I. "The Changing Earth / Exploring Geology and Evolution - 2nd edition" by James S. Monroe & Reed Wicander; West/Wadsworth Pub. Co.; 1997
pg3 ... Earth from its
beginning 4.6 billion years ago ...
... the
first living cells evolving from a primordial organic
soup sometime betgween 4.6 and 3.5 billion years ago.
About 2 billion years later, cells with a nucleus evolved. Next (approx.
700 millions years ago), the first multicelled softbodied organisms evolved
in the oceans, then animals with skeletons, and then animals with backbones.
... an essentially bare landscape until about 450 million years ago
... Three interrelated themes ... The first is that Earth is composed of
a series of moving plates whose interactions have affected its physical
and biological history. The second is that Earth's biota has evolved.
The third is that the physical and biological changes that occurred took
place over long periods of time
... The second theme, the theory of organic evolution,
explains how life has changed through time, based on the idea that all
living organisms are the evolutionary descendants of lifeforms that existed
in the past. ... the third theme, the concept of geologic
time, allow geologists to show how small, almost imperceptible changes
over vast lengths of time have resulted in significant changes.
pg10 ... THE ORIGIN OF THE SOLAR SYSTEM ... According to the currently accepted theory for the origin of the solar system, interstellar material in a spiral arm of the Milky Way Galaxy condensed and began collapsing. ... The result was the birth of a star, our Sun. Some 4.6 billion years ago ... form the planet Earth.
pg11 ... Earth is a dynamic planet that has continuously changed during its 4.6-billion-year existence.
pg 12 ... In scientific usage, ... a THEORY is
a coherent explanation for one or several related NATURAL phenomena supported
by a large body of objective evidence. From a theory are derived
predictive statements that can be tested by observation and/or experiment
so that their validity can be assessed.
... Theories are formulated through the process known as the SCIENTIFIC
METHOD. This method is an orderly, logical approach that involves
gathering and analyzing the facts or data about the problem under consideration.
Tentative explanations or HYPOTHESES are then formulated to explain
the observed phenomena. Next the hypotheses are tested to see if
what they predicted actually occurs in a given situation. Finally,
if one of the hypotheses is found, after repeated tests, to explain the
phenomena, then that hypothesis is proposed as a theory. ... in science,
even a theory is still subject to further testing and refinement as
new data become available.
The fact that a scientific theory can be tested and is subject to such
testing separates science from other forms of human inquiry.
Because scientific theories can be tested, they have the potential of
being supported or even proven wrong. Accordingly, science must
proceed without any appeal to beliefs or supernatural explanations, not
because such beliefs or explanations are necessarily untrue, but because
we have no way to invesitigate them. For this reason, science makes
no claim about the existence or nonexistence of a supernatural or spiritual
realm.
pg18 ... ORGANIC EVOLUTION ...
The central thesis of organic evolution is that all present-day organisms
are related, and that they have descended with modifications from organisms
that lived during the past. ... Darwin proposed that NATURAL SELECTION,
which results in the survival to reproductive age of those organisms
best adapted to their environment, as the mechanism that accounts for
evolution.
... FOSSILS, ... not only provide evidence
that evolution has occurred, but also demonstrate that Earth has a
history extending beyond that recorded by humans. The succession
of fossils in the rock record provides geologists with a means for dating
rocks and allowed a relative geologic time scale to be constructed in the
1800s.
pg19 ... GEOLOGIC TIME SCALE,
resulted from the work of many nineteenth-century geologists who pieced
together information from numerous rock exposures and constructed a SEQUENTIAL
CHRONOLOGY based on changes in earth's biota through time. Subsequently,
with the discovery of radioactivity in 1895, and the development of various
radiometric dating techniques, geologists have been able to assign ABSOLUTE
AGE dates in years to the subdivisions of the geologic time scale.
EPOCHs(millions of years): Recent 0-.01
Pleistocent .01-2 Pliocene 2-5 Miocene
5-24 Oligocene 24-37 Eocene 37-58
Paleocene 58-66
PERIODs(m y): Cretaceous 66-144 Jurassic
144-208 Triassic 208-245 Permian 245-286
Pennsylvanian 286-320 Mississippian 320-360
Devonian 360-408 Silurian 408-438
Ordovician 438-505 Cambrian 505-570
EONs(m y)
Phanerozoic 0-570 Precambrian 570-4600 (.57 - 4.6 Billion
years)
pg 19 ... UNIFORMITARIANISM
... based on the premise that present-day processes have operated
throughout geologic time. ... allows us to use present-day processes
as the basis for interpreting the past and for predicting potential future
events. ... does not exclude such sudden or catastrophic events as
volcanic eruptions, earthquakes, landslides, or flooding. ... does not
require that the rates and intensities of geological processes be constant
through time. ...
