Earth’s History and the Origin of Life
I. Earth’s History
A. It is estimated that the age of the Earth is greater than ______________________ years.
B. One method of establishing the age of rocks and sediments on Earth is through
__________________________________________.
1. Many elements have ______________________.
Isotopes are atoms of the same:
2. Elements that are isotopes have the same ____________________________ (number of _______________),
but have different _________________________________. The atomic mass of an atom is the combined
number of __________________________________________.
3. Some isotopes are _______________________, and tend to undergo __________________________________.
This means that their nuclei tend to release particles, or energy, or both. These isotopes are
called _________________________________________.
4. The rate of decay for many isotopes has been determined. The amount of time it takes for
one-half of a sample of isotope to decay is called its ______________________.
5. The ___________ of a material can be determined by measuring the ________________ of a particular
radioactive isotope it contains.
C. Carbon-14 Dating
1. All living things take_____________ into their ____________ constantly. Most of this carbon exists in
a stable isotope known as _______________________. A very small portion of the carbon taken in
by living organisms is in the form of:
2. This ____________ of carbon-12 to carbon-14 that is taken in by all living organisms is a known
quantity.
3. When the organism __________, its uptake of carbon ______________. The amount of ________________
in the dead organism remains ___________________, but the _____________________ continues to
____________.
4. Over time, the amount of carbon-14 __________________ in comparison to the amount of carbon12.
5. The half-life of carbon-14 is ____________ years. When an organism has been dead for 5,730
years, only ________ of the carbon-14 remains in the ________________.
6. The age of the fossil can be determined by comparing the _________________________________________
in the fossil to the amount of _____________________________________ in the fossil.
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7. There are limits to carbon-14 dating due to the ________________________________ of carbon-14.
The use of carbon-14 dating is limited to organic remains ________________________________________.
D. Dating older rocks and sediments
1. In order to date rocks and sediments throughout Earth’s history:
2. Two isotopes are commonly used to date rocks and fossils that are very old.
a)
b)
3. Dating older fossils using these isotopes is challenging since:
4. Instead, scientists date _________________________________ by measuring the amounts of the
_____________________________________ found in each rock layer. If a fossil is then found in a
particular _____________, it can be assumed that the _____________ has an age relative to that rock
layer.
II. The Fossil Record Documents the History of Life
A. The fossil record provides glimpses of:
B. The fossil record shows that there have been great changes in the ___________________________________
that dominated life on Earth at different points in time. Many of the organisms of the past were
_____________________ today’s organisms. Many of the organisms that were once common on Earth
are now ______________________.
C. Fossils document how:
D. The fossil record is an incomplete record:
1. Many organisms of the past did not die:
2. Many fossils have been destroyed by:
3. Only a fraction of the fossils:
E. As a result, the known fossil record is biased in favor of species that:
1.
2.
2
3.
F. From the fossil record, scientists have established a geologic _________________ of Earth’s
________________. Now we will take a look at a few of the major events in Earth’s history.
III. The First Single-Celled Organisms
A. When the first organisms arose, there was little or no ____________________ in the atmosphere.
The first cells must have been ________________________.
B. The oldest microfossils indicate that these early cells were _____________________________. They
were most likely __________________________ that took in ____________________________________ from the
environment. At some point, the supply of these organic compounds would be __________________.
There would have been:
C. Early _________________________ were most likely __________________________.
In the process of chemosynthesis, ________________________________ is utilized as a source of carbon
for the building of ___________________________________.
The energy for this process comes from ________________________________________________________.
D. These ________________________________ were the only _________________________________________ from at
least 3.5 billion years ago to about 2.1 billion years ago.
E. The _________________________________ that are alive on Earth today may be similar to these early
_____________________________.
The archaebacteria thrive in extremely _________________________________ and many live in
__________________________ conditions.
IV. Photosynthesis and Aerobic Respiration
A. By 3 billion years ago, some cells had become ____________________________. These cells were able to
manufacture their own __________________________________________ using _____________ and the energy of
the ______________ to drive the chemical reactions.
B. A very damaging byproduct resulted in the form of ____________________.
This oxygen had an:
Oxygen inhibits the action of:
C. The rising levels of oxygen in the atmosphere that resulted from _________________________ probably:
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Some species survived in habitats that remained __________________________.
D. Other species ______________________ to the changing environment. One such adaptation was
__________________________________, which uses _________________ in the process of
______________________________________ from organic compounds.
E. The first cells capable of carrying out photosynthesis were probably:
F. It took over a _______________________ years for the _________________ levels to reach today’s levels. As
oxygen reached the upper atmosphere, it was bombarded with ____________________. Certain
wavelengths of sunlight can split ________ to form highly reactive _____________________________________.
