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IMPORTANT TERMS:
¾ prokaryote = bacteria; cells that do not possess a cell nucleus or membrane bound
organelles; first cells to evolve on Earth about 3.8 to 3.5 billion years ago; these cells are
smaller (about 10 microns) than eukaryotic cells.
¾ eukaryote = all non-bacterial life on earth; an organism made of cells that possess a cell
nucleus and membrane bound organelles; evolved later on Earth about 1.7 to 1.5 billion
years ago; these cells are larger (about 100 to 400 microns) than prokaryotic cells.
¾ autotroph = an organism that makes its own food.
¾ heterotroph = an organism that eats other organisms in order to obtain nutrients and
energy’.
FIVE KINGDOMS OF LIFE (developed by Robert Whittaker in 1969)
Kingdom Monera = the kingdom into which bacteria or prokaryotes are classified. Members of
this kingdom (prokaryotes) have a simple cellular structure with no cell nucleus and no
membrane bound organelles (e.g. mitochondria, Golgi apparatus, etc). Bacteria can be
photoautotrophs with chloroplasts for photosynthesis (eg. cyanobacteria) or they can be
chemoautotrophs that make food using inorganic molecules without sunlight (such as at
hydrothermal vents in the ocean). Bacteria may or may not be mobile via a prokaryotic
flagellum (bacterial flagella have a very different molecular structure compared to
eukaryotic flagella).
Kingdom Protoctista (formerly Kingdom Protista) = the kingdom into which unicellular
eukaryotes (and closely related colonial organisms) called protists are classified. Members
of this kingdom are the simplest eukaryotic organisms (their cells have a nucleus and
contain a variety of cell organelles). The “animal cell-like” protozoa are protists. Protists
can move using a variety of structures such as cilia, flagella or pseudopodia. They can be
autotrophs, heterotrophs or both.
Kingdom Fungi = the kingdom into which the fungi are classified. Molds, yeast, and
mushrooms are examples. Fungi are multicellular eukaryotic heterotrophs that digest their
food externally (outside their bodies) and absorb the small nutrient molecules that result
(that is, fungi are decomposers). Fungi are important decomposers that break down dead
organisms into simpler biological molecules that can be recycled in the environment. Fungi
develop from spores.
Kingdom Plantae = the kingdom into which the plants are classified. Plants are multicellular
eukaryotic autotrophs (usually non-mobile). Plants develop from an embryo.
Kingdom Animalia = the kingdom into which the animals are classified. Animals are
multicellular eukaryotic heterotrophs that are usually mobile (although not always) and
digest their food internally. Animals develop from a blastula.
Spontaneous Generation
A once widely held (now thoroughly and obviously falsified) theory that living organisms could
spontaneously arise from nonliving material. This doctrine was first confronted by
Francesco Redi in 1668, when he noted that covered jars of meat did not create maggots.
However, it was not until the 1860s that fermentation experiments by Abbe Lazzara
Spallanzani and Louis Pasteur provided evidence that fully dismissed the theory of
spontaneous generation.
The Big Bang – The beginning of the universe – both space and time?
In 1927, the Belgian priest Georges Lemaitre was the first to propose that the universe began
with the explosion of a primeval atom. His proposal came after observing the red shift in
distant nebulas by astronomers to a model of the universe based on relativity. Years later,
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Edwin Hubble found experimental evidence (at the Mount Wilson Observatory in Southern
California) to help justify Lemaitre’s theory. He found that distant galaxies in every direction
are going away from us with speed proportional to their distance. 15 billion years ago (+/- 5
billion years) the entirety of the known universe was compressed into the confines of an atomic
nucleus known as a singularity. This is the moment before space and time existed. According
to the prevailing cosmological models that explain our universe, an incredible explosion, trillion
of degrees in temperature, that was infinitely dense, created not only fundamental subatomic
particles and thus matter and energy, but both space and time.
The Red Shift
The Doppler Effect as it occurs for light. The Doppler Effect refers to a change in frequency due
to the motion of the source (as in when the sound of a passing car changes as the car passes
the listener). When a light source approaches, there is an increase in its measured frequency;
and when it recedes, there is a decrease in its frequency. An increase in frequency is called a
blue shift, because the increase is toward the high frequency or blue end of the electromagnetic
spectrum. A decrease in frequency is called a red shift, referring to a shift toward the lowerfrequency, or red, end of the color spectrum. Distant galaxies, for example, show a red shift in
the light they emit. A measurement of this shift permits a calculation of their speeds of
recession as the universe expands.