What uniformitarianism means is that even though the rate and intensities
of geological processes have varied during the past, the physical and chemical
laws of nature have remained the same. ... the processes that
shaped it (earth) during the past are the same ones in operation today.
pg425 ... ABSOLUTE DATING METHODS ... tool
to date geologic events accurately, and thus verify the long time periods
postulated by Hutton, Lyell, Darwin
... RADIOACTIVE DECAY is the process whereby
an unstable atomic nucleus is spontaneously transformed into an atomic
nucleus of a different element.
pg426 ... HALF-LIFE ... is the time it takes for one-half of the atoms of the original unstable PARENT element to decay to atoms of a new more stable DAUGHTER element. The half-life of a given radioactive element is always constant and can be precisely measured.
pg427 ... By measuring the parent-daughter ration and knowing the half-life of the parent, ... geologists can calculate the age of a sample containing the radioactive element. ... The most accurate radiometric dates are obtained from igneous rocks. ... sedimentary rocks cannot be radiometrically dated ...
pg 430 ... To obtain accurate radiometric
dates, geologists must be sure that they are dealing with
a closed system, meaning that neither parent nor daughter
atoms have been added or removed from the system since crystallizatiion
and that the ratio between them results only from radioactive decay.
Otherwise, an inaccurate date will result. If daughter atoms have
leaked out of the mineral being analyzed, the calculated age will be too
young; if parent atoms have been removed, the calculated age will be too
great.
... To obtain an accurate radiometric date, geologists
must make sure that the sample is fresh and unweathered and that it has
not been subjected to high temperatures or intense pressures after crystallization.
... it is sometimes possible to cross-check the date obtained by measuring
the parent-daughter ratio of two different radioactive elements in the
same mineral. ... U 235 & U 238 ... If the minerals containing
both uranium isotopes have remained closed systems, the ages obtained from
each parent-daughter ratio should agree closely and therefore should indicate
the time of crystallization of the magma. If the ages do not closely
agree, other samples must be taken and ratios measured to see which, if
either, date is correct.
... The most commonly used isotope pairs are the
uranium-lead
and thorium-lead series, which are used principally to date
ancient igneous intrusives, LUNAR samples, and some METEORITES.
The rubidium-strontium pair is also used for very old samples
and has been effective in dating the oldest rocks on Earth as well as METEORITES.
The potassium-argon method is typically used for dating fine-grained
volcanic rocks from which individual crystals cannot be separated; hence
the whole rock is analyzed.
pg431 ... CARBON 14 DATING TECHNIQUE ... Carbon 14 has a half-life of 5,730 years ... technique is based on the ratio of carbon 14 to carbon 12 and is generally used to date one-living material. ... When an organism dies, carbon 14 is not replenished, and the ratio of C 14 to C 12 decreases as C 14 decays back to nitrogen ...
p433 ... DEVELOPMENT OF THE GEOLOGIC TIME SCALE ... is a hierarchical scale in which the 4.6-billion-year history of Earth is divided into time units of varying duration. It was not developed by any one individual, but rather evolved, primarily during the nineteenth century. ... a relative time scale because the rocks are arranged in their correct sequential order. ... By the beginning of the twentieth century (1900), geologists had developed a relative geologic time scale ... following the discovery of radioactivity near the end of the last century, radiometric dates were added to the relative geologic time scale. ... Thousands of absolute ages are now known for sedimentary rocks of known relative ages, and these absolute dates have been added to the relative time scale. In this way, geologist have been able to determine the absolute ages of the various geologic periods and to determine their durations.
p435 ... Absolute ages for rock samples are usually obtained by determining how many half-lives of a radioactive parent element have elapsed since the sample originally crystallized. ... The most accurate radiometric dates are obtained from longlived radioactive isotope pairs in igneous rocks. The most reliable dates are those obtained by using at least two different radioactive decay series in the same rock. ... Carbon 14 dating can be used only for organic matter such as wood, bones, and shells and is effective back to about 70,000 years ago.
pg440 ... BIOLOGICAL CONCEPT OF EVOLUTION, most appropriately called ORGANIC EVOLUTION, is concerned with inheritable changes in organisms. Evolution so defined is observable, at least on a small scale. For instance, the proportion of hereditary determinants in populations of moths in Great Britain changed so that their color changed from light to dark in several generations. LARGE-SCALE EVOLUTION is NOT directly observable but can be inferred from fossil evidence, and from studies of comparative anatomyu, embryology, and biochemistry of living organisms. ...
