collects dissolved gases and minerals, such as carbon and hydrogen. 

Their rocky nooks could then have concentrated these molecules together and provided mineral catalysts for critical reactions. Even now, these vents, rich in chemical and thermal energy, sustain vibrant ecosystems.

Abiogenesis by way of hydrothermal vents continues to be investigated as a plausible cause of life on Earth. In 2019, scientists at University College London , successfully created protocells (non-living structures that help scientists understand the origins of life) under similar hot, alkaline environmental conditions to hydrothermal vents.

Life had a chilly start

Ice might have covered the oceans 3 billion years ago and facilitated the birth of life. "Key organic compounds thought to be important in the origin of life are more stable at lower temperatures,” Jeffrey Bada at the University of California, told New Scientist . At normal temperatures these compounds, such as simple sets of amino acids, are sparsely populated in water, but when frozen become concentrated and facilitate the emergence of life, according to Bada’s work published in the journal I carus .  

Ice also might have protected fragile organic compounds in the water below from ultraviolet light and destruction from cosmic impacts. The cold might have also helped these molecules to survive longer, enabling key reactions to happen. 

The answer lies in understanding DNA formation

Nowadays DNA needs proteins in order to form, and proteins require DNA to form, so how could these have formed without each other? The answer may be RNA , which can store information like DNA, serve as an enzyme like proteins, and help create both DNA and proteins, according to the journal Molecular Biology of the Cell . Later DNA and proteins succeeded this "RNA world," because they are more efficient.

RNA still exists and performs several functions in organisms, including acting as an on-off switch for some genes. The question still remains how RNA got here in the first place. Some scientists think the molecule could have spontaneously arisen on Earth, while others say that was very unlikely to have happened. 

Life had simple beginnings

Instead of developing from complex molecules such as RNA, life might have begun with smaller molecules interacting with each other in cycles of reactions. These might have been contained in simple capsules akin to cell membranes, and over time more complex molecules that performed these reactions better than the smaller ones could have evolved, scenarios dubbed "metabolism-first" models, as opposed to the "gene-first" model of the "RNA world" hypothesis.

Life was brought here from elsewhere in space

Perhaps life did not begin on Earth at all, but was brought here from elsewhere in space, a notion known as panspermia, according to NASA . For instance, rocks regularly get blasted off Mars by cosmic impacts, and a number of Martian meteorites have been found on Earth that some researchers have controversially suggested brought microbes over here, potentially making us all Martians originally. Other scientists have even suggested that life might have hitchhiked on comets from other star systems. However, even if this concept were true, the question of how life began on Earth would then only change to how life began elsewhere in space.

For more information into the theories of life’s origins check out “ The Stairway To Life: An Origin-Of-Life Reality Check ” by Change Laura Tan and “ The Mystery of Life's Origin ” by Charles B. Thaxton, et al. 

Matthew Levy et al, “Prebiotic Synthesis of Adenine and Amino Acids Under Europa-like Conditions”, Icarus, Volume 145, June 2000, https://doi.org/10.1006/icar.2000.6365

William Martin, “Hydrothermal vents and the origin of life”, Nature Reviews Microbiology, Volume 6, September 2008, https://doi.org/10.1038/nrmicro1991  

K. A. Dill and L. Agozzino, “Driving forces in the origins of life”, Open biology, Volume 11, February 2021, ttps://doi.org/10.1098/rsob.200324 

Ben K. D. Pearce et al, “Origin of the RNA world: The fate of nucleobases in warm little ponds”, PNAS, Volume 114, October 2017, https://doi.org/10.1073/pnas.1710339114

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The Origin of the Universe, Earth, and Life

The term "evolution" usually refers to the biological evolution of living things. But the processes by which planets, stars, galaxies, and the universe form and change over time are also types of "evolution." In all of these cases there is change over time, although the processes involved are quite different.

