This Powerpoint Presentation (PPT) is all about Oxygen Revolution and How oxygen exists at the start of the Early Earth. For BS Marine Transportation and BS Marine Engineering

1. O x y g e n
E z r a D a v e I g n a c i o

2. The theory of how oxygen gas (O2) came to the earth and started the
beginning of life.
Oxygenrevolution

3. EarlyEarth
The atmosphere on early
Earth was very different than
what we have today. It is
thought that the first
atmosphere of the Earth was
made up of hydrogen and
helium, much like the gaseous
planets and the Sun.

4. After millions of years of volcanic
eruptions and other internal Earth
processes, the second atmosphere
emerged. This atmosphere was full of
greenhouse gases like carbon dioxide,
sulfur dioxide, and also contained other
types of vapors and gases like water vapor
and, to a lesser extent, ammonia and
methane.
Green House gases

5. >> While there are
many theories of how
life began on Earth, it is
certain that the first
organisms to inhabit
the Earth had to not
need oxygen, as there
was no free oxygen in
the atmosphere.
> This combination of
gases was very
inhospitable to most
forms of life.
Oxygen
-free!
>>> Most scientists agree that the building blocks of life would not have
been able to form if there had been oxygen in the atmosphere at that time.

6. CarbonDioxide
However, plants and other autotrophic
organisms would thrive in an atmosphere
filled with carbon dioxide and one of the
main reactants necessary for
photosynthesis to occur. With carbon
dioxide and water, an autotroph can
produce a carbohydrate for energy and
oxygen as waste. After many plants
evolved on Earth, there was an
abundance of oxygen in the atmosphere.

7. It is hypothesized
that no living thing
on Earth at that
time had a use for
oxygen. In fact, the
abundance oxygen
was toxic to some
autotrophs and
they became
extinct.
Toxic!

8. Beneficial oxygen
Even though oxygen gas couldn't be used directly by living things, oxygen wasn't
all bad for these organisms living during that time.
Oxygen gas floated to the top of the atmosphere where it was exposed to
ultraviolet rays of the sun. Those UV rays split the diatomic oxygen molecules and
helped to create ozone, which is made up of three oxygen atoms covalently
bonded to one another.

9. The ozone layer helped
block some of the UV rays
from reaching Earth. This
made it safer for life to
colonize on land without
being susceptible to those
damaging rays.
Before the ozone layer formed, life had to stay
in the oceans where it was protected from the
harsh heat and radiation.
The
Ozone

10. Since oxygen was so
plentiful in these early
stages of colonization of
land, many of the
ancestors of the species
we know today grew to
enormous sizes. There is
evidence that some types
of insects grew to be the
size of some of the larger
types of birds.
With a protective layer of
ozone to cover them and
plenty of oxygen gas to
breathe, heterotrophs were
able to evolve. The first
consumers to appear were
simple herbivores that
could eat the plants that
survived the oxygen laden
atmosphere.
LandLife!

11. Giveandtake
More heterotrophs could then evolve as
there were more food sources. These
heterotrophs happened to release carbon
dioxide as a waste product of their cellular
respiration.
The give and take of the autotrophs and
heterotrophs were able to keep levels of
oxygen and carbon dioxide in the
atmosphere steady. This give and take
continues today.

12. T h a n k y o u