Cosmological theory suggests that at about 10 - 43 second
after the big bang the four forces of nature:
1. Strong nuclear force
2. Weak nuclear force
3. Electromagnetism
4. Gravity
were combined into a single force and did not become separate forces until later…
The Four Fundamental Forces of Nature in the Universe
Strong Nuclear Force = the attractive force that holds the atomic nucleus together. The
strong interaction occurs between protons, neutrons and mesons, but only acts over very short
distances (10-15 meter).
Weak Nuclear Force = the force responsible for beta (electron) emission. The weak nuclear
force moderates certain kinds of nuclear decays and commonly involves particles called
neutrinos.
Electromagnetism = the magnetic forces produced by electricity; refers to the various waves of
the electromagnetic spectrum.
Gravity = the attraction between any two objects which have mass (the reason objects “fall” to
Earth).
The Big Bang Model and the Beginning of the Solar System
Based on the Big Bang Model, the universe originated from an expanding mass of proto-matter
that has been expanding since the beginning of time 13 to 18 billion years ago. During the
early stages of the Big Bang, atoms did not yet exist. As the proto-matter (plasma) cooled,
quarks (the building blocks of protons and neutrons) fused to form atomic nuclei and the
simplest atoms (e.g. hydrogen and helium). As the universe continued its expansion,
cooling clouds of hydrogen gas could now condense to form the first stars. Further fusion
within the largest of stars (red and blue giants) gave rise to atoms with larger atomic nuclei
(more protons). Our sun, Sol, and the eight (plus Pluto as a dwarf planet) recognized
planets formed about 4.6 billion years ago out of a spherical cloud of rapidly spinning
cosmic dust and gases. The fusion reactions that created the sun began as the dust
collapsed under its own gravitational pull. The residual material left behind condensed
further to form the planets.
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EARTH – SOME STATS
¾ ORBIT: 149,600,000 km (from Sun)
¾ DIAMETER: 12,756.3 km
¾ DAY (Rotation): 24 hours
¾ ATMOSPHERIC PRESSURE: 760 mm Hg at sea level
¾ ATMOSPHERE: 77% Nitrogen, 21% oxygen, 0.03% carbon dioxide, traces of water and
argon
¾ 4.5 to 4.6 billion years old
¾ 71% of the surface is covered by water; heat capacity of oceans helps keep Earth’s
temperature relatively stable; causes most erosion and weathering (a unique process in
the Solar System, although it may have happened on Mars in the past)
¾ Modest Magnetic Field
¾ Interaction of Earth and Moon slows Earth’s rotation about 2 milliseconds per year.
Current research indicates that about 900 million years ago there were 481, 18 hour
days per year.
LAYERS OF THE EARTH’S CRUST
EARTH’S CRUST & CORE
Depths in km:
¾ 0-40
CRUST
¾ 40-400
UPPER MANTLE
¾ 400-650
TRANSITION REGION
¾ 650-2700
LOWER MANTLE
¾ 2700-2890
DEEP MANTLE
¾ 2890-5150
OUTER CORE
¾ 5150-6378
INNER CORE (mostly iron)
¾ CORE TEMPERATURE = 7500 K (hotter than the Sun)
The Early Atmosphere of Earth
Early Earth was heavily bombarded by large comets and meteors which would have vaporized
any oceans present. About 3.8 billion years ago, near the end of the heavy bombardment,
Earth’s atmosphere was primarily composed of carbon dioxide and nitrogen with smaller
amounts of carbon monoxide, hydrogen and sulfur. Virtually no oxygen was present in the
primeval atmosphere. So, oxidation did not occur easily as it does today (e.g. aerobic cell
respiration could not occur).
The Oparin-Haldane Hypothesis
In the 1920s, Alexander Oparin (a Russian biochemist) and J.B.S. Haldane (a British biologist)
independently theorized that life originated on Earth after a very long period of molecular
evolution. This hypothesis states that Earth’s early, primitive atmosphere lacked oxygen,
but consisted of simple compounds such as water, carbon dioxide, methane and ammonia.
Ultraviolet (UV) radiation bombardment of the primitive earth was much more intense as
there was no ozone layer to protect the Earth from UV rays. When this mix of compounds
was exposed to ultra-violet radiation and/or lightning, the mixture of gases formed many
simple organic (carbon containing) substances such as sugars and amino acids (some of
the building blocks of life). Haldane believed that these organic molecules accumulated to
form a primordial soup of carbohydrates, simple fats, proteins and nucleic acids that could
eventually assemble into the earliest and simplest microorganisms (bacteria). Finally, in
1953, Stanley Miller and Harold Urey successfully simulated the conditions of early Earth
with a laboratory apparatus that produced surprisingly high levels of biomolecules.
