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1. Discuss the following theories in detail. Support or refute with experiments or examples.
A. Traditionally, many cultures have believed that life was put on Earth by divine (relating to a god or gods) forces, as the act of a creator or creators. Belief in divine creation is common to many of the world’s major religions, thought the accounts of creation vary from one religion to another. By all accounts of divine creation, the process that gave rise to life on Earth was driven by forces that cannot be explained by science. Philosophers have debated the essence of these forces for centuries. It is important to understand, however, that a belief is not the same thing as a scientific hypothesis. The essence of any scientific hypothesis is that the proposed idea is subject to test – that the idea could, in principle at least, be proven false. Science is a way of investigating the natural world (through observation and experimentation) and forming general rules about how things happen. A belief in divine creation, however, is not a scientific hypothesis that can be tested. Try to imagine an observation that would disprove divine creation. Whatever you propose, it is always possible to argue that a divine agent simply made things appear the way they do. Because the idea that life originated through divine creation cannot be tested by scientific methods, it falls outside the realm of science. This is not to say that the belief is wrong, but rather that science can never test it.
B. Most of the early biologists, from time of Aristotle, believed that simple living things, such as worms, beetles, frogs, and salamanders, could originate spontaneously in dust or mud, that rodents formed from moist grain, and that plant lice condensed from a dewdrop. In the seventeenth century, Francesco Redi performed a famous experiment in which he put out decaying meat in a group of wide-mouthed jars - some with lids, some covered by a fine veil, and some open - and demonstrated that maggots arose only where flies were able to lay their eggs.By the nineteenth century, no - scientist continued to believe that complex organisms rose spontaneously. The advent of microscopy, however, led a vigorous renewal of belief in the spontaneous generation of very simple organisms. It was necessary only to put decomposing substances in a warm place for a short time and tiny " live beasts" appeared under the lens, before one’s very eyes. By 1860, the controversy had become so spirited that the Paris Academy of Sciences offered a prize for experiments that would throw a new light on the question. The prize was claimed in 1864 by Louis Pasteur, who devised experiments to show that microorganisms appeared only as contaminants from the air and not "spontaneously" as his opponents claimed. In his experiments he used swan-necked flasks, which permitted the entrance of oxygen, thought to be necessary for life, but which, in their long, curving necks, trapped bacteria, fungal spores, and other microbial life and thereby protected the contents of the flasks from contamination. He showed that if the liquid in the flask was boiled ( which killed the organisms already present) and the neck of the flask was allowed to remain intact, no microorganisms would appear. Only if the curved neck of the flask was broken off, permitting contaminants to enter the flask, did microorganisms appear.
In retrospect, Pasteur’s well-planned experiments were so decisive because the broad question of whether or not spontaneous generation had ever occurred was reduced to the simpler question of whether or not it occurred under the specific conditions claimed for it. Pasteur’s experiments answered only the latter question, but the results were so dramatic that for many years very few scientists were able to think of the possibility that under quite different conditions, when the earth was very young, some form of "spontaneous generation" might indeed have taken place. The question of the origin of the first living systems remained unasked until well into the 20th century.
C. Until very recently, the earliest fossil organisms known were a mere 600 million years old, and for a long time after the publication of The Origin of Species, biologists regarded the earliest events in the history of life as chapters that would probably remain forever closed to scientific investigation.
Two developments, however, have greatly improved our long-distance vision. The first was the formulation of a testable hypothesis about the event’s preceding life’s origins. This hypothesis generated questions for which answers could be sought experimentally. The results of the initial experimental tests led to the formulation of further hypotheses and to additional experiments, a process that continues today as scientists in many laboratories explore the question of life’s origins. The second development was the discovery of fossilized cells more than 3 billion years old.
The testable hypothesis was offered by the Russian biochemist Oparin. According to Oparin, the appearance of life was preceded by a long period of what is sometimes called chemical evolution. The identity of the substances, particularly gases, present in the primitive atmosphere and in the seas during this period is a matter of controversy. There is general agreement, however, on two critical issues: (1) little or no free oxygen was present and, (2) the four elements - hydrogen, oxygen, carbon and nitrogen - that make up more than 95 percent of living tissues were available in some form in the atmosphere and waters of the primitive earth.