In the late 1920s the American astronomer Edwin Hubble made a very interesting and important discovery. Hubble made observations that he interpreted as showing that distant stars and galaxies are receding from Earth in every direction. Moreover, the velocities of recession increase in proportion with distance, a discovery that has been confirmed by numerous and repeated measurements since Hubble's time. The implication of these findings is that the universe is expanding.

Hubble's hypothesis of an expanding universe leads to certain deductions. One is that the universe was more condensed at a previous time. From this deduction came the suggestion that all the currently observed matter and energy in the universe were initially condensed in a very small and infinitely hot mass. A huge explosion, known as the Big Bang, then sent matter and energy expanding in all directions.

This Big Bang hypothesis led to more testable deductions. One such deduction was that the temperature in deep space today should be several degrees above absolute zero. Observations showed this deduction to be correct. In fact, the Cosmic Microwave Background Explorer (COBE) satellite launched in 1991 confirmed that the background radiation field has exactly the spectrum predicted by a Big Bang origin for the universe.

As the universe expanded, according to current scientific understanding, matter collected into clouds that began to condense and rotate, forming the forerunners of galaxies. Within galaxies, including our own Milky Way galaxy, changes in pressure caused gas and dust to form distinct clouds. In some of these clouds, where there was sufficient mass and the right forces, gravitational attraction caused the cloud to collapse. If the mass of material in the cloud was sufficiently compressed, nuclear reactions began and a star was born.

Some proportion of stars, including our sun, formed in the middle of a flattened spinning disk of material. In the case of our sun, the gas and dust within this disk collided and aggregated into small grains, and the grains formed into larger bodies called planetesimals ("very small planets"), some of which reached diameters of several hundred kilometers. In successive stages these planetesimals coalesced into the nine planets and their numerous satellites. The rocky planets, including Earth, were near the sun, and the gaseous planets were in more distant orbits.

The ages of the universe, our galaxy, the solar system, and Earth can be estimated using modem scientific methods. The age of the universe can be derived from the observed relationship between the velocities of and the distances separating the galaxies. The velocities of distant galaxies can be measured very accurately, but the measurement of distances is more uncertain. Over the past few decades, measurements of the Hubble expansion have led to estimated ages for the universe of between 7 billion and 20 billion years, with the most recent and best measurements within the range of 10 billion to 15 billion years.

A disk of dust and gas, appearing as a dark band in this Hubble Space Telescope photograph, bisects a glowing nebula around a very young star in the constellation Taurus. Similar disks can be seen around other nearby stars and are thought to provide the (more...)

The age of the Milky Way galaxy has been calculated in two ways. One involves studying the observed stages of evolution of different-sized stars in globular clusters. Globular clusters occur in a faint halo surrounding the center of the Galaxy, with each cluster containing from a hundred thousand to a million stars. The very low amounts of elements heavier than hydrogen and helium in these stars indicate that they must have formed early in the history of the Galaxy, before large amounts of heavy elements were created inside the initial generations of stars and later distributed into the interstellar medium through supernova explosions (the Big Bang itself created primarily hydrogen and helium atoms). Estimates of the ages of the stars in globular clusters fall within the range of 11 billion to 16 billion years.

A second method for estimating the age of our galaxy is based on the present abundances of several long-lived radioactive elements in the solar system. Their abundances are set by their rates of production and distribution through exploding supernovas. According to these calculations, the age of our galaxy is between 9 billion and 16 billion years. Thus, both ways of estimating the age of the Milky Way galaxy agree with each other, and they also are consistent with the independently derived estimate for the age of the universe.

