GenBio2 - Q3 Module 2 For Grade 12 Mendel
GenBio2 - Q3 Module 2 For Grade 12 Mendel
GenBio2 - Q3 Module 2 For Grade 12 Mendel
General Biology 2
Quarter 3-Module 2:
History of Life on Earth
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General Biology 2 – Grade 12
Quarter 3– Module 2: History of Life on Earth
Second Edition, 2021
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MODULE 2
History of Life on Earth
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Directions: Write the letter of the correct answer on a separate sheet of paper.
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Introduction: Geology and the Geologic Time Scale
The science that deals with studying the Earth—its materials and
processes is known as geology. Modern geology began in late 1700s when James
Hutton introduced the Principle of Uniformitarianism, which became the
fundamental principle of geology today. The principle states that forces and
processes that can be observed shaping the Earth at present, have been at work
for a long time since the Earth’s beginnings. Many of the important contributions
in the advancement of geology began with the study of rocks and its layering
(strata). Ancient rocks have unlocked various types of evidences of ancient lives
that have been hidden for millions, even billions of years. Today, scientists like
geologists, paleontologists (scientist who study fossils), chemists, and biologists
have worked together to analyze the physical, chemical, and biological materials
in ancient rocks. Geologists use the principles of relative dating and the
principle of fossil (remains of dead organisms) succession in determining the
age of rocks, which became the start of the development of the geologic timescale,
a scale that can place rock evidence into specific time interval and recreate the
events of the past to the present time. These methods were limited at comparing
the relative age (older vs younger) of the layers of rocks and comparing rock
layers with layers from other locations.
Let us review
Direction: Answer the following items on a separate sheet of paper.
1. Differentiate the following terms:
a) Geology vs Paleontology-__________________________________________
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The Geologic Time Scale
The geologic time scale divides the history of the Earth into time intervals
which are: eons, eras, periods, and epochs. The longest time interval is eon
which can be subdivided into smaller intervals called eras, and eras can be
divided into periods, and periods into much smaller intervals called epochs. The
geologic time scale gets the formal names based on rock evidence (which may
include fossils and other chemical evidence) that is date specific. The
International Committee on Stratigraphy (ICS), a committee of the
International Union of Geological Sciences are responsible for determining and
formalizing the time intervals of the Geologic Time Scale.
The Phanerozoic eon is the time interval that began 541 million years ago
(mya) and is derived from Greek words meaning “visible life”, which is
appropriate as this eon represents a large collection of evidences of diverse life
forms that showed major evolutionary transitions.
2.Arrange the following time intervals from the longest (4) to the shortest (1)
time interval.
a) Eon _____
b) Epoch _____
c) Era _____
d) Period _____
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Lesson 1: The Precambrian Supereon
Archean eon
The Archean eon is said to be the time when first signs of life began. The
oldest rock known is found in an area of Greenland called the Isua formation
which is about 3.85 billion years old. These rocks contain quartz crystals that
preserved organic deposits of carbon isotopes which are found in organisms.
This finding showed a glimpse of the first simple organisms that lived in this
eon. They did not use oxygen but used organic molecules that formed near the
end of the Hadean eon, which became sources of carbon and energy. Carbon
dioxide was also said to be abundant in the atmosphere during the Archean eon.
Then, after millions of years, organisms started to evolve and utilize light energy
and atmospheric CO2 for photosynthesis. These organisms were known as
photosynthetic bacteria and archea, thus, the term Archean eon for the
dominant groups of bacteria (classified as prokaryotes) that are able to survive
in extreme environment.
Proterozoic eon
After the prokaryotes dominated the archean eon, the rise of the
eukaryotes (unicellular organisms with true nucleus) followed. Fossil evidence
show that eukaryotes emerged about 1.9 to 1.4 bya. Recorded fossils from
Australia dated 1.69 byo are chemically similar to eukaryotic membranes. The
evolution of eukaryotes can be explained in the Endosymbiotic Theory
proposed by Lynn Margulis.