In addition to these raw materials, energy abounded on the young earth. There was heat energy, both boiling heat and baking heat. Water vapor spewed out of the primitive seas, cooled in the upper atmosphere, collected into clouds, fell back on the crust of the earth, and steamed up again. Violent rainstorms were accompanied by lightning, which provided electrical energy. The sun bombarded the earth’s surface with high-energy particles and ultraviolet light, another form of energy. Radioactive elements within the earth released their energy into the atmosphere. Oparin hypothesized that under such conditions organic molecules were formed from the atmospheric gases and collected in a thin soup in the earth’s seas and lakes. Because there was no free oxygen present to react with and degrade these organic molecules to simple substances such as carbon dioxide (as would happed today), they tended to persist. Some of these molecules might have become locally more concentrated by the drying up of a lake or by the adhesion of the molecules to a solid surface.
Oparin published his hypothesis in 1922, but at that time biochemists were so convinced by Pasteur’s demonstration disproving spontaneous generation that the scientific community ignored his ideas. In the 1950’s the first test of Oparin’s hypothesis was performed by Stanley Miller, then a graduate student at the University of Chicago. Experiments of this sort, now repeated many times, have shown that almost any source of energy - lighting, ultraviolet radiation, or hot-volcanic ash - would have converted molecules believed to have been present on the earth’s surface into a variety of complex organic compounds. With various modifications in the experimental conditions and in the mixture of gases placed in the reaction vessel, almost all of the common amino acids have been produced, as well as the nucleotides that are the essential components of DNA and RNA.
These experiments have not proved that such organic compounds were formed spontaneously on the primitive earth, only that they could have formed. The accumulated evidence is nevertheless very great, and most biochemists now believe that, given the conditions existing on the young earth, chemical reactions producing amino acids, nucleotides and other organic molecules were inevitable.
As the concentrations of such molecules increased, bringing them into closer proximity to each other, they would have been subject to the same chemical forces that act on organic molecules today. Small organic molecules react with each other, typically in condensation reactions, to form larger molecules; moreover, such forces as hydrogen bonds and hydrophobic interactions cause these molecules to assemble themselves into more complex aggregates. In modern chemical systems - either in the laboratory or in the living organism - the more stable molecules and aggregates tend to survive and the least stable are transitory. Similarly, the compounds and aggregates that had the greatest chemical stability under the prevailing conditions on the primitive earth would have tended to survive. Hence a form of natural selection played a role in chemical evolution as well as in the biological evolution that was to follow.
From a biochemical perspective, three characteristics distinguish the living cell from other chemical systems: (1) the capacity to replicate itself, generation after generation; (2) the presence of enzymes, the complex proteins that are essential for the chemical reactions on which life depends; and (3) a membrane that separates the cell from the surrounding environment and enables it to maintain a distinct chemical identity. Which of the characteristics appeared first - and made possible the development of others - remains an open question. However, recently discovered functions of RNA suggest that the starting point may well have been the self-assembly of RNA molecules from nucleotides produced by chemical evolution.
In other studies, simulating the condition's during the earth's first billion years, Sidney W. Fox and his coworkers at the University of Miami have produced membrane bound protein structures that can carry out a few chemical reactions analogous to those of living cells. These structures are produced through a series of chemical reactions, beginning with dry mixtures of amino acids. When the mixtures are heated at moderate temperatures, polymers are formed, each of which may contain as many as 200 amino acid monomers. When these polymers are placed in an aqueous salt solution and maintained under suitable conditions, they spontaneously form proteinoid micro-spheres. The micro-spheres grow slowly by the addition of protenoid material from the solution and eventually bud off smaller micro-spheres. These micro-spheres are not living cells. Their formation, however, suggests the kinds of processes that could have given rise to self-sustaining protein entities, separated from their environment and capable of carrying out the chemical reactions necessary to maintain their physical and chemical integrity.