Radioactive elements occurring naturally in rocks and minerals also provide a means of estimating the age of the solar system and Earth. Several of these elements decay with half lives between 700 million and more than 100 billion years (the half life of an element is the time it takes for half of the element to decay radioactively into another element). Using these time-keepers, it is calculated that meteorites, which are fragments of asteroids, formed between 4.53 billion and 4.58 billion years ago (asteroids are small "planetoids" that revolve around the sun and are remnants of the solar nebula that gave rise to the sun and planets). The same radioactive time-keepers applied to the three oldest lunar samples returned to Earth by the Apollo astronauts yield ages between 4.4 billion and 4.5 billion years, providing minimum estimates for the time since the formation of the moon.

The oldest known rocks on Earth occur in northwestern Canada (3.96 billion years), but well-studied rocks nearly as old are also found in other parts of the world. In Western Australia, zircon crystals encased within younger rocks have ages as old as 4.3 billion years, making these tiny crystals the oldest materials so far found on Earth.

The best estimates of Earth's age are obtained by calculating the time required for development of the observed lead isotopes in Earth's oldest lead ores. These estimates yield 4.54 billion years as the age of Earth and of meteorites, and hence of the solar system.

The origins of life cannot be dated as precisely, but there is evidence that bacteria-like organisms lived on Earth 3.5 billion years ago, and they may have existed even earlier, when the first solid crust formed, almost 4 billion years ago. These early organisms must have been simpler than the organisms living today. Furthermore, before the earliest organisms there must have been structures that one would not call "alive" but that are now components of living things. Today, all living organisms store and transmit hereditary information using two kinds of molecules: DNA and RNA. Each of these molecules is in turn composed of four kinds of subunits known as nucleotides. The sequences of nucleotides in particular lengths of DNA or RNA, known as genes, direct the construction of molecules known as proteins, which in turn catalyze biochemical reactions, provide structural components for organisms, and perform many of the other functions on which life depends. Proteins consist of chains of subunits known as amino acids. The sequence of nucleotides in DNA and RNA therefore determines the sequence of amino acids in proteins; this is a central mechanism in all of biology.

Experiments conducted under conditions intended to resemble those present on primitive Earth have resulted in the production of some of the chemical components of proteins, DNA, and RNA. Some of these molecules also have been detected in meteorites from outer space and in interstellar space by astronomers using radio-telescopes. Scientists have concluded that the "building blocks of life" could have been available early in Earth's history.

An important new research avenue has opened with the discovery that certain molecules made of RNA, called ribozymes, can act as catalysts in modem cells. It previously had been thought that only proteins could serve as the catalysts required to carry out specific biochemical functions. Thus, in the early prebiotic world, RNA molecules could have been "autocatalytic"—that is, they could have replicated themselves well before there were any protein catalysts (called enzymes).

Laboratory experiments demonstrate that replicating autocatalytic RNA molecules undergo spontaneous changes and that the variants of RNA molecules with the greatest autocatalytic activity come to prevail in their environments. Some scientists favor the hypothesis that there was an early "RNA world," and they are testing models that lead from RNA to the synthesis of simple DNA and protein molecules. These assemblages of molecules eventually could have become packaged within membranes, thus making up "protocells"—early versions of very simple cells.

For those who are studying the origin of life, the question is no longer whether life could have originated by chemical processes involving nonbiological components. The question instead has become which of many pathways might have been followed to produce the first cells.

Will we ever be able to identify the path of chemical evolution that succeeded in initiating life on Earth? Scientists are designing experiments and speculating about how early Earth could have provided a hospitable site for the segregation of molecules in units that might have been the first living systems. The recent speculation includes the possibility that the first living cells might have arisen on Mars, seeding Earth via the many meteorites that are known to travel from Mars to our planet.

Of course, even if a living cell were to be made in the laboratory, it would not prove that nature followed the same pathway billions of years ago. But it is the job of science to provide plausible natural explanations for natural phenomena. The study of the origin of life is a very active research area in which important progress is being made, although the consensus among scientists is that none of the current hypotheses has thus far been confirmed. The history of science shows that seemingly intractable problems like this one may become amenable to solution later, as a result of advances in theory, instrumentation, or the discovery of new facts.

