Fossils

What is a fossil?

• A fossil is the preserved remains of a once-living organism.

A fossil may be:

• an original skeleton or shell;

• a mold or cast;• material that has

replaced the once living thing;

• traces such as footprints or worm tubes

What are the fossil types?

• Body fossils – actual parts of an organism, unaltered or altered

bones, shells, leaf imprints

• Trace fossils – evidence of life that is not a body fossil

tracks, burrows, casts

Body fossils

Trace Fossils

More on trace fossils

• Tracks – impressions of passage of living things

Fossil

records

document

the course

of life through

time

Fossil Evidence of Evolution

9

• Fossils document evolutionary transition• The oldest known bird fossil is the Archaeopteryx

• It is intermediate between bird and dinosaur

• Possesses some ancestral traits and some traits of present day birds

• Archaeopteryx was first found in 1859

Fossil Evidence of Evolution

10

Fossil of Archaeopteryx

Fossil Evidence of Evolution

11

Recent discoveries–Four-legged aquatic mammal

• Important link in the evolution of whales and dolphins from land-dwelling, hoofed ancestors

–Fossil snake with legs–Tiktaalik: a species that bridged the gap

between fish and the first amphibian

Fossil Evidence of Evolution

12Whale “missing links”

Fossil Evidence of Evolution

13

Homology of the bones of the forelimb of mammals

Anatomical Evidence for Evolution