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Initiation of life, the Universe, and everything
Emily S. Moore
Abstract
Life on Earth is exceptionally serendipitous when considering all that is required for life to form;
such as mass, the Earth and moon, magnetic field via formation of a differentiated core, the
atmosphere, plate tectonics, and most importantly liquid water. The purpose of this paper is to
lightly discuss necessary components to life, present relevant discussion of how life is theorized
to have initiated on Earth, and briefly observe the evolution of life throughout Earth sHistory;
including the expansion of the universe, evolution of complex-multicellular life, moderate to
devastating extinctions of life and the re-diversification of organisms, filling abandoned niches in
the biome.
Cosmogony and the Earth; a foundation for life
Spontaneous aggregation of mass
Life on Earth involves a great number of variables coming together within appropriate
time and space. Primarily the universe must form; researchers theorize every atom in the
universe can be traced to a single point. The rapid expansion from that point is commonly known
as the Big Bang Theory(McClendon, 1999, 75).Initially the universe was much less than the
size of an atom and consisted of pure energy. Expansion occurred within seconds and continues
to expand (less rapidly) so that the edges of the universe are the oldest. Edwin Hubble observed
that other galaxies are moving away from earth at a rate proportional to their distance from us.
After expansion began, subatomic particles formed. Hydrogen and Helium were the first
elements to form; all other elements were subsequently formed through cooling, collision,
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rotation and contraction of gases (Wayne, 1992, 382). The rotation and contraction of gases
allowed stars and galaxies to form by about 1 billion years. When stars contract fusion and
warming occur; in some circumstances this leads to an explosion that gives birth to a supernova,
which further fuses elements. Accretions of these elements lead to mass, accretion of mass can
give way to the formation of planetary bodies that fall into orbit in the gravitational field of a
supernova.
Earth accreted from dust sized particles to meter scale particles and so on. As Earth
accumulated it heated through collision and pressure energies (accretionary heat) and radioactive
decay (Wayne, 1992, 383). Iron (thought to have been deposited by asteroids) collapsed
gravitationally to form the core, as iron and silicates cannot become homogeneous. Once the
inner core began gyrating, the added circulation of the liquid-iron outer core generated earths
magnetic field. The magnetic field is imperative for life on Earth, as it deflects solar winds,
keeping volatiles and the atmosphere in place. Plate tectonics are a product of Earths rotating
interior help to stabilize the biosphere. The moon is also necessary for life on earth to begin. It
formed during the Heavy Bombardment Period (or a period of intensecomet andasteroid
bombardment) by a glancing blow to Earth that caused a considerable amount of mass to enter
Earthsgravitational field. The mass then re-accreted either to back to earth or to itself. The
material that accreted together formed the moon (McClendon, 1999, 71). The gravitational
relationship between the earth and the moon produces tidal patterns and provides an umbrella
from asteroids; supported by the heavily cratered dark side of the Moon. Life emerged around
3.8-3.5 billion years, just after the end of the asteroid showers; this is derived through the
geologic record of fossils.
http://www.bbc.co.uk/science/space/solarsystem/other_solar_system_bodies/comethttp://www.bbc.co.uk/science/space/solarsystem/other_solar_system_bodies/asteroidhttp://www.bbc.co.uk/science/space/solarsystem/other_solar_system_bodies/asteroidhttp://www.bbc.co.uk/science/space/solarsystem/other_solar_system_bodies/comet -
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Liquid H2O is absolutely imperative for life and occurs only in the Goldilocks zone as
low temperatures cause water to freeze and too hot of temperatures causes water to vaporize.
Earth is also the right size: too small cannot hold atmosphere in place, too large, the atmosphere
becomes too dense for sunlight to penetrate (Brack, 1999, 418). Over time atmospheric water
vapor increased; borne by comets entering the atmosphere. Cooling then prompted the
development of a primitive hydrologic cycle and very long periods of rain. Earths early
atmosphere was largely carbon dioxide (CO2), water vapor (H2O), methane (CH4), ammonia
(NH3), and hydrogen chloride (HCl). These gases occurred from out-gassing of numerous active
volcanoes and vents, also through degassing by vaporization of Earth rocks due to asteroid
impact (McClendon, 1999, 76).
