BIO 200 Chapter Notes - Chapter 1: Geologic Time Scale, Radiometric Dating, Absolute Dating
30 Aug 2016
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Today"s common species, such as a dragon fly, were much different three hundred million years ago: they are so different that they would be unrecognizable to today"s average human, example: Present dragon fly: wingspan of a human hand. Past dragon fly: wing span of 70 centimeters (over 2 feet) These groups of insects used to be much different than they are today: larger, different diets, different habitats. Scientists believe these insects would not be able to survive on earth today. The oxygen concentration of the earth has changed and prevents any of these insects or the other huge amphibians to survive: the earth is constantly changing. How can a scientist tell how old a fossil is: the layering tips off the age of the fossil, the development of sophisticated techniques were created in the 20th century: Studying decay rates of isotopes: scientists can infer environmental conditions to date the fossil.
