How Life Began Wake County Biology Curriculum

http://www.youtube.com/watch?v=H2_6cqa2cP4

Early Earth The Earth formed about 4.6 billion years ago. It formed by debris coming together due to gravity.

Early Earth The melted Earth formed layers with the most dense material at the center and the lighter materials forming the crust. The lightest materials formed the atmosphere.

Early Earth As the Earth cooled, water condensed and formed oceans.

Early Earth Storms dominated the atmosphere because the Earth was still hot. Therefore there was much lightning.

Early Earth The atmosphere was a mixture of hydrogen cyanide, methane, carbon dioxide and monoxide, nitrogen, hydrogen sulfide, ammonia, water, and other chemicals.

Early Earth There was NO oxygen on Earth. The oceans were brown due to large amounts of dissolved iron.

Early Earth The Moon was closer so it appeared larger than today. Debris was still bombarding the Earth from the new solar system.

Under these conditions, could life evolve? Early Earth Under these conditions, could life evolve?

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How did life begin?

"Primordial soup" is a term introduced by the Soviet biologist Alexander Oparin. In 1924, he proposed a theory of the origin of life on Earth through the transformation or “evolution” of carbon molecules created by Earth’s ancient environment.

JUST KIDDING!

First Organic Molecules Stanley Miller and Harold Urey In the 1950’s, these two scientists wanted to find out if organic molecules could form under the conditions of the new planet Earth. Urey and Miller filled a container with hydrogen, methane, ammonia, and water to represent the atmosphere. They heated it to represent volcanic activity.

First Organic Molecules www.uic.edu

First Organic Molecules They sealed it to keep out other living things such as bacteria. They sent sparks through it to simulate the lightning.

First Organic Molecules www.uic.edu

First Organic Molecules They waited to see what would happen. They thought they would have to wait months. However, after just a few days, they checked it and found 13 out of 20 amino acids, and nucleic acids.

First Organic Molecules www.uic.edu

Biochemistry is the study of the structure and function of cellular components such as proteins, carbohydrates, lipids, nucleic acids and other biomolecules. These are the chemicals of life we studied earlier in the year.

Microspheres Under certain hot conditions, amino acids form proteinoid microspheres. Similar to cell membranes, they are selectively permeable.

Cell Membranes Simple fatty acids clumped together then formed naturally occurring phospholipids.

Simple carbohydrates give the newly forming cells energy.

Finally, the most accepted theory states that RNA was the first nucleic acid that allowed the first protocells to replicate.

After time, the RNA evolved into simple DNA.

The First Prokaryotes The latest and most accepted hypothesis of where the first prokaryotes evolved is at deep ocean thermal vents.

ocean-ridge.ldeo.columbia.edu

The First Prokaryotes These volcanic vents would have the heat energy, the chemicals, and the water needed for simple life forms to evolve.

Quick Geologic Activity You and a partner will have 5 events/organisms On post-it notes, guess when they first appeared on earth