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Stanley Miller
In 1953, Miller was the first scientist to show that amino acids and other organic molecules
could have been generated on a lifeless Earth. Miller performed experiments to support the
Oparin-Haldane hypothesis. Subsequently, similar experiments by many scientists have
verified his results.
Potential Sources Of Energy For Molecular Evolution:
¾ Ultraviolet Rays from the Sun
¾ Electrical Discharges (Lightning)
¾ Volcanic Activity
¾ Hydrothermal Vents on Sea Floor
ribozyme = an RNA molecule (a molecule similar to DNA) that can speed up chemical reactions
and copy itself. Many biologists now believe that RNA emerged before DNA and that RNA
catalyzed the early chemical reactions that led to the formation of more complex molecules.
These complex molecules could then have associated together and interacted to form
simple cells.
The First Cells and the Theory of Endosymbiosis
Based on fossil evidence, the earliest cells appear to have been prokaryotes (bacteria).
Biologists generally now believe that eukaryotic cells evolved from prokaryotic cells
according to the endosymbiotic theory. This theory suggests that present-day eukaryotic
cells evolved from the combining of several different types of primitive prokaryotic cells. It is
thought that some organelles found in eukaryotic cells may have originated as free-living
prokaryotes. Mitochondria and chloroplasts contain bacteria-like DNA and they can control
their own duplication, it has been suggested that they originated as free-living bacteria.
These bacterial cells could have established a symbiotic relationship with another primitive,
nucleus containing cell to form the first eukaryotic cells. Further invagination of the cell
membrane could have led to the evolution of the rough and smooth endoplasmic reticula.
The Origin of the Eukaryotic Cell via the Theory of Endosymbiosis
The modern eukaryotic cell arose from an ancestral prokaryote. Probable steps included loss of
the cell wall and inward folding of the plasma membrane. This was a process by which the
mitochondria and chloroplasts of eukaryotic cells probably evolved from symbiotic associations
between small prokaryotic cells living inside larger ones. An infolded cell membrane attached
to the chromosome may have led to formation of a nuclear envelope. A primitive cytoskeleton
evolved. The first truly eukaryotic cell was larger than its prokaryote ancestor, and possibly
possessed one or more eukaryotic type flagella.
Prokaryotic cells incorporated as
endosymbionts gave rise to eukaryotic organelles. Peroxisomes may have been the first
organelles of endosymbiotic origin. Mitochondria evolved from proteobacteria, chloroplasts from
cyanobacteria. Cells with nuclei probably appeared before those with mitochondria.
¾ Endo = “in”
¾ Symbiosis = a close association between organisms of two different species
Earth’s Atmosphere Today
Presently, Earth’s atmosphere contains about 77% nitrogen, 21% oxygen, 1% argon and 0.03%
carbon dioxide which makes the atmosphere oxidizing. Photosynthesis, by plants,
cyanobacteria and phytoplankton in the ocean, is the main source of atmospheric oxygen.
Most of the oxygen in the atmosphere is probably derived from the phytoplankton and
cyanobacteria in the oceans (the oceans cover more than 70% of the surface of the Earth).
At any point in time, nearly all the oxygen produced is consumed by organisms for cellular
respiration. Thus, the oxygen rich environment we experience today is the result of
the evolution of a biological process = photosynthesis.
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aerobic cell respiration = the production of cellular energy (ATP) by cells from organic
compounds such as sugars and fats using oxygen. Oxygen is required for aerobic cell
respiration.
anaerobic cell respiration = the production of cellular energy by cells from organic
compounds such as sugars and fats without using oxygen. Oxygen is not required for
aerobic cell respiration.
photosynthesis = the trapping of energy from the sun by chlorophyll containing cells (plants,
cynaobacteria, phytoplankton) and the conversion of that energy into a form that the cell
can use (3-phosphoglycerate) for the synthesis of carbohydrates (e.g. sugars such as
glucose) from carbon dioxide and water.
cyanobacteria (“blue-green algae”) = photosynthetic, oxygen producing bacteria that were
formerly called blue-green algae. Cyanobacteria and prokaryotes appear to have been the
dominant life forms on Earth for the first 2 billion years of its existence. They were among
the first cells to evolve the process of photosynthesis.
chemoautotroph = an organism that obtains both energy and carbon from inorganic
molecules. These organisms make their own organic compounds from carbon dioxide
without using light energy. Chemoautotrophs do not perform photosynthesis, they use
special inorganic compounds (such as hydrogen sulfide) as an energy source. A few species
of deep-sea marine bacteria (thermophiles such as Thermus aquaticus) living near
hydrothermal vents in the oceans are chemoautotrophs. These specialized bacteria provide
the base for entire food chains of organisms that live at the bottom of the ocean where there
is no sunlight (and thus no photosynthesis).
