Biological Sciences
Origin of Life on Earth
The origin of life on Earth is a complex and ongoing scientific inquiry into how life first emerged on our planet. Scientists study various hypotheses, such as the primordial soup theory and the deep-sea vent theory, to understand the chemical and environmental conditions that may have led to the formation of the first living organisms. This field of research seeks to unravel the fundamental processes that gave rise to life as we know it.
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11 Key excerpts on "Origin of Life on Earth"
eBook - PDF- Natarajan Ishwaran(Author)
- 2012(Publication Date)
- IntechOpen(Publisher)
Part 1 Perspectives on Origins and Evolution 1 Early Biosphere: Origin and Evolution Vladimir F. Levchenko, Alexander B. Kazansky, Marat A. Sabirov and Eugenia M. Semenova Laboratory of Evolution Modeling, Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St. Petersburg Russian Federation 1. Introduction We argue that the process of the origin and evolution of living organisms is indivisible from the process of the origin and evolution of biosphere, the global planetary system. The most general features of biosphere evolution as a directed process are formulated in the principle of “bio-actualism”. It is demonstrated, that this principle, stated for Phanerozoic eon, hold for early biosphere up to the period of biosphere coming into being. To support this thesis we considered an episode of pre-Cambrian history – Vendian phytoplanktonic crisis. Traditionally, the problem of the Origin of Life on Earth is the study of how biological life arose from inorganic matter and primary living organisms spread around the planet. Some philosophers and scientists such as Helmholtz and Arrhenius proposed the hypothesis of so-called “panspermia” and place the origin of life outside the Earth somewhere in cosmos. We suggest that such approaches are naive in view of modern progress of life sciences and astrophysics. It is clear that occasional appearance of some living forms (organisms) on any planet doesn’t mean they will survive, settle and evolve there. These conceptions ignore the problem of longtime existence and evolution of the earliest forms of life on the Earth. Moreover, they overlook the problem of the origin of the biosphere – unique milieu for early organisms survivorship and reproduction. Therefore we suppose that origin of earthly life and the origin of the biosphere are aspects of a whole indivisible process (Levchenko, 2010, 2011).
eBook - PDFWhat is Life? On Earth and Beyond
On Earth and Beyond
- Andreas Losch(Author)
- 2017(Publication Date)
- Cambridge University Press(Publisher)
Then we will summarize our current understanding of the condi- tions that led from simple, abiotically synthesized monomers to some of the earliest chemical steps from which the basic metabolic steps first originated, and ultimately to macromolecules. A model is presented for the development of replicative sys- tems from random polymers that evolved through mutation and selection. Hence one can say that the origins of life mark the start of biological evolution. We present here a scheme based on simulation experiments and explanations in progress from which one can develop essential concepts of prebiotic synthesis, self- assembly of organic molecules, primeval catalysis and template-directed synthesis that can lead to general epistemological principles in the study of the origins of life. 1.1 The Concept of Origin Over the centuries, various ways of thinking have attempted to answer the question of origins, be they origins of the universe, of the living world or of human beings. The term origin has at least two meanings: (i) that which is located at the origin, at the beginning, (ii) that which is the basis, the foundation on which something is based. The universe and the solar system were formed billions of years ago in the great- est chaos. This is how Hesiode describes the origin of the world (Hesiode, 2001, 1 Reflections on Origins, Life, and the Origins of Life 15 Théogonie, 114–22): “at first arises Beance [the void], and then the Earth (Gaia) with broad sides, forever a robust foundation for all of us”. In the 1970s, Jim Lovelock and Lynn Margulis summarized the Greek myth in an ecological sense, to try to redraw the “basis” and the living tissue written within it. In this “Gaia hypothesis” life is tightly connected to the geochemical environment; it is the main message that has become famous in the climatic evolution of today, on which the survival of numerous species depends. Accordingly, biodiversity draws its origins from the origins of life itself.
