Initiation of life, the Universe, and everything

8/13/2019 Initiation of life, the Universe, and everything

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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
http://www.bibme.org/http://www.bibme.org/


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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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Initiation of life, the Universe, and everything