​Evidence of evolution

Layers of sedimentary rock contain fossils
• new layers cover older ones, creating a record over time
• fossils within layers show that a succession of organisms have populated Earth throughout a long period of time

the tiktaalik was a significant discovery because it was the missing link that connected land animals to sea animals (land animals evolved from sea animals)

Actual ages of rocks can be determined using radioisotopes—isotopes that decay in a predictable pattern.
Half-life is the time during which one half of the atoms in a radioisotope sample decay, changing into another element.
To date an event, the original concentration of the isotope must be known or estimated, and the
half-life of the isotope must be known. The amount of isotope remaining is indicative of
how much time has passed since the event.

Paleomagnetic dating relates ages of rocks to patterns in Earth’s magnetism.
Earth’s magnetic poles move and occasionally reverse.
Sedimentary and igneous rocks preserve a record of Earth’s magnetic field at the time
they were formed.

What are Homologous structures?
Similar structure
Similar development
Different functions
Evidence of close evolutionary relationship
• recent common ancestor