Fossils

Objective: Explain fossil and trace fossil, distinguish their meanings, and apply them to a described case.

Fossil: A fossil is preserved evidence of past life, including remains or activity traces. Trace fossil: A trace fossil records an organism's activity rather than its body. Fossils provide evidence of organisms and environments, but preservation is selective. Hard tissues, rapid burial, and suitable sediments often increase preservation chances. An organism's absence from one sample does not establish its global extinction. Correlation is strongest when fossil ranges and geological relationships agree. Environmental reconstruction should combine biological clues with rock characteristics because transport can move remains away from their original living environment. Application: A rock preserves the outline of an ancient shell. This most directly illustrates fossil. Preserved footprints document movement across ancient sediment. This most directly illustrates trace fossil.

Objective: Explain index fossil and preservation bias, distinguish their meanings, and apply them to a described case.

Index fossil: A useful index fossil has broad geographical occurrence and a relatively limited time range. Preservation bias: Organisms and environments differ in their likelihood of leaving recoverable fossils. Fossils provide evidence of organisms and environments, but preservation is selective. Hard tissues, rapid burial, and suitable sediments often increase preservation chances. An organism's absence from one sample does not establish its global extinction. Correlation is strongest when fossil ranges and geological relationships agree. Environmental reconstruction should combine biological clues with rock characteristics because transport can move remains away from their original living environment. Application: The same short-lived widespread fossil correlates separated strata. This most directly illustrates index fossil. Hard shells are preserved more often than many soft tissues. This most directly illustrates preservation bias.

Objective: Explain paleoenvironment and extinction, distinguish their meanings, and apply them to a described case.

Paleoenvironment: A paleoenvironment is a past environment inferred from multiple geological and biological clues. Extinction: Extinction occurs when a lineage has no surviving members, though the fossil record may be incomplete. Fossils provide evidence of organisms and environments, but preservation is selective. Hard tissues, rapid burial, and suitable sediments often increase preservation chances. An organism's absence from one sample does not establish its global extinction. Correlation is strongest when fossil ranges and geological relationships agree. Environmental reconstruction should combine biological clues with rock characteristics because transport can move remains away from their original living environment. Application: Marine fossils and sediment textures support a former shallow sea. This most directly illustrates paleoenvironment. A formerly present species disappears from later evidence. This most directly illustrates extinction.