eBook - PDF- Harry Y. McSween, Jr, Jeffrey E. Moersch, Devon M. Burr, William M. Dunne, Joshua P. Emery, Linda C. Kah, Molly C. McCanta(Authors)
- 2019(Publication Date)
- Cambridge University Press(Publisher)
16 Astrobiology: A Planetary Perspective on Life At its root, the word “astrobiology” means “biology of the stars.” It is the branch of science that concerns the origin and evolution of life on Earth – the only place that, at present, we are certain life exists – and the potential for life to be distributed across the Universe. In this chapter, we explore the evolutionary relationships of life on Earth and review the necessary ingredients and permissible environmental conditions for the origin and evolution of life. We also discuss the characteristics of early life on Earth, and the physical and geochemical evidence for life that might be used to target habitable environments – and potentially to detect evidence of life – elsewhere in the Universe. 16.1 The Diversity of Life In 2003, the Hubble Space Telescope focused its lens at a single, dark and seemingly featureless spot in the Uni- verse. At the end of 11 days, Hubble had gathered enough visible, near-infrared, and UV light to identify thousands of new galaxies, each containing billions of individual stars (Figure 16.1). This astounding image brings to mind an idea first articulated by Metrodorus in 400 BC, that “it is unnatural in a large field to have only one stalk of wheat, and in the infinite universe, only one living world.” This astounding image brought new life to field of astrobiology. Among the many challenges of astrobiology is finding a solution to the seemingly simple question of what is life? Typically, we consider life as a series of observable characteristics: life has an ordered structure (cells), built around a chemical blueprint (genetic material), that responds to its environment; life utilizes energy (metab- olism) and shows growth; life is capable of reproduction. Although these characteristics are helpful in considering what to look for when investigating the potential for life in terrestrial and extraterrestrial environments, none of these characteristics are unique to life.
eBook - PDF- Tuomas E. Tahko(Author)
- 2011(Publication Date)
- Cambridge University Press(Publisher)
174 chapter 11 The origin of life and the definition of life Storrs McCall 11.1 Life’s origin, and the division between life and non-life The physicist Paul Davies gives an excellent, eloquent account of the ori- gin of life in his book The 5th Miracle (1999). Davies’s principal thesis is that although nothing rules out the possibility of life having originated on some other planet (e.g. Mars), the oldest forms of life on Earth consist of bacteria and other micro-organisms which eat unappetizing substances like sulphur and hydrogen sulphide and live in scalding volcanic jets four kilometres down at the bottom of the sea. These jets are known as ‘black smokers’ (Davies 1999: 166–86). Such organisms have probably existed on Earth for the last 3 or 4 billion years, and modern life-forms, which live in environments containing oxygen and derive energy directly or indirectly from sunlight, have literally ‘ascended from the depths’. Such an account flies in the face of more traditional origin-of-life Edens located on the surface of the Earth, or in atmospheres containing methane, hydrogen, and ammonia (Davies 1999: 86–7). But for heat-loving organisms living in rock crevices at the bottom of the sea, the Hades of a sulphurous ther- mal jet was doubtless heaven enough. The problem Davies sets himself is to imagine conditions in the deep past which would have favoured, or at least permitted, the emergence of DNA and the manufacture of proteins by unicellular organisms. With DNA and protein-manufacture we have life: without them, merely phys- ics and chemistry. Why is this? The reason is, according to Davies, that only with DNA and RNA do we arrive at the encoding of information, and the distinction between hardware and software, that separates living from non-living matter. DNA is built up out of long sequences composed of the four bases A (adenine), C (cytosine), G (guanine), and T (thym- ine). In the so-called genetic code a triplet composed of three bases, e.g.
eBook - PDFGenetics of Original Sin
The Impact of Natural Selection on the Future of Humanity
- Christian de Duve, Neil Patterson, Edward O. Wilson(Authors)
- 2010(Publication Date)
- Yale University Press(Publisher)
The Origin of Life 21 Finally, at some undetermined stage, these systems would have to become enclosed within an envelope, or membrane, to give rise to the first protocells. All these events must have taken place when life first arose on our young planet. How and in what order is totally unknown. Also unknown is the manner in which the first protocells progressively evolved into the last universal com-mon ancestor of all living beings, or LUCA, which, must, by Fig. 2.1. The origin of life. This process may be defined as the chemical pathway, so far unknown, that has led from certain organic products, which form everywhere in the universe, to the last universal com-mon ancestor (LUCA) of all life on Earth. This pathway may be divided into two stages separated by the appearance of RNA (or, in a more general fashion, of the first replicable information-bearing molecule). The first stage must have depended exclusively on chemistry. In the second, selection was added to chemistry (see chapter 7). 22 The History of Life on Earth definition, have possessed all the main properties living or-ganisms have in common and no doubt inherited from this common ancestor. There are plenty of challenges for future investigations. Whether these challenges will ever be successfully overcome cannot be predicted at this time. Today, the prospects seem bleak. On the other hand, experience has shown that a single breakthrough sometimes suddenly opens immense fields to scientific exploration. This has happened time and again, often with people exclaiming a posteriori: “Why didn’t I think of that?” 3 The Evolution of Life B orn more than three and a half billion years ago, life remained unicellular during more than two and a half billion years, more than two-thirds of its exis-tence on Earth. During all that time, microbes, or-ganisms visible only with a microscope, were the only ones present on our planet.
