Early Earth Notes

The earth was formed 4.6 billion years ago! So what was it like?

Early Earth Landscape:

History of the Earth In a single day. Courtesy: NASA / Goddard Space Flight Center

12.00 to 4.00am “The Big Bang” No life A planet with poisonous gases in the air, no soil and a hot sea.

4.00am to 8.00pm Single celled organisms, called stromatolites, begin to produce oxygen.

Just before 8.30pm First marine plants

8.50pm Jellyfish and simple marine organisms

Just after 9.00pm Trilobites and creatures of the Burgess Shale

10.00pm Plant life of the carboniferous and the first land creatures.

11.00pm to 11.45pm Reign of the Reptiles – Dinosaurs Rule!

1 minute and 17 seconds to midnight First humans appear.

Clock analogy for some key events in evolutionary history

What was early Earth like? Very hot! The friction of colliding meteorites could have heated its surface The compression of minerals and the decay of radioactive materials heated its interior

Atmosphere? Volcanoes might have spewed lava and gases, relieving some pressure in Earth’s interior These gases helped form Earth’s ancient atmosphere  Little free oxygen  A lot of water vapor and other gases  Carbon dioxide, nitrogen, hydrogen, methane, ammonia

How did life originate? Spontaneous Generation  Idea that nonliving material can produce life  Can you give me an example of what Aristotle was seeing?

Spontaneous Generation Francesco Redi was the first to disprove this idea.  How do you think he did it?

Spontaneous Generation Louis Pasteur went on to disprove it as well.

Meteorites What might have been carried on the meteorite?

Soups On! Earth’s atmosphere was probably made up of gases that contained organic elements. What are they??

Primordial Soup Energy fueled chemical reactions among these gases which combined them into organic compounds.

Primordial Soup These molecules were washed into the oceans, mixing together

Theories on how life began Alexander Oparin  Life began in the oceans  Energy from the sun, lightning, and Earth’s heat triggered chemical reactions to produce small organic molecules

Chemical Evolution Harold Urey and Stanley Miller provided evidence to support this.

Chemical Evolution

Miller Urey Results After a week, they found several kinds of amino acids, sugars, and other small organic molecules Evidence supported Oparin’s hypothesis! Life began in the oceans and Energy from the sun, lightning, and Earth’s heat triggered chemical reactions to produce small organic molecules

1. The earth was formed ~4.5 billion years ago 2. It took ~500 million years for the crust to solidify bya Earth might have cooled enough for water in its atmosphere to condense; led to millions of years of rainstorms with lightning – ENOUGH TO FILL EARTH’S OCEANS! 4. The oldest fossils of microorganisms (earliest evidence of life) 3.5 billion years old, embedded in rocks in western Australia Prokaryotes dominated from 3.5 to 2 billion years ago. - During this time, the first divergence occurred: Bacteria and Archaebacteria

Oxygen began accumulating in the atmosphere about 2.7 billion years ago. a. Cyanobacteria are photosynthetic prokaryotes that are still present today  produced oxygen.

Banded iron formations are evidence of the age of oxygenic photosynthesis – approximately 2 BYA in photo

5. The oldest eukaryotic fossils are ~2 billion years old. a. Symbiotic community of prokaryotes living within larger prokaryotes.  Mitochondria and chloroplasts 6. The oldest fossils of multicellular organisms are ~1.2 billion years old.

7. Fossilized animal embryos from Chinese sediments 570 million years ago.

8. Plants, fungi, and animals began colonizing land ~500 million years ago. a. First plants transformed the landscape… b. Then animals were able to take advantage of new niches  Mammals evolved 50 to 60 million years ago.

Some major episodes in the history of life.