Evolution The Fossil Record

The Fossil Record A fossil is a trace of a long-dead organism. Many different kinds of fossils have been found. Molds - imprints Casts – rocklike models Amber Tracks of animals

Types of Fossils

The Fossil Record (cont’d) The history of the Earth and its life-forms can be inferred by examining the fossil record.

The Fossil Record (cont’d) The fossil record shows Forms of organisms appeared, lasted for long periods of time and then disappeared (became extinct). Followed by newer forms of life that also eventually disappeared.

The Fossil Record (cont’d) There were several mass extinctions. Probably resulted from drastic changes in the environment.

Distribution of fossils Law of superposition New geologic strata (layers of rock) are deposited on top of older strata. Relative age: one fossil or rock is older than another.

Distribution of fossils Absolute age: actual age in years. Can be determined by radiometric means (half-life).

Distribution of fossils (cont’d) Using these data, scientists have determined that the Earth is about 4.5 billion years old.

Biogeography The study of geographical distribution of fossils and of living things. Shows that new organisms arise in areas where similar now-extinct forms once lived.