eBook - PDFEvolution
The First Four Billion Years
- Michael Ruse, Joseph Travis, Michael Ruse, Joseph Travis(Authors)
- 2011(Publication Date)
- Belknap Press(Publisher)
The early Archean fossil record speaks for the relatively short timescale re-quired for the origin and early evolution of life on earth and suggests that the critical factor may have been the presence of liquid water, which became pos-sible as soon as the planet’s surface finally cooled below the boiling point of water. Unfortunately, there is no geological evidence of the environmental conditions on the early earth at the time of the origin of life, nor are any mo-lecular or physical remnants preserved that provide information about the evolutionary processes that preceded the appearance of the first cellular or-ganisms found in the early fossil record. Direct information is generally lack-ing not only on the composition of the terrestrial atmosphere during the period of the origin of life but also on the temperature, ocean pH, and other general and local environmental conditions that may or may not have been important for the emergence of living systems. The Primitive Earth Environment Considerable progress has been made in our understanding of environmental conditions of the early earth and how the transition from abiotic to biotic chemistry may have occurred (for example, see Bada 2004). Nevertheless, there are still enormous gaps in our description of how the simple organic compounds associated with life as we know it reacted to generate the first liv-ing entities and how these in turn evolved into organisms that left behind ac-tual evidence of their existence in the rock record. To evaluate how life may have begun on earth, we must access what the planet was like during its early history and under what conditions the processes thought to be involved in the origin of life took place. Life as we know it depends on the presence of liquid water and organic polymers such as nucleic acids and proteins.
eBook - PDF- Carol Christian, Jean-René Roy(Authors)
- 2017(Publication Date)
- Cambridge University Press(Publisher)
Stanley Miller and the set-up for the Miller–Urey experiment of 1952. How did life begin on Earth? 229 an atmosphere. Re-analysis of the Miller experiments showed that synthesis in a volcanic atmosphere (such as that of the early Earth) is even more promising [Johnson 2008, Indiana University 2008]. Even if scientists have not yet managed to synthesize the proteins, the lipids, or the nucleic acids themselves, that early experiment would seem to have pointed the way down a promising path. Nevertheless, for life to get started, it would never be enough simply to produce batches of elementary organic molecules; they would have to encounter each other and interact to form the more complex molecules of life. A liquid is a perfect medium for such interactions, provided that it is a good solvent so that the molecules diffuse well and do not precipitate out. Water, thanks to the polar nature of its molecule and its abundance on Earth, is ideal for that role (Q. 180). So it is generally assumed that life on Earth arose in water, which is an essential component of all known living cells and which, indeed, constitutes 70% to 95% of a cell’s makeup. Finally, a physical boundary between living and non-living matter is needed, between the components of the cell and the hostile external environment. That role is played by a cell’s protective membrane. Exactly how the first membrane formed around the nascent cell is still a mystery, but it is probable that the very first organisms did not fabricate their membranes themselves, but instead developed inside the naturally occurring envelopes, such as fatty bubbles, that tend to form in watery mediums. Once life had become established, it remained essentially unicellular for a very long time – over 3 billion years. The first evidence for multicellular organisms is the enigmatic Ediacaran fauna, which emerged in the Precambrian era about 635 to 540 million years ago.
eBook - PDF- Chris Impey, Jonathan Lunine, José Funes(Authors)
- 2012(Publication Date)
- Cambridge University Press(Publisher)
Until this paradox is resolved by some appropriate combination of chemistry and environment, the “origins” problem will not be solved. Synthesizing life from scratch Of course, even if a laboratory experiment does generate RNA from plau- sible prebiotic precursors, the result need not offer us a constraint-by-origin view of what forms life might take universally. After all, molecules other than RNA might be able to simultaneously support genetics and catalysis. These too might be able to straddle non-Darwinian and Darwinian chemistry in a way that leads to their own form of life, possibly quite different from the life we know on Earth, and possibly in environments quite different from those found on early Earth. This observation suggests a fourth approach to understanding life as a universal. This approach, represented by the right wedge in Figure 2.1, comes under the title “synthetic biology.” Synthesis, especially in chemistry, reflects first a definition of understanding as an ability to create. If we truly understand chemical systems that support Darwinian evolution, we should be able to construct one of our own in the laboratory. If the NASA definition-theory of life is on point, this artificial system should be able to re-create all of the properties that we value in life. Conversely, if we cannot build life from scratch, then we must not understand completely what life is. Further, de novo synthesis provides us with candidate Darwinian molecules that are different in structure from those found in terran biology. Through syn- thesis, we can ask: What kinds of molecules other than standard DNA and RNA might support Darwinian evolution? This takes us in the direction of universality, at least as far as our imagination and synthetic technology allow. Underlying the famous double helix of Watson and Crick (Watson and Crick 1953) are two simple rules for genetics, rules that describe complementarity between two DNA strands.
