The Fossil Record

1
The Fossil Record

• Section 3
• This section explains how fossils form and how
  they can be interpreted. It also describes the
  geologic time scale that is used to represent
  evolutionary time.

2
Fossils and Ancient Life

• Scientists who study fossils are called___.

paleontologists
3
Fossils and Ancient Life

• What is a fossil record?
• It is information about past life that is based
  on fossils.

4
Fossils and Ancient Life

• What evidence does the fossil record provide?
• It provides evidence about the history of life on
  Earth and how different groups of organisms,
  including species, have changed over time.

5
Fossils and Ancient Life

• Species that died out are said to be ___.
• extinct

6
Fossils and Ancient Life

• Is the following sentence true or false?
• About half of all species that have ever lived on
  Earth have become extinct.
• FALSE

7
How Fossils Form

• Circle the letter of each sentence that is true
  about fossils.
• Fossils can include footprints, eggs, or other
  traces of organisms.
• The quality of fossil preservation varies.

8
How Fossils Form

• How do fossils form in sedimentary rock?
• Sediments settle to the bottom of lakes and seas
  and bury dead organisms. The weight of upper
  layers of sediment compresses lower layers into
  rock and turns the dead organisms into fossils.

9
Interpreting Fossil Evidence

• List the two techniques paleontologists use to
  determine the age of fossils.
• Relative dating
• Radioactive dating

10
Interpreting Fossil Evidence

• Circle the letter of each sentence that is true
  about relative dating.
• It determines the age of a fossil by comparing
  its placement with that of fossils in other
  layers of rock.
• It uses index fossils.
• It provides no information about absolute age.

11
The History of Life

• Is the following sentence true or false?
• Older rock layers are usually closer to Earths
  surface than more recent rock layers.
• false

12
The History of Life

• Is the following sentence true or false?
• Scientists use radioactive decay to assign
  absolute ages to rocks.
• true

13
The History of Life

• The length of time required for half of the
  radioactive atoms in a sample to decay is called
  a(an) _____.
• half-life

14
The History of Life

• The use of half-lives to determine the age of
  a sample is called_____.
• radioactive dating

15
The History of Life

• How do scientists calculate the age of a
  sample using radioactive dating?
• They measure the amount of remaining radioactive
  isotopes it contains. The smaller the amount, the
  older the sample.

16
The History of Life

• Is the following sentence true or false? All
  radioactive elements have the same half-life.
• false

17
Geologic Time Scale

• Fill in the missing eras and periods in the
  geologic time scale below.

Era Cenozoic Cenozoic Mesozoic Mesozoic Mesozoic Paleozoic Paleozoic Paleozoic Paleozoic Paleozoic Paleozoic
Period Quaternary Tertiary Cretaceous Jurassic Triassic Permian Carboniferous Devonian Silurian Ordovician  
Time (millions of years ago) 1.8 present 65 1.8 145 65 208 145 245 208 290 245 363 290 410 363 440 410 505 440  
18
Geologic Time Scale

• Circle the letter of the choice that lists the
  eras of the geologic time scale in order from the
  most recent to oldest
• Cenozoic, Mesozoic, Paleozoic

19
Geologic Time Scale

• Circle the letter of each sentence that is true
  about the geologic time scale.
• The scale is used to represent evolutionary time.
  
• Major changes in fossil organisms separate
  segments of geologic time.