1. Unit 1 Lesson 3 Evidence of Evolution
Essential Question: What evidence supports the theory of evolution?
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2. Fossil Hunt How do fossils form? p30
Unit 1 Lesson 3 Evidence of Evolution
Fossil Hunt
How do fossils form?
Evidence that organisms have changed over time can be found in amber, ice, or sedimentary rock.
Sedimentary rock is formed when particles of sand or soil are deposited in horizontal layers. This often occurs as mud or silt hardens.
The most basic principle of dating rocks and the remains of organisms inside is “the deeper it is, the older it is.” (Law of Superposition)
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3. Fossil Formation Sequence Map

4. p31
Unit 1 Lesson 3 Evidence of Evolution
Fossils are the remains or imprints of once-living organisms.
Many fossils form in sedimentary rock.
Fossils form when a dead organism is covered by a layer of sediment or mud.
Over time, more sediment settles on top of the organism.
Minerals in the sediment replace the body’s material with minerals that harden over time.
The organism completely decomposes, leaving behind an imprint (Cast Fossil)
Most often, the dead organism is recycled back into the biological world by scavengers, decomposers, or the process of weathering.
How do fossils form?

5. How do fossils show change over time?
p31
Unit 1 Lesson 3 Evidence of Evolution
How do fossils show change over time?
All of the fossils that have been discovered make up the fossil record.
By examining the fossil record, scientists can learn about the history of life on Earth.
There are gaps in the fossil record in which a fossil has not been discovered.
Fossils found in newer layers of Earth’s crust tend to have physical or molecular similarities to present-day organisms.
Fossils from older layers are less similar to present-day organisms.
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6. How do fossils show change over time?
p31
Unit 1 Lesson 3 Evidence of Evolution
How do fossils show change over time?
Fossils that help fill in gaps in the fossil record are called transitional fossils.
7) Identify
Organism lives on the edge of a body of water, and possible on both land and water.
8) Infer
The organism has a tail and fins like a fish, but lives above water like a four-legged vertebrate
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7. More clues … What other evidence supports evolution? p32
Unit 1 Lesson 3 Evidence of Evolution
More clues …
What other evidence supports evolution?
Many fields of study provide evidence that modern species and extinct species share an ancestor.
A common ancestor is the most recent species from which two different species have evolved.
Structural data, DNA, developmental patterns, and fossils all support the theory that populations change over time.
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8. Developmental Similarities P32-33
Common Structures
Related organisms share structural traits
Structures may be reduced in size or have different function.
Similar DNA
Scientists compare amino acids that make up cytochrome c proteins
The greater number of similarities the more recently the two species shared a common ancestor
Developmental Similarities
Embryology
Scientists compare development of different species and look for similar patterns and structures.
P32-33
The leg of a frog and the wing of a bird serve very different purposes, but the bones in their limbs are similar in structure. What does this suggest about frogs and birds?

9. How do we know organisms are related?
P34-35
Unit 1 Lesson 3 Evidence of Evolution
How do we know organisms are related?
Fossils give evidence for how certain species changed gradually over time.
Fossil and DNA evidence support the hypothesis that modern whales evolved from hoofed mammals that lived on land.
Scientists have examined transitional characters of extinct species to see how changes happened.
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10. How do we know organisms are related?
P34-35
Unit 1 Lesson 3 Evidence of Evolution
How do we know organisms are related?
Fossil evidence and skeletons of fossils suggest how a land mammal might have gradually changed to an aquatic whale.
40 mya – Dorudon
Unused Structures
Unused Structures
Molecular evidence also shows that the DNA of whales and hoofed mammals is very similar.
Present day - Whale

11. p.35 How do we know organisms are related? Hippopotamus
Unit 1 Lesson 3 Evidence of Evolution
How do we know organisms are related?
Species
DNA Sequence
Hippopotamus
(hoofed animal)
TCC TGGCA GTCCA GTGGT
Humpback Whale
CCC TGGCA GTGCA GTGCT
Circle the pairs of nitrogen bases (G,T,C,or A) that differ
A = Adenine
T – Thymine
C – Cytosine
G - Guanine
Lets go to the lab…….