Post on 15-Jul-2015
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Ch. 6.1 – Fossil Evidence of Evolution
Lesson 1-1
• 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.
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
Which refers to the impression of an organism
found in a rock?
A. Cast
B. Fossil
C. Mold
D. Trace fossil
Cast
Foss
il
Mold
Trace
foss
il
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Which refers to a fossil that is turned into stone?
A. Carbonization
B. Mineralization
C. Mold
D. Trace fossil
Carboniza
tion
Min
eraliz
ation
Mold
Trace
foss
il
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45
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
Unaltered remains
• 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
Which is the preserved evidence of the activity of
an organism?
A. Cast
B. Fossil
C. Mold
D. Trace fossil
Cast
Foss
il
Mold
Trace
foss
il
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Lesson 1-3
• 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?
Which kind of rocks are most fossils found in?
A. Igneous rocks
B. Sedimentary rocks
C. Metamorphic rocks
Igneous r
ocks
Sedimenta
ry ro
cks
Meta
morp
hic ro
cks
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Lesson 1-4
• 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
Which era and period are we currently in?
A. Mesozoic and Neogene
B. Precambrian and Hadean
C. Cenozoic and Paleogene
D. Cenozoic and Quaternary
Meso
zoic
and Neogene
Preca
mbria
n and H
adean
Cenozoic
and Pale
ogene
Cenozoic
and Quate
rnary
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Lesson 1-5
• 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?
Evidence of the
meteorite impact
(65 mya)
Lesson 1-5
The fossil record contains evidence that five mass extinction events have occurred during the Phanerozoic eon.
3. What causes species to change over time?
How many major extinction events have occurred in Earth’s history?
A. 2
B. 3
C. 4
D. 5
2 3 4 5
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Lesson 1-5
• 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?
Lesson 1-5
• 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.