The missing step: genesis and evolution of living cells from inorganic compounds
There are several theories that help to explain the origin of life and how organisms have
evolved over time. The Miller-Urey experiments are the most popular and cited to explaining
how life on Earth began. The experiment used H2O, CH4, NH3, and hydrogen (H2) (the
chemicals present in Earths early atmosphere)to form glycine, hydrogen cyanide (HCN), and an
oily material (Lazcano et al., 2003, 236).The chemicals were sealed inside a array of sterile glass
flasks and flasks connected in a loop, with one flask half-full of liquid water and another flask
containing a pair of electrodes. (See Figure 1)The liquid water was heated to induce evaporation,
sparks were fired between the electrodes to simulate lightning through the atmosphere and water
vapor, and then the atmosphere was cooled again so that the water could condense and trickle
back into the first flask in a continuous cycle. By this process, they were able to created amino
acids or what could have been building blocks of life. Microspheres of these proteins may have
fused to begin forming DNA and RNA to become primitive cells. Amino acids break down
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Figure 1: Simplified diagram of the assemblage and procedure of the Miller-Urey Experiment
Note. From Miller-Urey ExperimentMcGraw-Hill Online Learning Center Test, 2013, Online
Source.
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under prolonged exposure to UV Radiation so prominent theories conclude that life likely
evolved from single-celled organisms to multi-cellular organisms in tidal pools or tidally
influenced areas. Some speculation focuses on the oily byproduct of the experiments. The matter
could have helped to protect primitive life from lethal amounts of radiation as well as act as a
base for the condensation of polymers. However, there is no hard evidence to derive exactly
when or how living cells developed from non-living chemicals (Bada, 2004, 3).
Other theories explaining the origin of life include: extraterrestrial sources
(comets/asteroids), organic compounds in the atmosphere, or the ocean. The impact of
extraterrestrial material would likely cause destruction of potential life-kindling amino acids;
however it is possible some amino acids could have been delivered. Most researchers accept that
life originated along mid ocean ridges where hydrothermal vents spew superheated water
sulphides, and a variety of minerals dissolved from basaltic rock (but do not reject other theories).
Additionally, there are a wide range of temperatures and an abundance of elements and minerals
surrounding hydrothermal vents and volcanic chimneys (McClendon, 1999, 80). Modern
microbes (known as hyperthermophiles) thrive in the extreme conditions within the vents. The
microbes perform chemosynthesis, or the oxidization of sulfide and methane, providing a basis
for a food chain. Bacteria near hydrothermal vents metabolize hydrogen sulfide (H2S) and
produce energy, sugars, and sulfur (Campbell, 2006, 362). Chemistry favorable for
chemosynthesis produces H2, CH4, NH3; proteins that were replicated in the Miller-Urey
experiments (Campbell, 2006, 362). (See Figure 2). Life may have developed here
autotrophically and evolved into heterotrophic organisms in shallow tidal waters; or developed a
very early distillation of metabolism (McCleddon, 1999, 81).
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Figure2:Schematicdiagramdepictingamid-oceanridgehydrothermalventsite
andpotentialmicrobialhabitatsin
thesub-seafloor.
Note.FromSievertLabforMicrobialEcolog
y&PhysiologybyJackCook,20
12,OnlineSource.
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Record of the establishment and evolution of life
The oldest indications of life are fossils of primitive prokaryotic microbial organisms
more than 3.5 billion years old (Levin, 2013, 159). Single celled fossils and stromatalites
(mound shaped cyanobacteria commonly known as an alga that is similar to modern
photosynthetic bacteria) are the oldest unequivocal evidence of life. There are 3.6 billion-year-
old rocks containing chemical and microscopic evidence for life, however they are not
widespread or abundant (McClendon, 1999, 72). Some researchers believe life could have
originated multiple times, but survived only once. There have been several well-documented
mass extinctions, some more extensive than others, in spite of this life since 2.2 billion years has
never truly wiped out. This is based on genetic similarities through Earths time and spaceand
evidence in the rock record (McClendon, 1999, 85). (See Figure 3).
Fossils (fragments of organisms, preserved by casting, replacement, permineralization
and/or carbonization) and trace fossils (tracks, trails etc) serve as an ancient record of
evolution through time (Schopf et al., 2007, 151). Records of marine life are far more extensive
than that of land. This is due to the abundance of marine life in Earths history;also that many
land organisms fall prey to scavengers and chemical weathering after death and are rarely buried
fast enough for quality preservation. Fossil spores and pollen grains help to provide additional
evidence of paleoenvironments and the evolution of plant life. The fossil record is sufficient
enough to derive the life and habits of early organisms and provide clues to Earths changing
paleoenvironment. Paleogeography can be identified by index fossils (fossils that are wide-
spread geographically, and abundant for a short span of geologic time). Index fossils aid in
recreating Earths paleoenvironments. The paleoenvironment of the Earth is intimately related to
the evolution of organisms; this pairing is better known as paleoecology. Paleoecologists often
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Figure3:
Basicstepsintheoroginoflife.
Note.FromEvolutionFigures:Chapter4,F
igure4.4,2013,OnlineSource
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use features and habits of modern organisms to help determine those of ancient organisms.
Physical features can also help determine past climates; from attributes such as thick shells to the
size of fossils can help to determine the climate of an ancient environment.
Progression of unicellular prokaryotic cells to modern complex life-forms
Development during the Precambrian
The Archean Eon (4.6-2.5 Ga) it holds almost 80% of Earths recorded geologic history.