It is not known when the first living cells appeared on earth, but we can establish some sort of a time scale. The earliest fossils found so far which reassemble present day bacteria, have been dated at 3.4 and 3.5 billion years, about 1.1 billion years after the formation of the earth itself. Although the fossils are so small that their structure can only be visible by electron microscopy, they are sufficiently complex that it is clear that some little aggravation of chemicals had moved through the twilight zone separating the living from the non-living millions of years ago.
On the basis of astronomical studies and the explorations carried out by unmanned space vehicles, it appears that earth alone among the planets of our solar system supports life. The conditions on earth are ideal for living systems based on carbon-containing molecules. A major factor is that earth is neither too close of too far from the sun. The chemical reactions on which life - at least as we know it - depends require liquid water, and they virtually cease at very low temperatures. At high temperatures, the complex chemical compounds essential for life are too unstable to survive.
Earth's size and mass are also important factors. Planets much smaller than earth do not have enough gravitational pull to hold a protective atmosphere, and any planet much larger than earth is likely to have so dense an atmosphere that light from the sun cannot reach its surface. The earth's atmosphere blocks out many of the energetic radiation’s from the sun, which are capable of breaking the covalent bonds between carbon atoms. It does, however, permit the passage of visible light, which made possible one of the most significant steps in the evolution of complex living systems.
The energy that produced the first organic molecules came from a variety of sources on the primitive earth and in its atmosphere - heat, ultraviolet radiation’s, and electrical disturbances. When the first primitive cells or cell-like structures evolved, they regained a continuing supply of energy to maintain themselves, to grow and to reproduce. The manner in which these cells obtained energy is currently the subject of lively discussion.Modern organisms - and the cells of which they are composed - can meet their energy needs in one of two ways. Heterotrophs are organisms that are dependent upon outside sources of organic molecules for both their energy and their small building-block molecules. All animals and fungi as well as many single celled organisms, are heterotrophs. Autotrophs, by contrast are "self-feeders". They do not require organic molecules from outside sources for energy or to use as small-building block molecules, they are, instead, able to synthesize their own energy-rich organic molecules from simple inorganic substances. Most autotrophs, including plants and several different types of single-celled organisms, are photosynthetic, meaning that the energy source for their synthetic reactions is the sun. Certain groups of bacteria, however, are chemo-synthetic; these organisms capture the energy released by specific inorganic reactions to power their life processes including the synthesis of needed organic molecules.
Both heterotrophs and autotrophs seem to be represented among the earliest microfossils. It has long been said that the first living cell was an extreme heterotroph. As the primitive heterotrophs increased in number, according to this hypothesis, they began to use up the complex molecules on which their existence depended and which have taken millions of years to accumulate. As the supply of these molecules decreased, competition began. Under the pressure of this competition, cells that could make efficient use of the limited energy sources now available were more likely to survive and reproduce than cells that could not. In the course of time, other cells evolved that were able to synthesize organic molecules out of simple inorganic materials.
Recent discoveries, however, have raised the possibility that the first cells may have been either chemosynthetic or photosynthetic autotrophs rather than heterotrophs. First, several different groups of chemosynthetic bacteria have been found that would have been well suited to the conditions prevailing on the young earth. Some of these bacteria are the inhabitants of swamps, while others have been found in deep ocean trenches in areas where gases escape from fissures in the earth’s crust. There is evidence that these bacteria are the surviving representatives of very ancient group of unicellular organisms. Second, organic molecules that are, in plants, the chemical precursors of chlorophyll have been produced in experiments analogous to that performed by Miller. When these molecules are mixed with simple organic molecules in an oxygen-free environment and illuminated, primitive photosynthetic reactions occur. These reactions resemble the reactions that occur in some types photosynthetic bacteria.