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that shaped the Earth. The events that we have been experiencing at present are
similar events that have shaped the Earth in the past, these are important events
that have allowed organisms to evolve. While many became extinct during these
events, it paved the way for new organisms to flourish.
Did you know that the suffix -zoic found in the names of the events in the
geologic time scale refer to animal life forms? This means that animal life forms
were dominant during these events.
The geologic time scale is divided into the Precambrian supereon and the
Phanerozoic eon.
Directions: Fill in the names of the events in the figure below. Write your
answers on a separate sheet of paper.
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The Phanerozoic eon is the more recent eon and is subdivided into eras
which include Paleozoic era, Mesozoic era, and Cenozoic era (shown in figure
2.3). These eras are further subdivided into periods and the most recent periods
are subdivided into shorter time intervals called epochs. Phanerozoic is derived
from the Greek word that means “visible life” which is appropriate as this eon
represents the widest collection of small to large fossils from different organisms
that show evolutionary transitions which are found in rock layers dated from
541 mya to present.
In the following section, we will know more about the subdivisions of the
phanerozoic eon.
Cambrian Period
This period is also known as “Cambrian explosion” as fossils of major
groups of animals diversified within a few million years of each other. Most
important fossils were from organisms with hard parts including the insect-like
trilobites, nautiloids, scorpion-like eurypterids, and brachiopods, which looked
like clams. Many of these invertebrates were identified only as “small, shelly
fossils” and coexisted with the abundant red and green algae, sponges,
jellyfishes, and worms which were found in the Cambrian seas.
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Ordovician Period
Fossil evidence of the first vertebrates, jawless fishes called ostracoderms,
appeared during this period. Fossil evidence also showed that spore-forming
primitive plants (resembled nonvascular plants today) may have moved to land.
The Ordovician period ended with a large-scale mass extinction of marine
invertebrates.
Silurian Period
The first plants with water-conducting and mineral conducting tissues
known as vascular plants evolved at this time. The first land animals also left
fossil evidence which looked like scorpions which were predators of smaller
animals. Fungi are said to have also colonized land. Aquatic animals also
continued to diversify which is very common after a mass extinction event.
Varied forms of fishes (jawless and jawed) lived in freshwater and marine
environments, the oceans were rich in corals, trilobites and mollusks.
Devonian Period
This period is known as the “age of fishes” as more fishes diversified as
bony and cartilaginous fishes. By the end of the period, the first amphibian
appeared which resembled fishes but with paddlelike legs and toes. Mass
extinction of marine organisms ended the Devonian period, although many land-
dwelling organisms, such as the highly diversified plants, were mostly not
affected.
Carboniferous Period
This period is known as the “age of amphibians” as more amphibians
dominated both land and water. The carboniferous period is subdivided into two
epochs, namely (oldest to more recent): Mississippian and Pennsylvanian.
Many land plants like ferns and early seed plants and many different kinds of
insects dominated the Carboniferous (meaning “coal bearing”) period. By the end
of the period, many of these plants died which were buried beneath swamps
which formed the rich coal layers of the Earth, which is the source of the fossil
fuel (coal) that we have today.
Permian Period
During this period, gymnosperms (non-flower bearing plants) became
dominant while reptiles were the dominant animals including the ancestors of
dinosaurs. The Permian period ended with the most catastrophic mass
extinctions, also known as “the mother of mass extinctions,” as it affected 90%
of species, which were mostly marine invertebrates found in shallow areas of the
seas.
Mesozoic Era (“Age of Reptiles”)—252-66 mya
The Mesozoic was dominated by small and huge reptiles called the
dinosaurs. This era is subdivided into three periods, namely: Triassic, Jurassic,
and Cretaceous periods (shown in figure 2.5).
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Figure 2.5. Geologic Time Scale- Mesozoic Era
Triassic Period
The ancestors of the now-extinct dinosaurs called the archosaurs
increased during this period paving the way of the “age of reptiles”. The ancestors
of mammals called therapsids also appeared and coexisted with the reptiles in
the forested lands. Forests were mainly dominated by gymnosperms such as
cycads, ginkgos, and conifers. Another mass extinction occurred by the end of
the Triassic period affecting smaller reptiles, amphibians, and marine animals.
