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The following will be discussed in this chapter: Changing life on a changing earth, conditions on early Earth made the origin of life possible, the fossil record chronicles life on Earth, as prokaryotes evolved, they exploited and changed young Earth, eukaryotic cells arose from symbioses and genetic exchanges between prokaryotes,. | Chapter 26 The Tree of Life An Introduction to Biological Diversity Overview: Changing Life on a Changing Earth Life is a continuum Extending from the earliest organisms to the great variety of species that exist today Geological events that alter environments Change the course of biological evolution Conversely, life changes the planet that it inhabits Figure 26.1 Geologic history and biological history have been episodic Marked by what were in essence revolutions that opened many new ways of life Concept 26.1: Conditions on early Earth made the origin of life possible Most biologists now think that it is at least a credible hypothesis That chemical and physical processes on early Earth produced very simple cells through a sequence of stages According to one hypothetical scenario There were four main stages in this process 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 many chemicals released by volcanic eruptions As material circulated through the apparatus, Miller and Urey periodically collected samples for analysis. They identified a variety of organic molecules, including amino acids such as alanine and glutamic acid that are common in the proteins of organisms. They also found many other amino acids and complex, oily hydrocarbons. RESULTS Figure 26.2 Miller and Urey set up a closed system in their laboratory to simulate conditions thought to have existed on early Earth. A warmed flask of water simulated the primeval sea. The strongly reducing “atmosphere” in the system consisted of H2, methane (CH4), ammonia (NH3), and water vapor. Sparks were discharged in the synthetic atmosphere to mimic lightning. A condenser cooled the atmosphere, raining water and any dissolved compounds into the miniature sea. EXPERIMENT Electrode Condenser Cooled water containing organic molecules H2O Sample for chemical analysis Cold water . | Chapter 26 The Tree of Life An Introduction to Biological Diversity Overview: Changing Life on a Changing Earth Life is a continuum Extending from the earliest organisms to the great variety of species that exist today Geological events that alter environments Change the course of biological evolution Conversely, life changes the planet that it inhabits Figure 26.1 Geologic history and biological history have been episodic Marked by what were in essence revolutions that opened many new ways of life Concept 26.1: Conditions on early Earth made the origin of life possible Most biologists now think that it is at least a credible hypothesis That chemical and physical processes on early Earth produced very simple cells through a sequence of stages According to one hypothetical scenario There were four main stages in this process 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 .