Although biologists are presently unable to resolve the question whether the earliest cells were heterotrophs or autotrophs, it is certain that without the evolution of autotrophs, life on earth would soon have come to an end. In the more than 3.5 billion years since life first appeared on earth, the most successful autotrophs have been those that have evolved a system for making direct use of sun's energy in the process of photosynthesis. With the advent of photosynthesis, the flow of energy in the biosphere came to assume its dominant modern form: radiant energy from the sun channeled through photosynthetic autotrophs to all other forms of life.The cell theory is one of the foundations of modern biology. This theory states simply that (1) all living organisms are composed of one or more cells (2) the chemical reactions of a living organism, including its energy releasing processes and its biosynthetic reactions, take place within cells (3) cells arise from other cells; and (4) cells contain the hereditary information of the organisms of which they are a part, and this information is passed from parent cell to daughter cell. All available evidence indicates that there is an unbroken continuity between modern cells - and the organisms they compose - and the first primitive cells that appeared on earth.
All cells share two essential features. One is an outer membrane, the cell membrane, that separates the cell from its external environment. The other is the genetic material - the hereditary information - that directs a cell's activities and enables it to reproduce, passing on its characteristics to its offspring.The organization of the genetic material is one of the characteristics that distinguish two fundamentally distinct kinds of cells, prokaryotes and eukaryotes. In prokaryotic cells, the genetic material is in the form of a large circular molecule of DNA, with which a variety of proteins are loosely associated. This molecule is known as the chromosome. In eukaryotic cells, by contrast, the DNA is linear, forming a number of distinct chromosomes; moreover, it is tightly bound to special proteins known as histones, which are an integral part of the chromosome structure. Within the eukaryotic cell, the chromosomes are surrounded by a double membrane, the nuclear envelope, that separates them from the other cell contents in a distinct nucleus. In prokaryotes, the chromosome is not contained within a membrane-bound nucleus, although it is localized in a distinct region known as the nucleoid.
The remaining components of a cell constitute the cytoplasm. The cytoplasm contains a large variety of molecules as well as formed bodies called organelles. These specialized structures carry out particular functions within the cell. Both prokaryotes and eukaryotes contain very small organelles called ribosome’s, on which protein molecules are assembled. In addition, eukaryotes contain a variety of more complex organelles, which are often enclosed within membranes.
The cell membrane of prokaryotes is surrounded by an outer cell wall that is manufactured by the cell itself. Some eukaryotic cells, including plant cells and fungi, have cell walls, although their structure is different from that of prokaryotic cell walls. Other eukaryotic cells, including those of our own bodies and of other animals, do not have cell walls. Another feature distinguishing eukaryotes and prokaryotes is size: eukaryotic cells are usually larger than prokaryotic cells.
Modern prokaryotes include the bacteria and the cyanobacteria, a group of photosynthetic prokaryotes that were formerly known as the blue-green algae. According to the fossil record, the earliest living organisms were comparatively simple cells, resembling present-day prokaryotes. Prokaryotes were the only forms of life on this planet for almost 2 billion years until eukaryotes evolved. An example of an single-celled photosynthetic eukaryote, is the alga Chlamydomonas. It is a common inhabitant of fresh water ponds and aquariums. These organisms are small and bright green and they move very quickly with a characteristic darting motion. Being photosynthetic, they are usually found near the waters surface.
The first multi-cellular organisms, as far as can be told by the fossil record, made their appearance a mere750 million years ago. The major groups of multi-cellular organisms - such as the fungi, the plants, and the animals are thought to have evolved from different types of single-celled eukaryotes. The first colonies of cells were probably actually separate cells that lived in colonies, but were absolutely not specialized in any way. In other words, each individual maintained itself. Next a few of the cells in the colony could have become very little specialized, for example developed floating devices to keep the colony on water level. For example sponges, however, if you put a sponge in a blender it will become a sponge again, even thought the cells have been separated, thus it is not a fully specialized cell colony. With the further evolution of these cells they were unable to maintain their food supply, thus certain cells became specialized, by natural selection, to distribute nutrients to the different cells. Further, the cells became specialized, such as respiration, reproduction, food digestion, exertion of deadly materials and not needed materials, movement, and many other specialized functions that the cell colony became a tissue and thus changed from colony to a multi-cellular state.