Creationist Views of the Origin of the Universe, Earth, and Life

Many religious persons, including many scientists, hold that God created the universe and the various processes driving physical and biological evolution and that these processes then resulted in the creation of galaxies, our solar system, and life on Earth. This belief, which sometimes is termed "theistic evolution," is not in disagreement with scientific explanations of evolution. Indeed, it reflects the remarkable and inspiring character of the physical universe revealed by cosmology, paleontology, molecular biology, and many other scientific disciplines.

The advocates of "creation science" hold a variety of viewpoints. Some claim that Earth and the universe are relatively young, perhaps only 6,000 to 10,000 years old. These individuals often believe that the present physical form of Earth can be explained by "catastrophism," including a worldwide flood, and that all living things (including humans) were created miraculously, essentially in the forms we now find them.

Other advocates of creation science are willing to accept that Earth, the planets, and the stars may have existed for millions of years. But they argue that the various types of organisms, and especially humans, could only have come about with supernatural intervention, because they show "intelligent design."

In this booklet, both these "Young Earth" and "Old Earth" views are referred to as "creationism" or "special creation."

There are no valid scientific data or calculations to substantiate the belief that Earth was created just a few thousand years ago. This document has summarized the vast amount of evidence for the great age of the universe, our galaxy, the solar system, and Earth from astronomy, astrophysics, nuclear physics, geology, geochemistry, and geophysics. Independent scientific methods consistently give an age for Earth and the solar system of about 5 billion years, and an age for our galaxy and the universe that is two to three times greater. These conclusions make the origin of the universe as a whole intelligible, lend coherence to many different branches of science, and form the core conclusions of a remarkable body of knowledge about the origins and behavior of the physical world.

Nor is there any evidence that the entire geological record, with its orderly succession of fossils, is the product of a single universal flood that occurred a few thousand years ago, lasted a little longer than a year, and covered the highest mountains to a depth of several meters. On the contrary, intertidal and terrestrial deposits demonstrate that at no recorded time in the past has the entire planet been under water. Moreover, a universal flood of sufficient magnitude to form the sedimentary rocks seen today, which together are many kilometers thick, would require a volume of water far greater than has ever existed on and in Earth, at least since the formation of the first known solid crust about 4 billion years ago. The belief that Earth's sediments, with their fossils, were deposited in an orderly sequence in a year's time defies all geological observations and physical principles concerning sedimentation rates and possible quantities of suspended solid matter.

Geologists have constructed a detailed history of sediment deposition that links particular bodies of rock in the crust of Earth to particular environments and processes. If petroleum geologists could find more oil and gas by interpreting the record of sedimentary rocks as having resulted from a single flood, they would certainly favor the idea of such a flood, but they do not. Instead, these practical workers agree with academic geologists about the nature of depositional environments and geological time. Petroleum geologists have been pioneers in the recognition of fossil deposits that were formed over millions of years in such environments as meandering rivers, deltas, sandy barrier beaches, and coral reefs.

The example of petroleum geology demonstrates one of the great strengths of science. By using knowledge of the natural world to predict the consequences of our actions, science makes it possible to solve problems and create opportunities using technology. The detailed knowledge required to sustain our civilization could only have been derived through scientific investigation.

The arguments of creationists are not driven by evidence that can be observed in the natural world. Special creation or supernatural intervention is not subjectable to meaningful tests, which require predicting plausible results and then checking these results through observation and experimentation. Indeed, claims of "special creation" reverse the scientific process. The explanation is seen as unalterable, and evidence is sought only to support a particular conclusion by whatever means possible.

• Cite this Page National Academy of Sciences (US). Science and Creationism: A View from the National Academy of Sciences: Second Edition. Washington (DC): National Academies Press (US); 1999. The Origin of the Universe, Earth, and Life.
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Defining life and evolution: Essay on the origin, expansion, and evolution of living matter

Affiliation.

