Fossils Record Evolution 13

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Blinn College *

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MISC

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Anthropology

Date

Oct 30, 2023

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docx

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Fossils Record Evolution 13.2 Fossils : Any evidence of an organism from more than 10,000 years ago. - Ammonite fossils are common in land-locked Oklahoma, indicating that what is now the central United States was once covered by an ocean. - Fossils allow researchers to test predictions about evolution. For example: Tikaalik provided direct fossil evidence of the connection. Fossil Fuels: Coal, oil, and natural gas are the decomposed remains of plants and other organisms preserved by compression. Impression Fossils : Form when an organism presses against soft sediment, which then hardens, leaving an outline or imprint of the body. Decomposition and tissue damage were minimal in the absence of oxygen: scavengers could not reach the dead. Usually, the fossil record is incomplete, meaning that some of the features marking the transition from one group to another are not recorded in fossils. Phanerozonic eon: most fossils came from here. Phanero (visible), and “life,” (-zonic). Relative dating: Places a fossil into a sequence of events without assigning it a specific age. - With lower rock strata presumed to be older than higher layers - The farther down a fossil is, the longer ago the organism lived. Absolute Dating: To assign an age to a fossil by testing either the fossil itself or the sediments above and below the fossil. - Radiometric Dating: a type of absolute dating that uses radioactive isotopes as a “clock.” - Each isotope of an element has a different number of neutrons. - Some isotopes are naturally unstable, which causes them to emit radiation as they radioactively decay. - Each radioactive isotope decays at a characteristic and unchangeable rate, its half-life. Half-life: the time it takes for half of the atoms in a sample of a radioactive substance to decay.

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