The larger, more adapted reptiles dominated the land which included the
dinosaurs.
Jurassic Period
This period is known as the “age of dinosaurs” as this was dominated by
them. Both herbivorous and carnivorous reptiles dominated the land, including
large marine crocodiles, the ancestors of birds (Archeopteryx) and dinosaurs. The
first flowering plants (angiosperms) appeared during this period, but forests were
still dominated by gymnosperms. The first frogs and the first true mammals,
which were the size of rats, appeared at this time.
Cretaceous Period
Huge diversification of organisms both plants and animals occurred at this
time. Flowering plants diversified so fast, and many insects also appeared.
Reptiles hunting other groups of animals and even those of their own was very
common at this time. The Cretaceous period ended with the mass extinction of
75% of species including the large reptiles, the dinosaurs, and thus, ending the
Mesozoic era. The mass extinction cleared the way for the dominance of smaller
organisms that survived the asteroid impact (said to be the cause of the mass
extinction) which included the birds, amphibians, and mammals.
Paleogene Period
Subdivided into three epochs:
• Paleocene epoch—early placental mammals appeared including
the first primates, speciation of birds and insects.
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• Eocene epoch—angiosperms dominated, origin of the mammalian
orders including the appearance of the primitive whales.
• Oligocene epoch—origins of the different primate groups including
the apes; tropical rainforests appeared in many continents; pigs,
cats and rhinos appeared; marine life was dominated by mollusks.
Neogene Period
Subdivided into two epochs:
• Miocene epoch—coevolution of angiosperms and insects;
continued speciation of mammals.
• Pliocene epoch—origin of the hominids (Homo)
Did you know that the oldest fossils ever recorded in the Philippines dates
back between 777 to 631 thousand years ago (tya) during the Pleistocene epoch?
These findings were discovered in Kalinga, Cagayan Valley of northern Luzon. It
included remains of rhinoceros, stegodon, brown deer, and early hominins yet
to be identified. The most recent identified hominin is Homo luzonensis or Callao
Man dated 67 tya which was found in Callao Cave, Peñablanca, Cagayan by
Armand Mijares and his team from the University of the Philippines.
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Features of the Phanerozoic Eon
Direction: Copy the table below. Put a check ( ) mark under the column which
best fits the description given in the first column from the left.
Description Cenozoic Mesozoic Paleozoic
1. “Age of Mammals”
2. “Age of Reptiles”
3. “Age of Invertebrates”
4. Marked by time of the Cambrian
explosion and the “mother of mass
extinctions”
5. The longest era, so far, in the
phanerozoic eon.
6. Marked by the dominance and
extinction of dinosaurs
7. Marked by the rise and dominance of
humans and other mammals.
Directions: Fill in the blank with the correct word to complete the statements
below. Write your answers on a separate sheet paper.
1. The _______________________ is a tool that geologists use to subdivide the
history of the Earth into events.
2. The geologic events are subdivided into time intervals which include
______, eras, ______, and ______.
3. The longest time interval (formal) is an _______ and the shortest (in our
notes) is an _______.
4. To construct the geologic time scale, geologists rely on two methods to
determine the age or date of the layers of rocks, these are _____________and
____________ dating.
5. The major part or 88% of the Earth’s history is identified as the
_________________ supereon.
6. The most recent eon is referred to as the ____________________ eon.
7. Geologists subdivided the Precambrian supereon into the _____________
(informal name), ________________, and _______________ eons.
8. The Hadean eon is estimated to have started ____________ billion years ago
(bya), which said to be the age of the Earth.
9. The single-celled organisms, also known as __________________ organisms,
first appeared in the Archean eon which were mostly anaerobic bacteria.
10. By the end of the Proterozoic eon, _________________ organisms arose 1.25
bya, which is evidenced by fossils of the ancient red alga found in Canada.