... The THEORY OF EVOLUTION
... The central claim of this theory
is that all present-day organixms are the evolutionary descendants of
life-forms that existed during the past. ... it is a naturalistic
explanation, and it can be tested so that its validity can be assessed.
...
... FOSSILS are the
remains or traces of prehistoric organisms that have been preserved in
rocks of the crust. In addition to their use in determining relative
ages of strata fossils are important in determining environments of deposition,
and they provide some of the evidence for evolution.
pg443 ... Darwin and Wallace proposed that
natural
selection is the mechanism to account for evolution. ... summarized
as following:
1. All populations contain heritable variations - size, speed, agility,
coloration, ...
2. Some variations are more favorable than others ...
3. Not all young survive to reproductive maturity.
4. Those with favorable variations are more likely to survive and pass
on their favorable variations.
pg446 ... PUNCTUATED EQUILIBRIUM, holds that a species changes little or not at all during most of its history and then evolves rapidly to give rise to a new species. ... long periods of equilibrium are occasionally punctuated by short periods of rapid evolution. ... Proponents of punctuated equilibrium claim that the fossil record supports their hypothesis. They argue that few examples of gradual transitions from one species to another are found in the fossil record, and that many species appear to have existed for millions of years without noticeable change. ...
pg 447 ... despite the incomplete nature of the fossil record, a number of examples of gradual transitions from ancestral to descendant species are known.
pg459 ... FOSSILS AND EVOLUTION ... The fossil record does show a sequence, but not one based on density, size, habitat, or shape of the fossils. Rather, it shows a sequence of appearances of different life-forms through time. The fact is that older and older fossiliferous rocks contain organisms increasingly different from those living today. One-celled organisms appeared before multicelled organisms, plants before animals, and invertebrates before vertebrates. Among the vertebrates fish evolved first, followed in order by amphibians, reptiles, mammals, and birds.
pg466 ORIGIN OF THE UNIVERSE
... Most scientists think that the universe originated between
15 and 20 billion years ago ... may be as
young as 8-12 billion years old ... in what is popularly called
the BIG BANG. In a region infinitely
smaller than an atom, both time and space were set at zero. As
explained by Einstein's theory of relativity, space and time are unalterably
linked to form a space-time continuum. .. without space there
can be no time. Therefore, there is no "before the Big Bang", only
what occurred after it. ...
... Two fundamental phenomena indicate that the Big
Bang occurred. The first is the expansion of the universe.
... Secondly, a background radiation of 2.7 deg K above absolute
zero permeates the entire universe. This background radiation is
thought to be the faint afterglow of the Big Bang.
... At the time of the Big Bang, matter as we know
it did not exist, and the universe consisted of pure energy. ... Matter
and antimatter collided and annihilated each other. Fortunately,
there was a slight excess of
matter left over that would become the universe.
pg467 ... After about 200 million years, as the universe continued expanding and cooling, stars and galaxies began forming and the chemical makeup of the universe changed
pg467 ... ORIGIN OF THE SOLAR SYSTEM ...
pg 469 ... the currently accepted solar nebula theory for the origin of the solar system involves the condensation and collapse of interstellar material in a spiral arm of the milky Way Galaxy. ... Within this solar nebula were localized eddies in which gas and solid particles condensed. Collisions between the various gases and particles resulted in accretion into planetesimals. As the planetesimals collided and grew in size and mass they eventually became planets. ... While the planets were accreting, material that had been pulled into the center of the nebula also condensed, collapsed, and was heated to several million degrees by gravitational compression. The result was the birth of a star, our Sun. ... The solar nebula theory of the formatiion of the solar system thus accounts for the similarities in orbits and rotation of the planets and their moons, the differences in composition between the terrestrial and Jovian planets, the slow rotation of the Sun, and the presence of the asteroid belt. Based on the available data, the solar nebula theory best explains the features of the solar system and provides a logical explanation for its evolutionary history. ...
... METEORITES are thought to be pieces of material that originated during the formation of the solar system 4.6 billion years ago.
pg483 ... Geologists know that Earth is 4.6 billion years old, the oldest known rocks, however, are 3.96-billion-year-old metamorphic rocks ...
pg485 ... The origin and earliest history of the MOON are still unclear ... It formed some 4.6 billion years ago ...