These react with _________ to form ________________________. The ozone in the upper atmosphere
forms a protective layer that absorbs ____________________________________________, and prevents most
of it from reaching Earth’s surface. UV radiation damages __________.
Without this important ozone layer:
V. The First Eukaryotes
A. Remember that eukaryotic cells differ from prokaryotic cells.
1. Eukaryotic cells are:
2. Eukaryotic DNA is organized into:
3. Eukaryotic cells contain:
4. Eukaryotes have a:
B. How did these eukaryotic cells develop?
1. Between 2.0 and 1.5 billion years ago, a type of small ___________________________________ entered
and began to live and reproduce inside ________________________________________________________.
2. What may have started as an ____________________ of one cell by another cell became a very
_______________________ and ________________________________________ relationship.
3. This theory is known as _____________________________. The aerobic prokaryote eventually gave
rise to:
C. A second invasion
1. Sometime later, there was a second successful invasion of pre-eukaryotic cells. This time the
invader was a relatively modern ____________________________________________. These invaders gave
rise to:
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D. The Evidence
1. Both mitochondria and chloroplasts _________________________________________________ within the
cells that contain them.
2. Chloroplasts and mitochondria contain their own ___________.
This DNA is different from the DNA found in the _________________of the cell. The DNA consists
of a:
3. Chloroplasts and mitochondria contain their own _______________________, and so can carry out
their own __________________________________. These ribosomes are more similar to prokaryotic
ribosomes than they are to eukaryotic ribosomes.
4. Both chloroplasts and mitochondria have inner ________________________ that contain
__________________ and transport systems that are the same as those found in the plasma
membrane of living prokaryotes.
VI. The First Multicellular Eukaryotes
A. After the first eukaryotic cells appeared, a great diversity of ___________________________________________
evolved. This tremendous diversity in the eukaryotic, unicellular world continues today.
B. Some __________________________ eukaryotes gave rise to _________________________________ forms whose
descendants include ________________________________________________________________.
C. The oldest known fossils of multicellular eukaryotes are of small ________________ that lived about
1.2 billion years ago.
D. Larger and more diverse multicellular organisms do not appear in the fossil record until about
___________________________________ years ago.
E. Roughly 535 to 525 million years ago, a phenomenon occurred called the
______________________________________.
1. During the early Cambrian period (535-525 million years ago), many phyla of _________________
suddenly appear.
2. Prior to this period, the fossil record shows the presence of at least three animal phyla:
a)
b)
c)
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3. All of the animals in these early animal phyla were ______________________________, and the fossils
show little to no evidence of _________________________. These early animals appear to have been:
4. This soon changed during the Cambrian explosion.
5. In a short period of time (10 million years), _____________________ emerged that had _____________
for capturing prey and defensive adaptations such as:
VII. The Colonization of Land
A. The _____________________________________________________ began to colonize landmasses around 500
million years ago.
B. This required adaptations to solve two problems:
1.
2.
C. The land plants of today show the solutions to these problems.
1. Land plants contain:
2. Land plants are also equipped with a:
3. The true land plants deliver:
Water is no longer needed to accommodate a swimming sperm.
D. Adaptations seen in early animal groups that colonize the land include:
1.
2. The ___________________________________ of the reptiles. The amniote egg is an egg with a
___________.
This egg can be:
VIII. Life on Earth is Influenced by Large-Scale Processes
A. Life on Earth has a seen a rise and fall of many groups of organisms. The changes to life on
Earth are influenced by large-scale processes such as:
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1.
2.
3.
B. Continental Drift
1. The continents we live on move over time.
2. There have been ______________ occasions in Earth’s history in which all of the landmasses of
Earth came together to form a:
It is estimated that the continents will come together again and form a
____________________________________ roughly 250 million years from now.
3. This “continental drift” has a major impact on life on Earth.
4. As the continents drift, the ________________________ of living organisms are altered. Shallow
lakes and seas may dry up, and other areas may become much wetter.
5. As the continents drift:
C. Mass Extinctions
1. The fossil record shows that the majority of living organisms that ever lived are now
______________________.
2. A species may become extinct when its habitat is ______________________ or its environment
_______________________ in a manner that is _____________________________ to the species.
3. A mass extinction occurs when:
4. ________________ mass extinctions are documented in the fossil record.
5. More than a thousand species have become extinct in the last 400 years. Scientists are
questioning whether a sixth mass extinction is under way.
D. Adaptive Radiations
1. Adaptive radiations are periods of evolutionary change in which groups of organisms form
many new ____________________.
These “new” organisms have adaptations that allow them to fill
__________________________________________________ in their communities.
2. Large scale adaptive radiations have occurred ________________________________________________.
A mass extinction leaves:
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