THREE DOMAINS OF LIFE (first developed by Carl Woese in 1990)
The Bacteria (or Prokarya) = The “typical”, modern bacteria. These bacteria are found in
virtually every ecological niche on the planet except very extreme environments. This
domain includes the clinically important bacteria as well as the nitrifying soil bacteria.
The Archaea = The most ancient bacteria, like the most ancient archaea, may be
thermophiles, suggesting that life originated in a hot environment. The domain Archaea
can be divided into two kingdoms: Crenarchaeota and Euryarchaeota. Crenarchaeota are
heat-loving and often acid-loving archaea. Methanogens produce methane by reducing
carbon dioxide. Some live in the guts of herbivorous animals; some in high-temperature
environments on the ocean floor. Extreme halophiles are salt lovers that lend a pinkish
color to salty environments; some grow in extremely alkaline environments.
The Eukarya = All of the organisms on earth made of eukaryotic cells. All non-bacterial life.
Choanoflagellida – similar to the sponges
The Choanoflagellida are protists with flagella and a body type similar to a characteristic type
of sponge cell. The Choanoflagellida are sister to the animal kingdom. See the colonial
flagellate hypothesis in the text and the Phylum Porifera lab regarding the evolution of the
metazoan animals.
Once the planet formed and life evolved, large scale geologic events greatly affect
biogeography.
biogeography = the geographical distribution of species.
continental drift = a change in the position of continents resulting from the incessant slow
movement (floating) of the plates of Earth’s crust on the underlying molten mantle. The
mantle constantly undergoes convection as cooler molten rock near the surface loses heat
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to space and falls to the center of the Earth, while warmer molten rock near the Earth’s
center rises. It has caused continents to periodically fuse and break apart throughout
geological history. As the plates drift, this could affect the biogeography (distribution and
evolution) of different species of organisms on Earth (e.g. the lungfish).
plate tectonics = forces within planet Earth that cause movements of the crust, resulting in
continental drift, volcanoes and earthquakes.
Pangaea = the supercontinent consisting of all the major landmasses of Earth fused together.
Continental drift formed Pangaea near the end of the Paleozoic Era about 250 million years
ago. Since then continental drift has separated Pangaea into the seven separate continents
we have today.
-- For your information – details below will not be on an exam -A GENERALIZED REVIEW OF BIG BANG THEORY…
An estimated 13.7 billion years ago, the entirety of our universe was compressed into the
confines of an atomic nucleus. Known as a singularity, this is the moment before creation
when space and time did not exist. According to the prevailing cosmological models that
explain our universe, an ineffable explosion, trillions of degrees in temperature on any
measurement scale, that was infinitely dense, created not only fundamental subatomic
particles and thus matter and energy but space and time itself. Cosmology theorists combined
with the observations of their astronomy colleagues have been able to reconstruct the
primordial chronology of events known as the big bang.
Quantum theory suggests that moments after the explosion at 10-43 second, the four forces of
nature; strong nuclear, weak nuclear, electromagnetic and gravity were combined as a single
"super force" (Wald). Elementary particles known as quarks begin to bond in trios, forming
photons, positrons and neutrinos and were created along with their antiparticles. There are
minuscule amounts of protons and neutrons at this stage; approximately 1 for every one billion
photons, neutrinos or electrons (Maffei). The density of the Universe in its first moment of life is
thought to have been 1094grams/cm3 with the majority of this being radiation. For each billion
pairs of these heavy particles (hadrons) that were created, one was spared annihilation due to
particle-antiparticle collisions. The remaining particles constitute the majority of our universe
today (Novikov).
During this creation and annihilation of particles the universe was undergoing a rate of
expansion many times the speed of light. Known as the inflationary epoch, the universe in less
than one thousandth of a second doubled in size at least one hundred times, from an atomic
nucleus to 1035 meters in width. An isotropic inflation of our Universe ends at 10-35 second that
was almost perfectly smooth. If it were not for a slight fluctuation in the density distribution of
matter, theorists contend, galaxies would have been unable to form (Parker).
The universe at this point was an ionized plasma where matter and radiation were inseparable.
Additionally there were equal amounts of particles and antiparticles. The ratio of neutrons and
protons albeit small is equal. When the universe aged to one hundredth of a second old
neutrons begin to decay on a massive scale. This allows for free electrons and protons to
combine with other particles. Eventually the remaining neutrons combine with protons to form
heavy hydrogen (deuterium). These deuterium nuclei combine in pairs and form helium nuclei.
