Name:___________________
Period___________________
Evidence of Geologic Time Scale
Directions: With your group analyze the 5 pieces of evidence. Rate each
evidence for quality on a scale of 0 – 3. Than record textual evidence of
that reflects the cause of changes throughout earths history on your
chart.
Evidence 1
Early Earth Was Purple!
Later, Chlorophyll turned it green
Was our world always Green? Evidence suggests that the earth was once purple. Our
world is made green because plants contain chlorophyll. Chlorophyll absorbs blue and
red light waves from the sun and reflects back the green that colors plants. There was a
time that earth didn’t have plants. Before plants earth was purple. Scientist have found
evidence that early bacteria absorbed green light waves and reflected back purple. These
primitive bacteria used retinal instead of chlorophyll to harness energy. "Primitive
microbes that used retinal to harness the sun's energy might have dominated early Earth. Being
latecomers, microbes that used chlorophyll could not compete directly with those utilizing retinal,
but they survived by evolving the ability to absorb the very wavelengths retinal did not use," said
Shil DasSarma, a microbial geneticist at the University of Maryland.
So how did our world become green?
As multi celled plants emerged the need for a new way to absorb the suns energy was
needed. Chlorophyll emerged as the new and more efficient way to absorb the suns
energy. Because chlorophyll was more efficient green plants took over the planet. When
earth was still young the atmosphere-lacked oxygen making it easier for retinal to form.
This may also be a new indicator of life on other planets. If you happen to see a planet that
is at the early stage of evolution, and you're looking for green life, you might miss it.
Apr 11, 2007 09:52 GMT · By Stefan Anitei
Contributing scientist:
William Sparks, an astronomer at the Space Telescope Science Institute (STScI) in Maryland.
Shil DasSarma, a microbial geneticist at the University of Maryland.
David Des Marais, a geochemist at NASA's Ames Research Center in California
Evidence 2
Earth’s original atmosphere was rich in methane, ammonia, water vapour,
and the noble gas neon, but it lacked free oxygen. It is likely that hundreds
of millions of years separated the first biological production of oxygen by
unicellular organisms and its eventual accumulation in the atmosphere.
Evidence 3 – the history of Earth’s atmosphere
Earth is believed to have formed about 5 billion years ago. In the first 500
million years the atmosphere that emerged consisted of hydrogen (H2),
water vapor, methane (CH4) , and carbon oxides. Prior to 3.5 billion years
ago the atmosphere consisted of carbon dioxide (CO2), carbon monoxide
(CO), water (H2O), nitrogen (N2), and hydrogen. Ancient earth’s
environment did not have oxygen. Evidence of this was found in early rock
formations. One billion years ago, early aquatic organisms called bluegreen algae began using energy from the Sun create energy through the
process of photosynthesis. Photosynthesis created and released oxygen
into the atmosphere. This oxygen accumulated in the atmosphere,
triggering a massive ecological disaster with respect to early existing
organisms. As oxygen in the atmosphere increased, CO2 decreased and a
protective oxygen layer called the ozone layer formed. The thin layer of
ozone that surrounds Earth acts as a shield, protecting the planet from
irradiation by UV light.
The amount of ozone required to shield Earth from lethal radiation, is
believed to have been in existence 600 million years ago. At this time, the
oxygen level was approximately 10% of its present atmospheric
concentration. Prior to this period, life only existed in the ocean. The
presence of ozone enabled organisms to develop and live on the land.
Ozone played a significant role in the evolution of life on Earth, and
allowed life as we presently know it to exist.
Evidence 4 - How Has The Atmosphere Changed
video
https://www.youtube.com/watch?v=sturoUChNo4
Evidence 5 - History of the Earth in 5 1/2 minutes
https://www.youtube.com/watch?v=8qnnoePeHlk
Evidence 6 - Meteor and Asteroid Strikes as Causes of
Climate Change
Most meteors and asteroids burn up in the earth's atmosphere incinerating
all or most of the incoming material before reaching the Earth's surface.
When a very large body collides with the Earth it can cause huge
destruction and change global climate.
The comet/meteorite impact in Siberia theory of climate change has been
considered to account for the extinction of the dinosaurs 65 million years
ago. And another impact site dated at 65 millions years can be found on
the tip of the Yucatan Peninsula in the Gulf of Mexico, Central America.
Evidence, such as a thin layer of clay deposited at this time all over the
globe contains the rare element iridium found only in meteors. An impact
from an object 10km across could release huge quantities of vaporized
material into the atmosphere, blocking out the Sun; Cause a shock wave
for hundreds of miles, Produce firestorms for thousands of miles, Rain
debris containing the iridium coating plants, or Create globally distributed
acid rains.
Read more at http://www.ehso.com/climatechange/climatechangecausesmeteorites.php#roseov2eoo95GGP8.99
Additional prezi
https://prezi.com/i9cqhihadz-d/precambrian-mass-extinction/
Name: ___________________ Partner’s name: ________________________
Period: __________ Number ___________
Evidence Quality
Rating (0-3)
1. Purple Earth
2. Earth’s Original
Atmosphere
3. The History of
Earth’s
Atmosphere
4. How has the
Atmosphere
changed?
5. History of the earth
in 5 ½ minutes
6. Meteor and
Asteroid
Strikes
Evidence of change
Directions Continued…
3. After reading each piece of evidence and filling in the chart, create a model
that explains what caused changes throughout geologic time. Work in pairs or
individually.
Geologic time Model
4. Discuss models as a class and come up with the best model to support all
evidence.