• 1 Institute of Molecular Biology and Genetics of the National Academy of Sciences of Ukraine, Kyiv, 03143, Ukraine. Electronic address: [email protected].
• PMID: 34352326
• DOI: 10.1016/j.biosystems.2021.104500

This essay aims to define the origin, expansion, and evolution of living matter. The first formations, identified as remains, fossils, traces etc. of life are almost as old as the Earth itself. During four billion years, life on the Earth has continuously existed and been implemented in the range of conditions, ensuring the liquid state of water. During the entire period of life existence, its evolution was proceeding with the tendency of multidirectionality, after each catastrophe tending to the diversity and vastness of distribution, and all the currently living species, regardless of their complexity, have the same evolutionary age. The property of reproductive surplus (multiplication) is inherent in all the living matter. The reproduction of all the living matter is implemented via the "development" - a process of continuous occurrence of something new that did not exist in the previous moment in the reproduced individual at each specific moment of time with the tendency towards the reproduction of a "copy". In its fundamental basis, Life is based on a programme, its material support is implemented and exists not in the field of causative-consecutive events, but in the field of programmed-causative-consecutive events. This predetermines the "biology laws", the behaviour of the material constituent of Life at each time period, and the future of the material constituent of life.

Keywords: Development; Evolution; Genetic program; Origin of life; biological Complexity.

Copyright © 2021 Elsevier B.V. All rights reserved.

• Biological Evolution*
• Biology / methods
• Earth, Planet
• Evolution, Chemical*
• Extraterrestrial Environment
• Models, Biological
• Origin of Life*
• Reproduction / physiology
• Time Factors

Essay on Origin Of Life

Students are often asked to write an essay on Origin Of Life in their schools and colleges. And if you’re also looking for the same, we have created 100-word, 250-word, and 500-word essays on the topic.

Let’s take a look…

100 Words Essay on Origin Of Life

What is life.

Life is everything that can breathe, grow, reproduce, and change. It includes tiny bacteria, plants, animals, and humans. Scientists are curious about how life started on Earth.

Early Earth Conditions

Our planet formed about 4.5 billion years ago. It was very hot, with volcanoes and a sea of melted rocks. Over time, it cooled down, water appeared, and the right conditions for life were set.

The First Living Things

The first life forms were probably simple cells. They appeared around 3.5 billion years ago. These cells could make copies of themselves and were the start of all living things.

Where Did Life Come From?

Some scientists think life’s building blocks came from space, while others believe they formed in Earth’s oceans. These tiny parts joined together to make the first life.

Still a Mystery

Even today, how life exactly began is not known. Scientists keep studying and finding clues. It’s one of the biggest questions we’re trying to answer.

250 Words Essay on Origin Of Life

What is the origin of life.

The origin of life is a big question that has puzzled people for a long time. It is about how the first tiny living things appeared on Earth billions of years ago. Scientists think the Earth is about 4.5 billion years old, and life started after the planet cooled down and had oceans.

The First Building Blocks

Life started very simple. Before there were plants and animals, there were small chemicals that joined together in the water. These chemicals formed the building blocks of life, like the first simple cells. Think of it like putting together pieces of a puzzle. When the pieces fit just right, you get the start of life.

From Simple to Complex

The first life forms were probably not like anything alive today. They were much simpler. Over a very long time, these simple life forms changed little by little. They became more complex and turned into the many different kinds of plants and animals we see now. This process is called evolution.

Even with all the science we have, no one knows exactly how the first life started. There are many ideas, but it’s hard to prove them. Scientists keep studying this mystery, hoping to find more clues.

In Conclusion

The story of how life began is like a huge puzzle that we are still putting together. It’s an exciting story that shows just how amazing our planet is, with life that started so simple and grew into the rich variety we know today.

500 Words Essay on Origin Of Life

The origin of life is a big question that has puzzled people for a very long time. It’s about how living things first started on our planet, Earth. Imagine a world billions of years ago with no animals, plants, or people. It’s hard to think about, but that’s how things were before life began.