The formation of matter from energy is made possible by photons materializing into baryons
and antibaryons with their subsequent annihilations transforming them into pure energy
(Maffei). Because of these collisions and annihilations matter was unable to remain viable for
more than a few nanoseconds before a bombardment of electrons would scatter these photons.
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Like water trapped inside a sponge, radiation is so dense (1014g/cm3) that no light is visible.
Known as the "Epoch of Last Scattering" the temperature has now dropped to a mere 1013K
with the Strong Nuclear, Weak Nuclear and Electromagnetic interactions now able to exert
their force (Chown).
As the gas cloud expands one full second after the initial explosion and the temperature of our
Universe has dropped to ten billion degrees, photons no longer have the energy to disrupt the
creation of matter as well as transform energy into matter. After three minutes and a
temperature of one billion degrees, protons and neutrons were slowing down enough in order
to allow nucleosynthesis to take place. Atomic nuclei of helium were produced as two protons
and neutrons each bonded. For every helium nucleus formed there were about ten protons left
over allowing for twenty-five percent of the Universe to be comprised of helium. The next
important phase of the expansion occurred around thirty minutes later when the creation of
photons increased through the annihilation of electron-positron pairs. The fact that the
universe began with slightly more electrons than positrons has insured that our Universe was
able to form the way it has (Parker).
The universe for the next 300,000 years will then begin to expand and cool to a temperature of
10,000°K. These conditions allowed for helium nuclei to absorb free floating electrons and form
helium atoms. Meanwhile hydrogen atoms were bonding together and forming lithium. It is
here that the density of the universe has expanded to the point where light can be perceived.
Until this point photons continued to be trapped within matter. Finally the expansion allowed
for light and matter to go there separate ways as radiation becomes less and less dense. Matter
and radiation therefore too, were bonded no longer and the oldest fossils in the Universe were
born (Peebles).
In 1814 the science of spectroscopy was launched by William Wollaston, an English physicist
who noticed that there were several dark lines that separated the continuous spectrum of the
Sun. These lines came to the attention of Joseph von Fraunhofer, a German optician and
physicist who carefully plotted the position of those lines. Then in 1850 German physicist's
Gustav Kirchhoff and Robert Bunsen refined the spectroscope. They then learned to heat
different elements to incandescence and using the spectroscope identified an element’s
corresponding lines on the visible portion of the electromagnetic spectrum (Parker).
In 1863 Sir William Huggins, an amateur astronomer viewed a nearby star through his 8 inch
refractor with a spectroscope attached. He found what he had originally hypothesized, the
same spectrum lines that were observed in our own Sun. Meanwhile, Kirchhoff and Bunsen
had successfully categorized the spectrum lines of many elements including those of hydrogen,
sodium and magnesium. Huggins found these same spectrum lines in the distant stars he had
observed and correctly predicted that some of the same elements that Kirchhoff and Bunsen
were cataloging were emanating from these celestial bodies (Parker).
Christian Doppler of Austria discovered twenty years earlier that the frequency of a sound wave
was dependent on the relative position of the source of the sound. As a sound moves away from
an observer the pitch will lower. Likewise if the source is not moving but the observer is, there
will be a corresponding change in the wave frequency of the sound. Doppler theorized on this
same shift for light waves yet it was the French physicist Armand Fizeau who proved in 1848
that when a celestial object moves away from an observer, the lines in the visible spectrum
would shift toward the red end. Conversely, when an object moves toward the observer, Fizeau
found that the lines in the spectrum shifted toward the blue end. Huggins observed a shift in
the hydrogen lines of Sirius toward the red end of the spectrum. This "redshift" indicated that
Sirius was moving away from us. A few years later he was able to calculate the radial velocity of
the star Sirius at between 26 to 36 miles per second (Parker).
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During the 1890's the Lick Observatory in California began to track and chart the radial
velocity (which is actually the velocity at which the line of sight that the star is observed) of
many stars, as well as gaseous and planetary nebulae. Astronomers at Lick calculated the
measurements of 400 stars including their radial speed and velocity. In 1910 Vesto Slipher
measured the velocity of the Andromeda Nebula at 300 km per second, thirty times greater
than previously observed. Four years later, Slipher had confirmed the radial velocities of 14
spiral nebula, with the overwhelming majority shifting to the red end of the spectrum. Slipper's
observations showed that the majority of spirals he measured were moving away from us
(Parker).
Around 1913 several astronomers, among them Edwin Hubble, used a variable star known as
a Cepheid (a star that fluctuates in intensity) to measure their period-luminosity relationship.
