1. Chapter 1.4
The Origin of Life

2. What was the Earth like 3.6 billion years ago?

3. Black, brown and gray….no greenery
Rugged landscape. Jagged rocks. Little soil.
No visible living things

4. Difference in Atmosphere
The atmosphere was different from today’s atmosphere
Early Earth: Nitrogen, water vapor, carbon dioxide and methane most abundant
Present day: Nitrogen and oxygen most abundant. The other gases found in small amounts.
You would not have been able to breathe in early Earth’s atmosphere

5. Hypotheses about early life on earth
Did not need oxygen
Unicellular
Lived in the ocean
Resemble bacteria that live today in places without oxygen such as polar ice caps, hot springs
These bacteria can survive extreme conditions

6. How did early life form first come to be?
Scientist reason that the first life forms on earth probably arose from nonliving materials
Harold Urey and Stanly Miller
American Scientists
1953: designed an experiment in which they created conditions of early Earth in their laboratory
They placed water and a mixture of gases into a flask. They were careful to keep oxygen and unicellular organisms out
Then they sent an electric current through the mixture to simulate lightning.
Within a week, the fluid darkened and small chemical units were found. If these units were joined together, they could form proteins-one of the building blocks of life

7. The first cells
In experiments similar to Miller and Urey’s, other scientist succeeded in producing chemical units that make up carbohydrates and nucleic acids
Scientists hypothesize that small chemical units of life formed gradually over millions of years in Earth’s waters
Eventually some of the large chemicals accumulated and became the first cells
Fossil records support these hypotheses.
Fossils are traces of ancient organisms that have been preserved in rock or other substances.