eBook - PDFLife's Origin
The Beginnings of Biological Evolution
- J. William Schopf(Author)
- 2002(Publication Date)
- University of California Press(Publisher)
chapter 1 Historical Understanding of Life’s Beginnings john oró what is life? There are three major singularities in the world—the observable uni-verse, life on Earth, and human beings. For the most part, we agree on concepts of what the cosmos and human beings are, but we have reached no consensus on what life is. It is easier to recognize life, in all its common forms, than it is to define it. In 1976, during NASA’s Viking Project to Mars, the late Carl Sagan and I were at the Jet Propulsion Laboratory in Pasadena, California, discussing this very problem. Asked if we would actually recognize life on Mars were we lucky enough to encounter it, Carl answered with ebullient humor: “John! If a herd of elephants stampeded across the field in front of the camera, we would not have any doubt about the existence of life on the Red Planet. Is that simple enough?” Well, perhaps. But barring stampeding elephants, probably not. Still, life can be defined in relatively simple terms, as many encyclopedias have done. A common definition, for example, is that “Life is a dynamic state of organized matter characterized basically by its capacity for adaptation and evolution in response to changes in the environment, and its capacity for reproduction to give rise to new life. Such a state is a consequence of metabolic reactions (anabolism and catabolism) and of the interaction of the living organism with other organisms and the environment.” More generally, however, we describe the nature of 7 life in terms of the main attributes that characterize living systems, as follows: 1. Dynamic, self-organized, independent structural entities 2. Made of water (H 2 O), the biogenic elements CHONSP (carbon, hydrogen, oxygen, nitrogen, sulfur, and phospho-rus), and organic molecules 3. Able to extract and recycle matter and energy from the environment 4. Self-reproducing by translation of stereospecific informa-tional polymers 5.
eBook - PDF- Cornelius A. Tobias, John H. Lawrence, Cornelius A. Tobias, John H. Lawrence(Authors)
- 2013(Publication Date)
- Academic Press(Publisher)
Eventually one must come to a point Origin of Life on Earth AND ELSEWHERE 317 at which what we would have called a living thing, if we were able to view it from a distance, was a variety of aggregates of matter, some of which we would call alive and some of which we would not. Further back extrapolation leads to varieties of things even more primitive, none of which we would call alive. This is the idea of a living organism developing in an evolutionary sequence of events in time. At some point, when material with a suffi-cient number of the desired properties had gathered around in a single region of space (a single system) we would call it alive. This is the notion that Darwin recognized even in his very earliest works. Shortly after the publication of Darwin's thesis, there was another publication, this time by a chemist, Louis Pasteur, around 1863. He did an experi-ment in which he showed definitively that no life could originate on the surface of the earth under the conditions that then existed, unless it came from pre-existing life. The Darwinian notion was completely over-shadowed by the Pasteur dictum that one could not obtain living material except from living material. Therefore, no one dared think seriously that living material had some other origin than from living material. It came to an end at that point. I wondered about that point—about why Darwin never did express himself explicitly on this matter—but it turns out that he did, and I found here his opinion on the origin of life, written in a letter by Charles Darwin to George Wallich in 1882: You expressed quite correctly my views where you say that I had intentionally left the question of the Origin of Life uncanvassed as being altogether ultra vires in the present state of our knowledge, and that I dealt only with the manner of succession. I have met with no evidence that seems in the least trustworthy, in favour of so-called Spontaneous generation.
eBook - PDFThe Emergence of Life
From Chemical Origins to Synthetic Biology
- Pier Luigi Luisi(Author)
- 2016(Publication Date)
- Cambridge University Press(Publisher)
fascinated by the depth of the challenge, top scientists among them attracted by the top problem of chemistry as a science in the 21th century: the creation of artificial chemical life in the laboratory. Creating artificial chemical life and searching for the origin of the life we know are two sides of the same coin. I may be forgiven for self- quoting what I had written in a recent review: “We’ll never be able to know” is a truism that leads to resignation with respect to any experimental effort to search for the chemistry of life’ s origin. But such resignation runs radically counter to the challenge imposed upon chemistry as a natural science. Notwithstanding the prognosis according to which the shortest path to understanding the metamorphosis of the chemical into the biological is by way of experimental modeling of “artificial chemical life,” the scientific search for the route nature adopted in creating the life we know will arguably never truly end. It is, after all, part of the search for our own origin. PLL: What do you suggest to younger people engaging in the field of the origin of life? ALBERT ESCHENMOSER: What I would propose to young chemists entering the field is: Focus in your research on problems that promise to have dual relevance, namely, work on questions that can lead – to be sure – to results relevant to the origin of life problem, but not only: these results should at the same time constitute valid scientific contri- butions to contemporary chemistry. Relevance to the origin of life problem is potential relevance, and it may turn out to be short-lived; a result that is acknowledged as contribution to contemporary chemistry will be understood and appreciated by many, it will consolidate your career.
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