D1. The knowledge of the Mayan people pertaining to astronomy was highly developed. They even tried such things as brain surgery. Did they just think this all up or was it given to them by aliens? The Mayans could have thought this stuff up and there were such pursuing questions as how were huge boulders moved by ancient people and that’s been figured out so the Mayans probably just were smart and ingenious. The Mayans also drew huge arthropods onto the fields that were up to 35 miles wide of spider, etc. that can only be seen from space or high above the ground. Did the Mayans draw these for these aliens to see? Probably not, since they firmly believed in the existence of gods and supernatural beings that were suppose to look down on them from the skies, this is deducted from their writings and records. The Mayans were probably drawing this or their "gods" to see, but it might have been that their gods were actually aliens that came to visit them and that was their launch site. If you go back into literature you cannot find flying saucers or anything of the type until the War of The Worlds by H. G. Wells was broadcasted live on the radio in 1947, the beginning of this mania. This broadcasting was told that it was fake but some people tuned in late and didn’t know that so some people might have thought that the aliens are coming to take them away. Was this all a coincidence, or did H. G. Wells have an encounter with a flying saucer that made him believe? It was probably just a work of fiction which had various deductions. Maybe aliens know about the Earth in some other way or they came to visit and it is unknown? This could also be possible, but cannot be proved or disproved.
It is one gigantic universe. A light year alone consists of 9,460,730,476,000 kilometers or 4,295,171,636,000 miles and a light-year is a relatively small unit when it comes to measuring the universe. The universe is thought to be 15,000,000,000 light-years in radius or 103,663,967,400,000,000,000,000 kilometers (64,427,574,520,000,000,000,000 miles) and the universe has expanded since. The proportions and numbers are huge as are the distances. To the closest star (Proximate Centari) it is 4.3 light years or 40,681,141,050,000 kilometers and that’s quite far away. The only was to get to the star would be to warp space and time by using as black hole to bend space. A black hole is just like taking a short cut and you don’t really go faster than the speed of light. If warping space is possible, then If Warp 9 (Star Trek) is suppose to be the speed of light to the 9th power than that would be 19,683,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 kilometers per second and that doesn’t make sense since you could get across the entire vast universe in a flash. Space is like a fabric which can be bent by masses and can be twisted and shaped. The gravitational field is determined by the equation g=(Gravitational Constant *Massobject)/(Radius)2 with G being the universal gravitation constant at approximately 6.67 * 10-11 Nm2/kg2 (the precision of this value is still being debated and is the worse known constant due to the regular weakness of the gravitational field. Once a mass attains a smaller radius such as a neutron star after a supernovae, according to the equation above, it’s gravitational field rises and soon enough is so great that it rips through space and time. If you could do this then you could travel between different points in the universe. However, it would take an enormous amount of energy to bend space( an example of this would be that the Schwarzchild radius(the radius at which an object becomes a black hole) of the earth is 0.9 centimeters. It is not known whether black holes lead to different points in the universe or not, but radio telescopes have picked up things called "white holes" which spew out trails of matter which could be the exit of a black hole. If you were to enter a black hole, it would rip you up into pieces and spit you out as if you are a piece of crap! Wormholes aren’t proven to exist unlike black holes which are proven by the General Theory of Relativity by Einstein. It is just another Star Trek "theory" which I strongly disbelieve. You might hear a Treakie say "Just because it can’t be seen, it doesn’t exist", right and the same applies to ghosts. Wormholes aren’t proven and at any point where space is bent there are enormous forces. You would need some technology to get through the fabric of time into subspace(if it exists). The space-time continuum is a concept associated with the theory of relativity, in which time is treated as a fourth dimension. It replaced the Newtonian concept of space and a separate, absolute time. In Newtonian mechanics, any event can be associated with a location in space described by three coordinates, usually x, y, and z, and a moment in time described by one coordinate, t. Although the coordinates chosen are arbitrary, two quantities are independent of that choice: the spatial distance between