This would accurately determine the distance to any Cepheid in the observable vicinity. Hubble
became the first astronomer to discover an independent galaxy outside the confines of the
Milky Way. Hubble calculated the distance of the Andromeda Galaxy to be 900,000 light years
away; larger than the predicted size of our own galaxy. Using the radial velocity measurements
of Slipher along with Hubble's own calculations he began to notice a correlation between the
distance of these galaxies and their radial velocities. The proof was conclusive: the further away
a galaxy was relative to the Earth, the greater the velocity of that galaxy. Hubble had
irrefutable proof that the Universe was expanding. By 1936 Hubble had received data from
galaxies more than 100 million light years away. The redshifts at this distance were so large
that the spectral lines had changed color (Weinberg).
As astronomers were collecting data on the Universe based on their observations, theorists
were busy developing models that attempted to explain the cosmos. Recently equipped with
Albert Einstein’s Theory of Relativity, Einstein was one of the first to attempt an explanation of
the physical Universe. Einstein believed the Universe to have a static, uniform, isotropic
distribution of matter. Einstein's own calculations however proved to result in the exact
opposite, an oscillating universe that had the potential for expansion or contraction. He was
certain that the universe was stable. Einstein was compelled to amend his original equation.
He used the term cosmological constant, which created a spherical, four-dimensional closed
universe (Parker).
Around the same time the Dutch astronomer Willem deSitter used Einstein's general theory of
relativity to develop his own model of the Universe. His model was unique in that it did not take
into consideration the existence of matter in the Universe. However it did go beyond Einstein's
model in that it predicted the redshift, even though de Sitter felt it was an illusion, and did not
at the time link it to any recession of celestial objects. The academic community of 1930 did
not fully embrace either model of the universe. Then the Secretary of the Royal Astronomical
Society in England was made aware that three years previous, one of his students had written
a theory of the universe independent of the two major forces in cosmological theory. Georges
Lemaître created a cosmology that predicted a universe that was forever in a state of
expansion. When this theory was rejuvenated by its republication in the journal Monthly
Notices, it brought to the table another similar theory that was devised ten years earlier.
Aleksander Friedmann, a Russian mathematician, analyzed Einstein's cosmological constant
that produced a static universe. Friedmann proved that there are three possibilities for the
universe when the cosmological constant is zero. If the matter in the universe is greater than
the critical density, the universe would ultimately collapse back onto itself. If the inverse is
correct the universe would expand forever. If the universe were flat with a constant of zero at
critical density, the universe would again expand infinitely. Both Lemaître and Friedmann's
solutions were analyzed by Einstein and were summarily dismissed. It was not until Hubble
had proved that galaxies were in fact receding in 1932 that Einstein was forced to drop his
static universe model. The observational proof that the universe was expanding, combined with
the models of Friedmann and Lemaître that predicted an expanding universe unified the
cosmologist and the astronomer in agreement. The only question remained was if the universe
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is expanding, what was the origination of this expansion? Lemaître used the second law of
thermodynamics as his starting point. Based on the assumption that the expansion of the
universe was an increase in the disorder of a system, originating from a singularity of
neutrons, this primordial nucleus would then explode where an increase in the entropy of the
universe would be apparent. On May 9, 1931, Lemaître published his theory of the universe in
the journal Nature and it was met with general skepticism (Parker).
George Gamow expounded on Lemaître's work, using recent discoveries in quantum theory.
Lemaître formulated his model based on the theory that a giant nucleus began to entropy,
breaking down into individual constituents. Gamow believed that a nucleus containing not only
neutrons but protons and electrons as well was the starting point. Due to the very high amount
of radiant energy in the early universe, temperature would be in excess of one billion degrees
Kelvin. At five minutes old, Gamow speculated, this universe would have particles that could
not combine. But as the expansion began the temperatures would decrease and nuclear fusion
would occur. Atoms would form as protons and neutrons would attach themselves to one
another. Gamow then Hypothesized that all the elements in the Universe were created at this
time. One year later however, it was proven that Gamow's math didn't stand up to scrutiny as
it was shown that atomic mass 5 could not have been created from this primordial nucleus, as
well as mass 8 (Gribbin).
