Describe general features of the history of life on Earth, including generally accepted dates and sequences of the geologic time scale and characteristics of major groups of organisms present during these periods (STEM-BIO11/12-IIIC-G-8). Specific Objectives: 1. Identify the date, eon, era, period, epoch and describe the major events base on Geologic Time Scale. 2. Differentiate the types of fossils. 3. Appreciate the history of life on earth by making a personal timeline.

1. G E N B I O 2 , Q 1 , W E E K 2

3. WHAT IS GEOLOGIC TIME SCALE
Calendar of events of earth’s history of
life where they are arranged in
chronological order.

5. WHAT IS GEOLOGIC TIME SCALE
EON
ERA
PERIODS
EPOCHS

7. FOUR ERAS IN GEOLOGICAL TIME SCALE
1. Precambrian
2. Paleozoic Era
3. Mesozoic Era
4. Cenozoic Era

8. PRECAMBRIAN
which is 542 million years ago where single-celled
organisms came into existence.
The end of this span is the rise of few more
complex animals in the oceans such as Jellyfish.
There was still no life on land, and the atmosphere
was just beginning to accumulate the oxygen
requirement for higher-order animals to survive.

9. PALEOZOIC ERA
an era that began with the Cambrian Explosion a relatively rapid
period of speciation kicked off a long period of life flourishing on
Earth.
There are a huge number and kinds of living organisms from the
ocean that moved towards the land.
It is believed that plants were the first to migrate towards land,
followed by invertebrates and many other species also appeared
and thrived on land.
The end of this Era comes with the largest mass extinction in the
history of life on Earth, wiping out 75percent of marine life and
nearly 70 percent of life on land.

10. MESOZOIC ERA
“age of dinosaurs”
The climate during this Era was very humid
and tropical, which many lush, green plants
sprouted all over the Earth.
Herbivores thrive and small mammals came
into existence, birds developed evolved from
the dinosaurs.

11. CENOZOIC ERA
which began 65 billion years ago to the present
this final era on the GTS wherein smaller mammals
survived and become dominant.
The climate of this Era is cooler and drier compared to
the Mesozoic Era.
This is an “Ice Age” which covered most temperate
regions of the Earth with glaciers.
All species of life- including humans evolved into their
present-day form throughout this era.

12. WHAT IS FOSSILS?
evidence of organisms that lived in the
past.
They may be actual remains like burrows,
nests, and dinosaurs’ footprints or even the
ripples created in our prehistoric shore.

13. SIX WAYS OF FOSSILIZATION
1. Unaltered preservation- wherein small organisms or past trapped in
amber, hardened plant sap is being observed.
2. Per mineralization/ Petrification- the organic contents of bone and wood
are replaced by silica, calcite, or pyrite, forming a rock-like fossil.
3. Replacement- hard parts are dissolved and replaced by other minerals,
like calcite, silica, pyrite, or iron.
4. Carbonization/ or Coalification- the other elements are ionized and only
the carbon remained.
5. Recrystallization- the hard parts are converted into more stable minerals
or small crystals turned into larger crystals.
6. Authigenic preservation – molds and casts are formed after most of the
organisms have been destroyed or dissolved.

15. HOW DO WE MEASURE THE AGE OF
FOSSILS?
1.Relative Dating
2.Absolute Dating

16. RELATIVE DATING
This means that the fossil is compared
to something for which an age is already
known.
Index fossils- use several types of fossils
to aid in relative dating.
Fossils that are identified to be found
only within a very specific age span.
Examining the layers of rock or strata
can also be useful.

17. ABSOLUTE DATING
It is determined by the actual age of the
fossil and through radiometric dating
using radioactive isotopes.