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11.The _______________________ eon is the more recent eon in the geologic time
scale. This eon is subdivided into: ___________, Mesozoic, and __________
eras.
12. The __________________ era is referred to as the era of “ancient life” which
was mostly dominated by marine ____________________.
13. The __________________ era is referred to as the “middle life” era as
this was in the middle of the phanerozoic eon.
14.The Cenozoic era is subdivided into three periods, they are:
_______________, __________________, and Quaternary.
15.The ____________________ epoch is said to be the time when human
civilizations rose, and human activities changed the face of the Earth.
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Directions: Write the letter of the correct answer on a separate sheet of paper.
1. Which of the following is the SECOND event in the geologic time scale?
A. Eukaryotes arose. C. First multicellular organisms arose.
B. Prokaryotes arose. D. O2 accumulated in the atmosphere.
2. Which of the following represents 88% of the Earth’s history?
A. Cenozoic era C. Phanerozoic eon
B. Mesozoic era D. Precambrian supereon
3. How did the photosynthetic organisms affect the early Earth? They _________
A. depleted the ozone layer.
B. added O2 in the atmosphere.
C. introduced the greenhouse gases into the atmosphere.
D. increased the amount of hydrogen sulfide in the early ocean.
4. Which represents the correct order of appearance, from the earliest to the
most recent group of organisms in the geologic time scale?
A. Ferns, humans, dinosaurs, mammals
B. Fishes, reptiles, seed plants, trilobites
C. Reptiles, fishes, angiosperms, amphibians
D. Ancient red alga, invertebrates, fishes, gymnosperms
5. Which dating method can provide geologists of the age in years of rocks,
fossils, and other ancient materials of the Earth?
A. Relative dating C. Fossil Succession
B. Absolute dating D. All of the given
6. How many mass extinction events were recorded in the geologic time scale?
A. 2 B. 3 C. 4 D. 5
7. When did the "mother of mass extinctions" occur, wiping out more than 90%
of species?
A. Cretaceous period C. Ordovician period
B. Devonian period D. Permian period
8. Which of these is NOT a period of the Paleozoic Era?
A. Carboniferous C. Jurassic
B. Ordovician D. Permian
9. Which of these bests describes the Mesozoic era?
A. Mass extinctions of dinosaurs and large reptiles ended the Mesozoic
era.
B. It was an era marked by the domination of reptiles and flowering
plants.
C. This era is subdivided into the Triassic, Jurassic, and Cretaceous
periods.
D. All of the above.
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10. Which of these bests describes the Archean and the Proterozoic eons?
A. Both eons are subdivisions of the Phanerozoic supereon.
B. No life is possible during these eons because the Earth was still
inhospitable to living organisms.
C. Both eons provided the timeline for simple organisms (both prokaryotes
and eukaryotes) to evolve to give rise to the multicellular organisms
which eventually lead to the diversity of life-forms we have today.
D. All of the above.
11. When did most of the coal beds form which is the main source of the fossil
fuel we have today?
A. Permian period C. Cretaceous period
B. Cambrian period D. Carboniferous period
12. What is the oldest recorded fossil?
A. Fossils of trilobites.
B. Ancient red alga found in Canada.
C. Microfossils of cyanobacteria called stromatolites.
D. Fossils that contain similar chemical signatures as eukaryotic
membranes
13. How old is the oldest recorded fossil that is said to be the evidence of the first
eukaryote?
A. 1.2 byo B. 1.6 byo C. 3.8 byo D. 4.6 byo
14. Which of these bests describes the Cenozoic era? It is/was ___________.
A. dominated by small and huge reptiles called the dinosaurs.
B. dominated by marine invertebrates which included the Cambrian
explosion.
C. the most recent era and has been dominated greatly by the diversified
mammals.
D. largely populated by simple-celled organisms that evolved to become
the first photosynthetic organisms.
15. Modern human beings appeared during which geologic period?
A. Miocene C. Holocene
B. Pliocene D. Pleistocene
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