The document discusses several theories for the origin of life on Earth: - Panspermia theory proposes that life originated in space and was transported to Earth via meteors and asteroids. - Primordial soup theory suggests that organic compounds essential for life were created in the early Earth's atmosphere and oceans. - Deep sea vent theory posits that life began in the porous crust of Earth near hydrothermal vents, not on the surface. It then provides a timeline for the major developments of life on Earth from its earliest origins over 4 billion years ago to the emergence of modern humans around 200,000-250,000 years ago. Key events included the first prokaryotes, cyanobacteria that generated oxygen

1. Earth and Life Science
EVOLVING CONCEPT OF LIFE BASED
ON EMERGING PIECES OF EVIDENCE

2. Let me Ask You:
Where do you think life on Earth came from?
Do you know any superstitious belief regarding
the beginning of life on earth?
In your own opinion, where do life on Earth came
from?

3. Theories about the
Origin of Life
Let’s Talk:

4. Theories of the Origin of LIFE
PANSPERMIA
This hypothesis proposes that
microscopic life forms that survived the
effects of space became trapped in debris
that were expelled into space after a
strong collision between planets were
responsible in harbouring life forms.
The panspermia theory argues that life is
originated in space, in spatial ices, and
continuously distributed to the planets by comets
and meteorites.

5. Theories of the Origin of LIFE
Primordial Soup Theory
The idea of the primordial soup was
originally proposed by Alexander Oparin as a
possible explanation for the creation of life on our
planet. The theory states that if energy is added to
the gases that made up Earth's early atmosphere,
the building blocks of life would be created.
According to the theory, organic compounds
essential for life forms were synthesized in the
primitive Earth under prebiotic conditions. The mixture
of inorganic and organic compounds with water on
the primitive Earth became the prebiotic or primordial
soup.

6. Theories of the Origin of LIFE
Deep Sea Vent Theory/
Deep hot Biosphere theory
Postulated by Thomas Gold. This
model suggests that life on Earth did not
begin on surface but instead in the
porosity of its crust.
The discovery of tiny filamental
structures that are similar to bacteria
called nanobes in deep rocks in the
early 90’s supported the claim.

7. Theories of the Origin of LIFE
Creation Theory The concept of divine creation is that all life
forms existing today have been created by a
supreme being.

8. Which of the theories discussed is more likely
convinced you?
Activity:
Why you choose that theory, support your
answer?

9. Historical Timeline
of Life on Earth
Let’s Talk:

10. Ca. 4.6 to 3.8 billion years ago
The early earth is said to be violent and because of the
meteorites and volcanic eruptions. With this condition , zircon
crystal was formed (one of the earliest mineral).
Around this time, debris from the forming solar system
crashed into the early Earth, keeping its surface burning hot.
The Hadean period, named after the Greek
god and ruler of the underworld Hades, is the oldest
eon and dates from 4.5–4.0 billion years ago. This
time represents Earth's earliest history, during
which the planet was characterized by a partially
molten surface, volcanism, and asteroid impacts.
Formation of Earth’s Crust and Ocean

11. Life on Earth initially began with prokaryotes,
discovered in sedimentary rock formations called stromatolites.
These sedimentary rock formations are strong pieces of
evidence that the first microbes might have existed during this time.
During the formation of stromatolites, the sheets of microbes are
captured in the sedimentary particles.
Ca. 3.5 billion years ago
Prokaryotes – is a single-celled organism that lacks a
nucleus and other membrane-bound organelles.
Ex. Bacteria and archaea
Oldest Geological Evidence of Life

12. Ca. 3.0 billion years ago
The first photosynthetic organisms thrived the
earth which is the blue green algae called
cyanobacteria.
Photosynthesis allowed these primitive cyanobacteria
to start converting light energy to chemical energy. As a
result, byproduct oxygen molecules were eventually increased
which transformed the Earth’s atmosphere and paved the way
for the beginning of biodiversity on the planet.
Propagation of Cyanobacteria

13. Ca. 2.0 billion years ago
Geological evidence points out that life was only composed of
prokaryotes until around 2 billion years ago. Modern eukaryotes are
characterized as having-membrane bound organelles like the
mitochondria and nucleus.
Appearance of the first Eukaryotes
Several scientist suspect that this cellular
organelles and molecules may have evolved from
ancient relationships between different bacteria
(endosymbiosis theory).

14. Ca. 1.2 billion years ago
The appearance of the first eukaryotes and the
influx (an arrival) of multicellular organisms occurred 1.2
billion years ago.
During this period, it was believed that
multicellularity occurred several times. According to some
hypotheses, multicellularity was the product of the
symbiotic relationships between cells of similar or different
species that eventually led to interdependency among
organisms
Influx of Multicellular Organisms

15. Ca. 500 milli0n years ago
The Cambrian Explosion
Arthropods, molluscs, fish, amphibians,
synapsids, and diapsids all evolved during the
Paleozoic. Life began in the ocean but eventually
transitioned onto land, and by the late Paleozoic,
great forests of primitive plants covered the
continents, many of which formed the coal beds of
Europe and eastern North America.
Fossil records showed evidence that there was a
drastic increase in the diversity of complex faunal species
during a relatively short time span. The Cambrian
explosion refers to an interval of time in the Cambrian
period when practically all major animal phyla started
appearing in the fossil record.

16. Ca. 251-65.5 milli0n years ago
The Age of Reptiles
The Mesozoic era- the age of
reptiles that has a span of 251-65.5
MYA divided into Triassic, Jurassic and
Cretaceous period.

17. Ca. 200-250 milli0n years ago
Arrival of Modern Human
The Cenozoic era – recent life and based on
paleontological evidence. Homo erectus have
evolved. Paleontological evidence suggests that
modern human might have evolved from Homo
Erectus approximately 250 years ago.
The Cenozoic is Earth's current geological era,
representing the last 66 million years of Earth's history.
It is characterized by the dominance of mammals, birds
and flowering plants, a cooling and drying climate, and
the current configuration of continents

19. Make/create your own
Historical Timeline of Life on
Earth based on the discussion.
Apply your creativity in
designing your timeline.
Activity: