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Lecture Biology: Chapter 25 - Niel Campbell, Jane Reece

Chapter 25 - The history of life on earth. This chapter define radiometric dating, serial endosymbiosis, Pangaea, snowball Earth, exaptation, heterochrony, and paedomorphosis; describe the contributions made by Oparin, Haldane, Miller, and Urey toward understanding the origin of organic molecules; explain why RNA, not DNA, was likely the first genetic material;. | Chapter 25 The History of Life on Earth Overview: Lost Worlds Past organisms were very different from those now alive. The fossil record shows macroevolutionary changes over large time scales including The emergence of terrestrial vertebrates The origin of photosynthesis Long-term impacts of mass extinctions. MacroEvolution: Large Scale Changes Over Time Figure 25.1 What does fossil evidence say about where these dinosaurs lived? Concept 25.1: 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: 1. Abiotic synthesis of small organic molecules. 2. Joining of these small molecules into macromolecules. 3. Packaging of molecules into “protobionts.” 4. 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 likely contained water vapor and chemicals released by volcanic eruptions (nitrogen, nitrogen oxides, carbon dioxide, methane, ammonia, hydrogen, hydrogen sulfide). A. I. Oparin and J. B. S. Haldane hypothesized that the early atmosphere was a reducing environment. Stanley Miller and Harold Urey conducted lab experiments that showed that the abiotic synthesis of organic molecules in a reducing atmosphere is possible. However, the evidence is not yet convincing that the early atmosphere was in fact reducing. Instead of forming in the atmosphere, the first organic compounds may have been synthesized near submerged volcanoes and deep-sea vents. Amino acids have also been found in meteorites. Deep Sea Vents Figure 25.2 A window to early life? Abiotic Synthesis of Macromolecules Monomers --> Polymers Small organic molecules polymerize when they are concentrated on hot sand, clay, or rock. Replication and metabolism are key properties of life. Protobionts are aggregates of abiotically produced molecules surrounded by a . | Chapter 25 The History of Life on Earth Overview: Lost Worlds Past organisms were very different from those now alive. The fossil record shows macroevolutionary changes over large time scales including The emergence of terrestrial vertebrates The origin of photosynthesis Long-term impacts of mass extinctions. MacroEvolution: Large Scale Changes Over Time Figure 25.1 What does fossil evidence say about where these dinosaurs lived? Concept 25.1: 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: 1. Abiotic synthesis of small organic molecules. 2. Joining of these small molecules into macromolecules. 3. Packaging of molecules into “protobionts.” 4. 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 likely contained water vapor and