Chapter 26 - An Introduction to Biological Diversity

Chapter 26 - An Introduction to Biological Diversity -...

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Chapter 26 Class Notes – An Introduction to Biological Diversity – Page 1 Max Sauberman AP Biology – Mr. Schilp Chapter 26 The Tree of Life: An Introduction to Biological Diversity Changing Life on a Changing Earth: Life is a continuum extending from the earliest organisms to the variety of species that exist today. Geological events change the course of evolution. Conversely, life changes the planet that it inhabits. Geologic history and biological history have been episodic, marked by revolutions that opened many new ways of life. Conditions on early Earth made the origin of life possible: Chemical and physical processes on early Earth may have produced very simple cells through a sequence of stages: Abiotic synthesis of small organic molecules Joining of these small molecules into polymers Packaging of molecules into protobionts Origin of self-replicating molecules Synthesis of Organic Compounds on Early Earth: Earth formed about 4.6 billion years ago, along with the rest of the solar system. Earth’s early atmosphere contained water vapor and chemicals released by volcanic eruptions. Experiments simulating an early Earth atmosphere produced organic molecules from inorganic precursors, but such an atmosphere on early Earth is unlikely. Instead of forming in the atmosphere, the first organic compounds may have been synthesized near submerged volcanoes and deep-sea vents. Extraterrestrial Sources of Organic Compounds: Some organic compounds from which the first life on Earth arose may have come from space. Carbon compounds have been found in some meteorites that landed on Earth. Looking Outside Earth for Clues about the Origin of Life: The possibility that life is not restricted to Earth is becoming more accessible to scientific testing.
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Chapter 26 Class Notes – An Introduction to Biological Diversity – Page 2 Abiotic Synthesis of Polymers: Small organic molecules polymerize when they are concentrated on hot sand, clay, or rock. Protobionts: Protobionts are aggregates of abiotically produced molecules surrounded by a membrane or similar structure. Experiments demonstrate that protobionts could have formed spontaneously from abiotically produced organic compounds, like membrane-bounded droplets called liposomes, formed when lipids are added to water. The RNA World and the Dawn of Natural Selection:
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This note was uploaded on 03/17/2011 for the course BIO 101 taught by Professor Sullivan during the Spring '08 term at Harvard.

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Chapter 26 - An Introduction to Biological Diversity -...

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