(See Figure 4) By the end of the Archean Eon, the Earth had developed a differentiated core,
magnetic field, moon, primitive plate tectonics and hydrologic cycle; and life as we know it can
begin to develop. The Archean Eon saw an atmosphere rich in carbon dioxide, and a notable lack
of carbonate deposition (the combination of carbon dioxide and water form carbonic acid,
keeping alkaline rocks from forming) (Levin, 2013, 231). By the late Archean, oxygen was
increased by photo-disassociation, or intense bombardment of ultra-violet radiation, of
atmospheric water molecules driving water vapor to dissociate hydrogen atoms from oxygen
atoms (Wayne, 1992, 387). After the advent of life, photosynthesis plays a major role in
oxygenating the atmosphere (McClendon, 1999, 75).
Anaerobic prokaryotic organisms were the first life forms to develop. Photoautotrophs
(photosynthetic cyanobacteria and floating prokaryotes) were abundant during the Archean (3.5-
3.8 Ga) yielding a gradual change in atmosphere to include oxygen (Schopf et al., 2007, 143).
This permitted other oxygen-intolerant organisms, such as heterotrophs and anaerobic organisms,
to adjust to the atmosphere. Once oxygen became prevalent in Earths atmosphere, the ozone(O3)
began to form, protecting organisms from radiation and distributing life into shallower
environments (Wayne, 1992, 391). Apex chert is extensively studied for its well established
cellular, filamentous microfossils (McClendon, 1999, 72). Life for almost two billion years was
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Figure 4: Simplified Geologic Time Scale, encompassing the origin and evolution of life
Note. From The Archaeology News Network, 2013, Online Source.
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prokaryotic and genetically restricted. Evidence of multicellular life first appears about 2.2 Ga;
some biologists suggest that independent microorganisms entered other cells in a symbiotic
relationship causing organelles to develop and forming multicellular life. By beginning of the
Proterozoic, molecular fossils of eukaryotes appear but are few and far between.
The early Proterozoic Eon or Paleoproterozoic (2.5 Ga- 542 Ma) was similar to the
Archean, single-celled organisms are extremely abundant. Stromatolites (large mat-like
sedimentary structures) became extremely abundant and played a large role in oxygenating the
atmosphere. Gunflint Chert (1.9 Ga) holds excellent record of Proterozoic microbial life. Life
emerges multicellular and abundant in the late Proterozoic, or Neoproterozoic, and truly begins
to diversify around one billion years. The evolution of metazoans or Ediacaran Biota
(multicellular animals that are organized into tissues and organs) occurred by the end of the
Proterozoic (Levin, 2013, 266).
Once eukaryotes (organisms with a membrane-bound nucleus) began reproducing
sexually, genetic variation increased, leading to the diversification of phyla. These organisms
show the first true signs of adaptations and branching out; organisms present during this eon
includejellyfish, soft corals, sponges, early mollusks, organisms with calcareous shells and
tube-dwelling worms. Proterozoic organisms remain mostly soft-bodied attributed to lack of
predators in Earths early environment(Schopf, 1989, 446). Plants had begun to evolve during
the Precambrian; the development of said plants helped to oxygenate the atmosphere and is
imperative to the evolution of terrestrial life; primarily for production of oxygen but also as a
food source for the organisms.
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Development during the Phanerozoic
Ecological alterations and extinctions during the Paleozoic
The Cambrian Period (540 Ma- 485Ma) is famous for its explosion of life; markedly
trilobites and brachiopods become abundant, jawless fishes develop, and the foundations for all
modern phyla were laid (Wayne, 1992, 391).Organisms with hard shells (that protect and support
organs) came onto the scene and are often well-preserved in the fossil record due to the resistant
shells. Vennier (2009) suggests it is the introduction of visionthat was the main trigger of the
ecological turnover (e.g. antipredatorial responses from prey such as [an]exoskeleton).
Burgess Shale is famous for its remarkable preservation of organisms during the Cambrian
Period; organisms such as condonts, sponges, crinoids, corals, chordates and many others that
were previously unknown (Harper, 2006, 150).
Life during the Ordovician Period (485 Ma-443 Ma) was notable for its large increase in
biodiversification, and by the Late Ordovician, substantial reef-building. This can be accredited
to a large amount of seafloor spreading which results in extensive shallow nutrient-rich seas
(Harper, 2006, 157). Plant life (largely semi- aquatic, spore-bearing) began to colonize land but
remained primitive and low-lying. The end of the Ordovician experienced a mass extinction of
many marine families and reef-builders; it is the second largest extinction in Earths history.
Surviving species were those that coped with the changing conditions and filled the ecological
niches left by the extinctions.
