FOSSIL EVIDENCE OF EVOLUTION

The Fossil Record The Fossil Record – made up of all

the fossils ever discovered on Earth provides evidence that species have

changed over time

Fossil – the remains or evidence of once-living organisms

Fossil Formation Mineralization

minerals in water replace the organism’s original material and harden into rock

Carbonization extreme pressure

drives off the organism’s liquids and gases leaving only the carbon outline

Fossil Formation Molds and Casts

Mold – impression of an organism in hardened mud or sand

Cast – a fossil copy of an organism in a rock created by sediment filling in the mold

Fossil Formation Trace Fossils

preserved evidence of the organism’s activity, like footprints

Original Material original tissues

of an organism, like insects in amber (tree sap)

Relative-Age vs. Absolute-Age

Relative-Age – scientists determine the relative order in which rock layers were deposited( Most Accurate when the rock layers are undisturbed.)

Absolute-Age (Radioactive Dating)– scientists use the ratio of unstable isotopes to stable isotopes to find the age of rocks; more precise ex. carbon-14 dating

The Geologic Time Scale a chart that divides Earth’s history

into different time units

Extinctions Extinction – occurs when last

individual organism of a species dies Mass Extinction

when many species become extinct within a few million years or less

there have been 5 mass extinctions in the Phanerozoic eon

Causes of Extinction Sudden change – like meteor impact or

volcanic eruption Gradual change – like tectonic plates or sea

level changes

Biological Evolution the change over time in populations

of related organisms