Chapter 1.4 The Origin of Life

What was the Earth like 3.6 billion years ago?

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

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

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

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

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.