The Silurian Period (443 Ma- 419 Ma) underwent a rapid shift from icehouse to a period
of runaway warming after the Late Ordovician extinction. The evolution of land plants helped
stabilize rates of erosion and increase nutrient cycling (Burgoyne et al., 2005, 19-20). Jawless
fishes flourish and jawed fish appeared by the late Silurian. Warmer temperatures allowed plants
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to thrive and develop vascular stems and root systems by the late Silurian. Significant
developments during the Devonian Period (419 Ma- 358 Ma) include the return and
diversification of reefs, the appearance of insects and amphibians, and an increase in complexity
and abundance of jawed fished. Plants were undergoing enormous evolutionary-changes
throughout the Devonian Period; and by the Late Devonian large trees and forests evolve with
the development of seeds as a mode of reproduction (Alegeo et al., 1998, 116). The late
Devonian experienced a moderate extinction (mostly affecting reef builders) credited to
eutrophication. Alegeo (1998) summarizes, arborescenceresulted in a transient intensification
of pedogenesisenhanced chemical weathering that may have led to increased riverine nutrient
fluxes that promoted development of eutrophic conditions. Long-term effects included
drawdown of atmospheric CO2leading to a brief Late Devonian glaciation.
Carboniferous (358 Ma-298 Ma) and Permian (298 Ma-252 Ma) Periods experienced the
longest plateau of ecological stability. The most significant development in the Pennsylvanian
Period is the evolution of reptiles with the ability to reproduce on land (Waggoner et al., 1996).
Organisms and vegetation continue to thrive until the end of the Permian Period. Life on earth
was nearly eliminated in the greatest extinction in Earths history. The extinction occurred in two
stages over a few thousand years with multiple contributing factors. The most influential factor is
volcanic activity that spewed tons of basaltic lava (known as Siberian Traps) into the biosphere.
A dramatic decrease in oxygen isotope levels lead to global warming and a reduction of ocean
circulation; this created an oxygen-poor environment in the oceans (Benton et al., 2003, 360-2)
escalating the extinction.
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Ecological alterations and extinctions during the Mesozoic & Cenozoic
Organisms during the Triassic Period (250 Ma-200 Ma) recover from the devastating
annihilation and modern-type coral evolve. Terrestrial animals re-diversified, filling abandoned
niches in the biome. Advent of mammals and dinosaurs occur around the late Triassic, with the
addition of birds in the late Jurassic (Brusatte et al., 2010, 70). The Jurassic (201 Ma- 145Ma)
and the Cretaceous Periods (145Ma- 65 Ma) were rather uneventful: Pangaea gradually split
apart, and biodiversification of genera increased. The extinction of the dinosaurs marks the K/T
(Cretaceous/Tertiary [Cenozoic Periods]) Boundary (Waggoner et al., 1996). Most researchers
agree that the extinction was triggered by asteroid impact supported by iridium abnormalities and
clay deposits. Wallis (2007, 304-6) theorizes microfungi that flourished after the K/T
transitiontipped the balance from dinosaurs to mammals. The K/T extinction had a large
impact on terrestrial life, but minimum impact on marine ecosystems.
The Paleogene (66 Ma-23 Ma) is notable for the return of reefs and the co-evolution of
grass and hooved herbivores; by the late Paleogene organisms that survived the K /T extinction
have adapted and are similar to modern organisms. After extinction of the dinosaurs, diversity of
mammals continues to increase (most were small and lived underground so they could weather
the storm), imbuing the niche left by the dinosaurs. The early Neogene (23 Ma- 2.5 Ma) &
Quaternary (2.5Ma-Present) Periods witness the evolution of whales and more importantly
primates appear and begin evolution to hominids and intelligent life (Briggs et al., 2008, 121).
Conclusion
Fossils extending back to the Archean support evolution from unicellular life to
multicellular life; eukaryotes and the development of sexual reproduction ushered in genetic
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variation and subsequently diversification of organisms consistently throughout Earths history.
As seen in extinction patterns through the Paleogene Period, when organisms rapidly disappear
from the environment the ecosystem can rebound towards equilibrium too fast, causing a further
imbalance on the planet (and, consequently, a slower return to stability); or organisms that
survived the extinction event will swiftly diversify and exploit the available evolutionary niche
vacated by the preceding organisms (Benton, 2001, 221). While five major mass extinctions have
ensued between the Ordovician to the Late Cretaceous Period, life was never completely
eliminated and progressed in tandem with the progression of flora. In conclusion: through
escalation of random collisions and accretion of matter, life spontaneously arose from the
ignition of inorganic compounds and proteins, developing membranes of carbon, oxygen,
proteins, and hydrogen. These collections of elements are held together in a fragile sack molded
around a meat-coated skeleton, which is presently hurtling around a supernova at roughly sixty-
seven thousand miles per hour. Everything, life, and the universe, formed from the expansion of
a single atom.
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