2. • How do scientists know what organisms
looked like if they don’t exist anymore?
1. How do fossils form?
• Fossils – remains or traces of
prehistoric life
• Fossil record – complete
record of all fossils discovered
• Helps us understand how life
forms have changed over time.
3. Carbonization Amber
Petrified wood
Mineralization (petrified):
“turned into stone”
Altered remains: direct evidence
Amber:
hardened resin (sap) of
ancient trees; preserves
delicate insects
Carbonization:
effective in preserving leaves &
delicate animal forms (carbon
film left behind)
Molds:
impression of an organism in a
rock
Cast:
fossil copy of an organism in a
rock
Mold & Cast
4. Which refers to the impression of an organism
found in a rock?
A. Cast
B. Fossil
C. Mold
D. Trace fossil
Cast
Fossil
M
old
Trace
fossil
0 000
45
5. Which refers to a fossil that is turned into stone?
A. Carbonization
B. Mineralization
C. Mold
D. Trace fossil
Carbonization
M
ineralization
M
old
Trace
fossil
0 000
45
6. Animal footprints
Copralite (dung &
stomach contents)
Animal burrows (worm
burrow)
Gastrolith (polished
stomach contents)
Altered remains: indirect evidence
Trace fossils:
preserved evidence of the activity of
an organism
7. • Original Materials: original
tissues are preserved
– Most common with teeth,
bones, and shells
– Extremely rare to find
remains of an entire animal
– Example: Fully preserved,
frozen mammoth found in
Siberia (Lyuba)
1. How do fossils form?Baby woolly mammoth:
4 ft. long
between 10,000 &
40,000 yrs old
8. Which is the preserved evidence of the activity of
an organism?
A. Cast
B. Fossil
C. Mold
D. Trace fossil
Cast
Fossil
M
old
Trace
fossil
0 000
45
9. • Instead of dating fossils directly,
scientists date the rocks the fossils are
embedded inside.
• Revisiting the rock cycle:
2. How is geologic evidence used to
help determine the age of fossils?
10. Which kind of rocks are most fossils found in?
A. Igneous rocks
B. Sedimentary rocks
C. Metamorphic rocks
Igneousrocks
Sedim
entaryrocks
M
etam
orphicrocks
0 00
45
11. • The geologic time scale is
a chart that divides Earth’s
4.6 billion year history into
different time units.
1. Eons
2. Eras
3. Periods
4. Epochs
2. How is geologic evidence used to help determine the
age of fossils?
longest
shortest
12. Which era and period are we currently in?
A. Mesozoic and
Neogene
B. Precambrian and
Hadean
C. Cenozoic and
Paleogene
D. Cenozoic and
Quaternary M
esozoicand
Neogene
Precam
brian
and
Hadean
Cenozoicand
Paleogene
Cenozoicand
Quaternary
0 000
45
13. • Scientists now understand that sudden
disappearance in fossils in rock layers are
evidence of extinction events.
• Extinction occurs when the last individual
organism of a species dies.
• A mass extinction occurs when many species
become extinct within a few million years or less.
• Extinctions occur when environments change
(either gradually or suddenly).
3. What causes species to change over
time?
15. The fossil record contains evidence that
five mass extinction events have occurred
during the Phanerozoic eon.
3. What causes species to change over
time?
16. How many major extinction events have
occurred in Earth’s history?
A. 2
B. 3
C. 4
D. 5
2
3
4
5
0 000
45
17. • As fossils were discovered, patterns emerged
that showed many different species with
similar body structures.
• Evidence suggests that species change over
time.
• Change over time = Evolution (to evolve)
• Biological evolution is the change over time
in populations of related organisms.
3. What causes species to change over
time?
18. • The fossil record
is evidence
that horses
descended from
organisms for
which only fossils
exist today.
• There are many
other examples of
this that we will
learn about.
