The Fossil Record

Chapter 17.1

0The fossil record provides evidence about the history of life on Earth. It also shows how different groups of organisms, including species, have changed over time.

How Fossils Form0The formation of any fossil depends on

a precise combination of conditions.0Most fossils form in sedimentary rock.

(test question)0sedimentary rock0The weight of layers of sediment

gradually compresses the lower layers and, along with chemical activity, turns them into rock.0fossil formation

Radioactive Dating 0A half-life is the length of time required

for half of the radioactive atoms in a sample to decay. (test question)

index fossil0Scientists also use index fossils

to compare the relative ages of fossils. To be used as an index fossil, a species must be easily recognized and must have existed for a short period but have had a wide geographic range. (test question)

The first organisms on earth were most like today’s bacteria. (test question)

Assignment

0Take five notes from the video

Earth Science: Fossils