IN: 4/14 • KWL on what you know about the Origin of Life! What is science vs. non-science? K W L
The Origin of Life! Miss Zourkas Biology 1
Earth’s Early History • Key points to learn: • What substances made up Earth’s early atmosphere? • What did Miller & Urey’s experiments show? • What occurred when oxygen was added to the Earth’s atmosphere?
The Formation of Earth • Earth was not born from a single event…Cosmic debris were attracted to one another over time (~100 mil years). • While the planet was young, it was struck by objects possibly as large as Mars. These collisions made enough heat to melt the entire globe. • Once Earth melted, the elements rearranged according to density, forming Earth’s core. Radioactive decay made enough heat to convert the core to molten rock.. • The less dense elements moved towards the top to form the surface, the solid crust. The least dense elements (hydrogen & nitrogen) formed the atmosphere.
The Formation of Earth • Earth’s early atmosphere probably contained: hydrogen cyanide, carbon dioxide, carbon monoxide, nitrogen, hydrogen sulfide, and water. • A few breaths of this would kill you! • It has been inferred that ~4 billion years ago the world cooled enough to allow rocks to form on Earth. Volcanoes ruled the Earth for millions of years. • ~3.8 billion years ago the Earth cooled enough for water to stay a liquid…and thunderstorms ruled forming the current day oceans.
The First Organic Molecules • In the 1950’s, Miller & Urey designed an experiment that attempted to recreate Earth’s early environment. • Step 1: Filled a flask with Hydrogen, Methane, Ammonia, and H2O • Step 2: Passed electric sparks through mixture to represent lightning. • Results: After a few days -> Amino Acids began to accumulate
Spectacular Results! • Miller & Urey’s experiment showed us that the compounds/elements of life existed in Early Earth. • What do we know now? • The experiment was not completely accurate • With more knowledge, experiments have produced organic compounds • 1995, Miller produced cytosine and uracil…what are these?
Well…How do we breathe Oxygen now? • Microscopic Fossils (microfossils) of prokaryotic bacteria have been found in rocks 3.5 billion years old and these lived without oxygen! • Photosynthetic bacteria were producing oxygen that mixed with ocean water forming rust • Rust fell to the floor and is mined today as iron ore. • Oxygen formed our atmosphere and turned sky/ocean from brown to blue. • Anaerobic (organisms that don’t need oxygen) organisms struggled but aerobic (organisms that need oxygen) organisms did well, were “fit”. • The rise of oxygen in the atmosphere drove some life forms to extinction, while others evolved new, more efficient way to use oxygen for breathing.
Endosymbiotic Theory: Simple to Complex • Endosymbiotic Theory: eukaryotic cells arose from living communities formed by prokaryotic organisms. The prokaryotes devolved & formed eukaryotic cells. • Once these Eukaryotic cells formed, they reproduced Sexually, which allowed for variation of species…which started Evolution!