Chapter 24 Questions - Questions for Chapter 24 1. Describe...

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Questions for Chapter 24 1. Describe three recent developments in the study of life on Earth that make life elsewhere seem more plausible. - We have learned that life arose quite early in Earth’s history, suggesting that life might also form quickly on other worlds with the right conditions. - Laboratory experiments have shown that the chemical constituents thought to have been common on Earth combine readily into complex organic molecules. This suggests that life might have arisen through naturally occurring chemistry; the same chemistry could have given rise to life on many other worlds. - The discovery of microscopic living organisms that can survive in conditions similar to those on at least some other worlds in our solar system, suggests that the necessities of life may be common in the universe. 2. How do we study the history of life on Earth? Describe the geological time scale and a few of the major events along it. - We learn about the history of life on Earth through the study of fossils, relics of organisms that lived and died long ago. Most fossils fall to the bottom of a sea and are gradually buried by layers of sediment. Erosion and tectonic activity later expose the fossils. Radiometric dating confirms relative ages and gives us fairly precise absolute ages for fossils. - The geological time scale is the time scale used by scientist to describe major eras in Earth’s past. About 4.5 billion years ago, the Earth was formed and there was heavy bombardment or possible sterilizing impacts. 3.5 billion years ago, oldest microfossil evidence of life. 2.8 billion years ago, buildup of oxygen. About 540 million years ago, there was a Cambrian explosion of animal diversity. 200 million years ago, dinosaurs were prominent then mammals became prominent. 3. How far back in Earth's history did life exist? Where is a likely place for the formation of life? - A few very old rocks suggest life was already thriving on Earth 3.5 billion years ago and possibly for several hundred million years before that. Strong evidence comes from rocks called stromatolites, which look similar to large bacterial mats found in some locations today. Life began after the end of heavy bombardment. Fossil evidence points to life already thriving 3.5 billion years ago. 4. What is the theory of evolution, and why is it so critical to our understanding of the history of life on Earth? Describe the logic that led Darwin to propose the theory. - The theory of evolution is the unifying theory through which scientists understand the history of life on Earth. Scientist had recognized evidence of evolution in the fossil record but Darwin explained how species might undergo change. The fossil record provides strong evidence that evolution has occurred, while Darwin’s theory of evolution explains how it occurs. -
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This note was uploaded on 02/12/2012 for the course ASTR 1110 taught by Professor Jpc during the Spring '08 term at University of Georgia Athens.

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Chapter 24 Questions - Questions for Chapter 24 1. Describe...

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