The Origin and Early Evolution of Life Chapter 18

Learning Objectives 1.Differentiate between chemical evolution and organic evolution. 2.Describe the conditions on the primitive earth predicted by laboratory experiments that favored the spontaneous development of organic molecules. 3.Explain the probable sequence in the origin of the first cells, and describe how this cell interacted with its environment. 4.Review the theories proposed to explain the origin of eukaryotic organelles.

The Big Bang billion years ago all matter in the universe was compressed into a mass the size of our sun Sudden instantaneous explosion of matter and energy throughout the known universe

Earth Forms About 4.6 to 4.5 billion years ago Minerals and ice orbiting the sun started clumping together Heavy minerals moved to Earth’s interior, lighter minerals floated to surface –Produced outer crust and inner mantle Chemical evolution produced the primordial sea and the early atmosphere that would support the biosphere of the future. p. 288

Earth Is “Just Right” for Life The Planet: If smaller in diameter, gravity would not be great enough to hold onto atmosphere If closer to sun, water would have evaporated If farther from sun, water (the solvent of life) would have been locked up as ice Early Atmosphere: Hydrogen gas Nitrogen Carbon monoxide Carbon dioxide No gaseous oxygen p. 288

Stanley Miller’s Experiment Mixed methane, hydrogen, ammonia, and water Simulated lightning Amino acids and other small molecules formed What, at a minimum, is needed to form a cell-like structure from these molecules? p. 289

Possible Sequence START: “Chemical Evolution” “Organic Evolution” informational molecules separation of environments END p. 291 Why is RNA believed to be the first genetic information? Why is DNA a better molecule for heredity?

The First Cells Prokaryotic heterotrophs Describe what this means. Secured energy through anaerobic metabolism …Describe. –No oxygen present …Why not? p. 291 Is there fossil evidence for these first cells?

Fossil Evidence photosynthetic eubacteria Oxygen producing permits aerobic respiration 3.5 bya 2.1 bya1.2 bya p. 292

Possible Origin of ER & Nuclear Envelope p. 294 aka: Autogenous Theory

Endosymbiotic Theory Cyanophora paradoxa p. 295