the two events, delta I, and the difference in time between the events, delta t. With the advent of relativity, however, it became clear that time depends on velocity and that delta I and delta t are no longer separately invariant. Delta I undergoes the Fitzgerald-Lorentz Contraction and delta t undergoes time dilation. A new quantity, delta s, is invariant instead. This quantity, known as the "line element" or "invariant interval," is related to the other quantities through a quadratic expression involving the speed of light. The quantity delta s is now the invariant measure of intervals between events, and the term metric (from the Greek word for "measure") often refers to the quadratic expression for delta ss. Hermann Minkowski developed (1908) the idea that a "space-time continuum" was the underlying "geometry" of special relativity and the Lorentz transformations, so that geometry is often referred to as "Minkowski space-time." In general relativity the space-time metric is more complicated and corresponds to curved space-time. If aliens were to visit us, they would have to warp space and that would be some technology to do something such as that. Also, why would aliens want to keep coming to earth and doing all these stupid things like probing cattle? Why wouldn’t they just make direct contact? The aliens are pretty much an invention of the entertainment industry and of writers and people themselves. Aliens probably haven’t made such contact to earth so that humans have noticed it, if they have it was unnoticeable. The way they could get here is through bending space as described above because the distances are so large and you can’t go faster than the speed of light according to the special theory of relativity(E=mc2). Aliens also probably wouldn’t want to come to earth because for what reason would they want to study the earth for? It all leads back to the question, "Are we alone?".
D2. Life could have been blown to earth inside a meteorite in the form of bacterial spores. There is evidence that meteorites are capable of carrying bacterial spores. There is an argument to whether or not the bacteria could survive the radiation and the effects of space. The modern-day bacteria wouldn’t be able to. This doesn’t prove anything because the earth has evolved and so have the bacteria. The old atmosphere of the earth contained methane, water vapor, ammonia, etc. The bacteria could have been capable of surviving the conditions of space and then evolved, because of the meteorite the bacteria wouldn’t burn up in the atmosphere. The galaxy is constantly moving through new space so the galaxy could have run into the meteorite which hit the earth. This is extraterrestrial origin. Chemical evolution might have happened already on an entirely different entity and then carried in a meteorite to earth. Organisms adapt to changes (evolution) so the bacteria could have too adapted. Bacteria then evolved into more complex forms.
The universe as a whole is awash with places where life might have arisen. Within our solar system, the tiny moon of Jupiter is the place most likely to support extraterrestrial life. In fact, conditions there would be far less hostile to life than the conditions that are thought to have existed in Earth’s primordial oceans. Our own Milky Way galaxy and the nearby Andromeda galaxy each contain more than 100 billion stars. And the universe holds more than a billion galaxies. Astronomers estimate that the universe contains some 1020 (100,000,000,000,000,000,000) stars with physical characteristics that resemble those of our sun. at least 10 percent of these stars are though to have planetary systems. New telescopes, such as the Hubbell Space Telescope, reveal that several nearby stars seem to have planets orbiting them. If only 1 in 10,000 of the planes in the universe has the right combination of mass and distance from its sun to duplicate Earth’s development, life could have arise 1015 ( a million billion) times. Undoubtedly, many other worlds have physical characteristics resembling those of Earth. Therefore, we might not be alone. Although, think of how scary it would be if we are, this whole huge vast universe and only one planet with life.
Life processes also might have arisen and evolved differently on other planets. A functional genetic system that is capable of accumulating and replicating changes is the basis of the evolution of life on Earth. But heredity does not require DNA – only a way to preserve and pass on information. Under different conditions, such a system theoretically could form substances other than the carbon-based compounds and water that make up life on Earth. Silicon and ammonia are the most likely possibilities. Like carbon, silicon needs four electrons to fill its outer energy level. And ammonia is even more polar than water. Perhaps under radically different temperatures and pressures, these substances might have formed complex molecules as diverse and flexible as the carbon-based ones on Earth.