Although all of the elements in the universe were proven not to have originated from the
Primordial Fireball, the theory gained momentum until it received a worthy adversarial
cosmology known as the Steady State Theory. Fred Hoyle (who despairingly coined the term Big
Bang) and his colleagues constructed a model of the universe that was widely accepted for
religious reasons if not so much for its scientific hypothesis. Hoyle suggested that the universe
is infinitely old and has remained in a steady state except that the universe was indeed
expanding. However galaxies are not receding from one another but space is constantly being
created between galaxies. In order for the average density to remain constant, Hoyle suggested
that matter had to be created in these new areas where space was expanding. Only one
hydrogen atom needed to be created every year in an area the size of a 100 meter cube to
account for the expansion. This spontaneous generation of matter Hoyle argues would allow for
the formation of new galaxies between ancient ones and the Universe would maintain its steady
state. It would then follow that astronomers would be able to detect young galaxies in the
midst's of very old ones. This was one of the many inconsistencies that were found with the
Steady State Theory. In the 1950's Steady State Theorists took a heavy blow when radio
galaxies were discovered showing that, consistent with big bang Cosmology, galaxies evolved
and were very active billions of years ago (Parker).
Finally the empirical evidence big bangers had predicted was observed in 1965 by Bell Labs
Arno Penzias and Robert Wilson. Robert Dicke of Princeton University was the first to search
for fossil remains of the big bang. Dicke suggested that the Big bang emanated from a previous
universe and that a temperature in excess of one billion degrees was necessary to create our
new universe. This energy would in turn produce an infinitesimal amount of radiation that
should be measurable to this day. Planck's law states that all bodies emit energy that can be
documented on an electromagnetic diagram. Depending on the length of the wave they can
register anywhere from X rays to radio waves and everything in between. A body’s emission of
energy is contingent upon the constituent elements of the body, the amount of surface area of
the body and the surface temperature of the body. The body that emits the greatest amount of
energy is a so called black body. Using Planck's Black Body Curve as a guide Dicke theorized
that the Cosmic Background Radiation of the Big Bang should be about 3° above absolute zero.
Dicke's colleague Jim Peebles also concluded that when the Fireball's remnants cooled to
3000° Kelvin nuclei would be able to form and helium was able to form from hydrogen. This left
a universe with a mixture of approximately 75% hydrogen and 25% helium, resembling the
same amount of helium found in the Sun. Peebles concluded that since the two most abundant
elements in the universe were created when the Universe was at 3000° K and since then the
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universe has expanded by a factor of 1000 the radiation from the Big Bang should have a
temperature of about 10° K. Later refinements to these equations revised the estimated
temperature to 3° K. Dicke and Peebles were confident that there instruments would be the
first to detect this Cosmic Background Radiation (Parker). At the same time Penzias and Wilson
were busy attempting to measure radiation from the Milky Way Galaxy. They were narrowing in
on their source when they were left with a noise that was interfering with their signal. This
noise originated from cosmic radiation and had a temperature of 3°K. It seemed to be coming in
from all directions and never fluctuated. With their original research corrupted due to the
unexplained noise they resigned themselves to writing a paper on this unexplainable
phenomenon. Months later Penzia's discovered that Peebles group was searching for this relic
radiation without success. Upon further examination they realized that Penzia and Wilson had
stumbled upon the single most important discovery that confirmed the Primordial big bang
Explosion(Parker).
Big Bang theorists made several predictions that have eventually supported the theory. The
first is Hubble's observation of the redshift-distance relationship. This relationship enables us
to approximate the age of the universe with the help of three separate celestial bodies that all
arrive at the same relative result. Hubble used what is known as "standard candles" to build a
"cosmic distance ladder." By knowing the distance of certain celestial bodies he would be able
to incrementally construct an age for the Universe. These standard candles were: cepheid
variables in neighborhood galaxies; bright stars in more distant galaxies and in galaxies
millions of parsecs away, the brightness of the galaxy itself was used as a standard candle
(Maffei)
Central to the question of the age of the Universe are two important theoretical terms. The
Hubble Constant refers to how fast the velocities of the galaxies increase with their distance
from the Earth. There is quite a raging debate on the value of this constant ranging from 50
Km/sec per Mpc (Mpc is a Megaparsec, about 3 million light years) to 100 Km/sec per Mpc.
This explains the disparity in the ± 5 billion year estimates for the age of the universe. The
other constant of importance is known as q that defines the deceleration of the expansion of
the universe. Depending on the critical density of the universe that this q constant is based,
the universe will prove to be either infinitely expanding as in the flat and open models, or an
oscillating closed universe; a big crunch/big bang universe that will ultimately condense back
into a singularity and begin the process all over again(Weinberg). Hubble's successor Allan
Sandage predicted a closed universe when he plotted a number of radio galaxies many billions
of light years away. The evidence for this closed universe was quickly challenged a few years
later and eventually fell out of favor. To this day the Hubble Constant and the q constant
remain the two most important unanswered problems in modern cosmology.