The Early Earth

Our planet formed about 4.5 billion years ago. It was very different from what we see now. It was hot, with lots of volcanoes and a sea of lava. The air was full of gases like carbon dioxide, nitrogen, and water vapor. There was no oxygen to breathe. In this harsh world, the first tiny steps toward life were taken.

From Non-living to Living

Scientists believe that the first living things were very simple. They were not animals or plants but tiny bits that could make copies of themselves. This happened in the water, maybe near hot underwater vents or small pools. These bits were made from chemicals that joined together in just the right way. When they made copies of themselves, life slowly started to grow and change.

The Soup Theory

One idea about how life began is called the “soup theory.” It suggests that Earth’s early oceans were like a big soup full of different chemicals. With energy from the sun, lightning, or volcanoes, these chemicals formed the building blocks of life. These building blocks then joined together to make the first simple living things.

The Space Idea

Some people think that the ingredients for life came from space. Tiny dust particles from comets or meteorites could have brought important chemicals to Earth. These space chemicals might have helped start life when they mixed with Earth’s own chemicals.

The First Cells

The first real living things were probably cells. A cell is like a tiny bag that holds all the parts needed for life. The first cells were very simple, but over time they became more complex. Some learned to use the sun’s energy, and others learned to eat different things.

Life Gets More Complex

Once the first cells were here, life started to get more interesting. Cells joined together to make bigger things. Some of these became plants, others became animals, and life spread to every part of the planet. The air slowly filled with oxygen, which helped new kinds of life to start.

The story of how life began is still not fully known. Scientists are like detectives, looking for clues in rocks, fossils, and even in space. They use experiments to test their ideas about how life could have started. It’s a big mystery, but piece by piece, we’re learning more about the amazing start of life on Earth.

This story of life’s beginning shows how from simple bits and pieces, the rich and diverse world we know today came to be. It’s a journey of billions of years, from the first tiny cells to the huge variety of life we see around us. And it’s a journey that’s still going on, as life continues to change and evolve.

That’s it! I hope the essay helped you.

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• Essay on Origin Of Language
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Write an essay on origin of life.

The origin of the first form of life has been an intriguing concept for many years. different theories and experimental proofs were forwarded by different scientists during the time interval. some of these theories were rejected as they failed to provide shreds of evidence while some others were accepted. however, there is no theory that could provide a wholesome view of the origin of life. the following theories have been suggested over the years: 1. theory of special creation- this theory suggests that all the living forms were created as it is by god. different religions have different narratives as fas as this theory is concerned. there is no scientific ground for this theory. 2. theory of spontaneous generation- this theory suggested for the origin of living forms from the non-living or inanimate objects. aristotle, epicurus, vel holmont are some of the supporters. they believed that a slice of rotten meat gave birth to the maggots. this was disapproved. 3. theory of panspermia- this theory suggested by richter in 1865 and proposed that life reached the earth from other cosmic bodies. 4. theory of biochemical evolution or materialistic theory- this theory was suggested by oparin in 1923 and haldane in 1928. it suggested that primitive earth was reducing in nature due to the absence of oxygen and several chemicals condensed together in oceans, warmed by hot temperature, formed a 'primordial' soup' in which the first living cell took its form. several amino acids, nucleic acids, sugars and other organic and inorganic molecules together formed coacervated that were capable of absorbing water and nutrients and perform budding. these kept on uniting with more and more molecules and formed the first living cell. the theory of biochemical origin had been experimentally supported by urey and miller, where they developed primitive earth-like conditions by providing lightning, water vapors, and inorganic molecules and obtained the organic molecules. hence, it can be concluded that a little insight exists about the origin of life but there are still more possibilities to explore. with the advancement in scientific technologies, there are chances of gathering more pieces of evidence in this regard..

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