Life Science-Theories about the beginning of life

1. Lesson 1: The Concept of Life Based on
the Emerging Pieces of Evidences
Prepared by:
Sherie Mae Q. Lozada, RN

2. What was the first
life form?
Life is believed to have existed
on earth for billions of years
now. Scientists do not know
exactly when life began on
Earth. However, they can trace
how life developed and evolved
using some pieces of evidence.
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3. What was the first
life form?
Earth is much older than life.
Based on radioactive decay
studies of rocks, it was revealed
that Earth is around 4.5 billion
years old – 1 billion years older
than the oldest fossils. So how
did life begin? Where did it
come from?
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5. Theories on How Life Begun
1. Extraterrestrial Origin
2. Panspermia
3. Divine Creation
4. Origin from nonliving matter
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6. 1. Extraterrestrial Origin
The hypothesis explains that
life originated on another
planet outside our Solar
System. Life was then carried
to Earth on a meteorite or an
asteroid and colonized Earth.
However, this hypothesis has
not been proven.
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7. 2. Panspermia
The theory presumes
that the “seed” of life
exists all over the
universe and can be
propagated through
space, and that life on
Earth originated from
those seeds.
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8. 3. Divine Creation
Many people believe
that life was put on
Earth by divine
forces. Creation
theories are common
to many of the world’s
religions and cultures.
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9. 4. Origin from nonliving matter
Scientist believed that life arose
on Earth from inanimate matter
after Earth had cooled. They
stated that random events
probably produced stable
molecule that could self-
replicate. Then, natural
selection favored changes in
the rate of reproduction which
eventually led to the first cell.
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10. Primordial Soup Theory
Proponents: Alexander Oparin
and John Haldane
• life started in a primordial soup
of organic molecules
• Some form of energy from
lightning combined with the
chemicals in the atmosphere to
make the building blocks of
protein known as the amino
acids.
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11. Evidence on the first forms of life
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12. Miller-Urey
Experiment
American chemist Stanley Miller
performed an experiment
replicated early Earth conditions.
Together with Harold Urey, he
provided proof that amino acids
and other organic molecules
could be formed.
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13. Miller-Urey Experiment
The atmosphere that Miller
and Urey introduced into the
flasks contained simple
molecules that were probably
present in the early Earth’s
atmosphere: hydrogen, CO2,
methane, water vapor,
nitrogen, ammonia, and
carbon monoxide.
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14. Miller-Urey Experiment
They heated the mixture and
zapped it with electrical sparks
to stimulate lightning. Within
days, a dark, smelly mixture
developed. When this mixture
was analyzed, they found that
many complex molecules had
formed, including some amino
acids, which are the building
blocks of proteins.
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15. Miller-Urey Experiment
Using slightly different
combinations of starting
molecules, Miller and other
scientist where able to
generate many amino acids,
RNA and DNA nucleotides,
lipids, carbohydrates, and
adenosine triphosphate
(ATP).
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16. Fossils
1.Bone Fossils
2.Shell Fossils
3.Plant Fossils
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17. How do fossils form?
Over long periods of time, particles piled up on the remains of organisms and
eventually became sedimentary rocks, preserving the original body patterns
of organism.
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18. Microfossils
• Fossil fragments that can
only be seen by microscope
• Existed in mats and formed
layered structures called
stromatolites.
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19. Stromatolites
a calcareous mound built up of
layers of lime- secreting
prokaryotes, or single-celled
organisms, called cyanobacteria(
the blue-green algae) and trapped
sediment, found in Precambrian
rocks as the earliest known
fossils, and still being formed in
lagoons in Australasia.
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20. Cyanobacteria
• Believed by scientists to be the
first oxygen- producing organisms
that helped evolve the Earth’s
early atmosphere into one that
can support early life forms
• As these microorganisms
continued generating oxygen,
other photosynthetic organisms
evolved and increased the level of
oxygen in the atmosphere.
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21. Cyanobacteria
• This increased the chance of
more and more oxygen
reaction ammonia, a reaction
that results in the release of
nitrogen into atmosphere
• This resulted in the formation
of the ozone layer!
• A rapid evolution of life
occurred after oxygen
became abundant.
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22. ACTIVITY
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