Observations have also supported the predictions of theorists that certain elements could only
have been created moments after the big bang. Based on the relationship between the amount
of helium in the universe and the number of different types of particle "families" researchers
concluded that there is one neutrino per family of particles. Due to the current energy density
of the universe there will be a corresponding amount of helium produced. This in turn will
create different types of neutrinos. When the predicted amount of neutrinos corresponded to
what was observed it was another victory for the big bang cosmology (Wald).
After the discovery of the cosmic background radiation in 1965 scientists were eager to extend
their research into outer space through the use of a man-made satellite orbiting the Earth.
From this vantage point an unimpeded opportunity to study this phenomenon would be made
available and by late 1989 the Cosmic Background Explorer (COBE) was ready for action.
COBE consisted of three separate experiments. The first instrument was known as the FIRAS,
an acronym for the Far Infrared Absolute Spectrometer. This instrument was created to
confirm the research previously accumulated that the background radiation does indeed have a
black body spectrum (Hoverstein).
The Origin and Early Evolution of Life on Earth
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Biological Sciences 102 – Animal Biology – Notes & Vocabulary
The next question COBE attempted to answer was, is the background radiation the same
temperature in all directions? Big bang theory states that in order to have mass condense and
form galaxies, there must be in homogeneities left over from the Big bang that will be able to be
detectable. The differential microwave radiometer (DMR) was designed to detect anisotropy
fluctuations on the scale of 30 millionths of a degree. Inflation theory predicted such
fluctuations and that quantum processes at work during the primordial stages of the big bang
(when the universe was the size of a proton) allowed for clouds of matter to condense into
galaxies (Sawyer).
The final experiment was known as DIRBE. The Differential Infrared Background Experiment
was designed to look into the farthest corners of the Universe; upwards of 15 billion light years
away from the Earth, and accumulate data on the infrared light of these primordial galaxies.
DIRBE data is continuing to be accumulated with no conclusions having been drawn to date
(Gribbin). John Mather from the University of California at Berkeley was responsible for the
FIRAS experiment. Not long after COBE was positioned into orbit came the exciting data that
was eagerly awaited and much anticipated. The background radiation fit the blackbody curve
to within 1%. Sixty-seven separate points of frequency obtained by COBE fir the theoretical
blackbody spectrum perfectly! Observation had accurately confirmed what Big bang cosmology
had long ago predicted. This finding proved to be the easy part (Parker).
George Smoot and his colleagues also from Cal Berkeley took three arduous years to sort
through the billions of bits of data that the DMR provided. His announcement on the 23rd of
April, 1992 at the annual meeting of the American Physical Society in Washington, D.C. said it
best: "English doesn’t have enough superlatives...to convey the story [of the results], we have
observed...15 billion year old fossils that we think were created at the birth of the universe."
(Parker). Although the temperature fluctuations were less than thirty millionths of a degree in
variation, these areas of temperature and density fluctuation were more than 500 million light
years in width. These miniscule perturbations that were formed during the big bang were the
very density that was needed in order to create galaxies and thus life itself (Noble).
References
Chown, Marcus, Birth of the Universe, New Scientist, February 26, 1994, v141, n1914, pA1(4).
Chown, Marcus, All You Ever Wanted To Know About the Big Bang, New Scientist, April 17,
1993, v138, n1869, p32(2)
Gribbin, John R., In Search of the Big Bang: Quantum Physics and Cosmology, Toronto; New
York: Bantam Books, 1986.
Hoversten, Paul, Relics of Universe's Birth Found, USA Today, April 24, 1992, Col A, 1:4.
Maffei, Paolo, The Universe in Time, Cambridge, MA: The MIT Press, 1989.
Noble, John Wilford, New York Times, Big Bang Ripples Observed, February 1, 1994, Col 6:4.
Novikov, I.D., Evolution of the Universe, Cambridge, U.K. : Cambridge University Press, 1983.
Parker, Barry R., The Vindication of the Big Bang: Breakthroughs and Barriers, New York:
Plenum Press, 1993.
Peebles, James P., The Evolution of the Universe, Scientific American, October 1994, v271, n4,
p52(6).
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Biological Sciences 102 – Animal Biology – Notes & Vocabulary
Sawyer, Kathy, New Findings Support Theory of "Big Bang", Washington Post, April 24, 1992,
Col A, 1:4.
Wald, Robert M., Space, Time and Gravity: the Theory of the Big Bang and Black Holes, 2nd
Edition. Chicago: University of Chicago, 1992.
Weinberg, Steven, The First Three Minutes: A Modern View of the Origin of the Universe, New
York: Basic Books, 1977.