1. Part 2 Evidence of Common ancestry
Unit 3
Part 2 Evidence of Common ancestry
Interpreting Fossil Evidence to show evolution of organisms

2. 1. Interpreting Fossil Evidence to show evolution of organisms
Copyright Pearson Prentice Hall

3. Fossils Fossil records tell the Earth’s story.
Over years many many layers of rock have formed.
Many fossils are found within layers of rock. Fossils are the preserved remains or traces of organisms that lived in the past

4. Relative Dating
In relative dating, the age of a fossil is determined by comparing its placement to that of fossils in other layers of rock.

5. LAW of SUPERPOSITION
Rock layers form in order by age—the oldest on the bottom, with more recent layers on top

6. Index Fossil
In Relative dating you are comparing 1 fossil to another, generating a history. For this you need an INDEX FOSSIL
An index fossil is a species that is recognizable and that existed for a short period but had a wide geographic range.

7. Absolute Dating . Absolute Dating= radioactive dating
Paleontologists determine the age of fossils using the fact that elements decay into measureable radioactive quantities. Scientists use radioactive decay to assign an absolute age to rocks
Using radioactive decay, C12-C14scientists can determine true age of a fossil.

8. Cladogram A branching diagram representing a
Hypothesis about the evolution of groups of
organisms from a common ancestor

9. 2. Homology of Anatomy is evidence to show evolution of Organsims

10. Homologous Structures
Similar structures in different species but perform different functions
because they share a common ancestor
Ex: human arm, dog front limb, horse leg, whale fin
These “LOOK the SAME”
But have different functions An

11. Analogous Structures Analogous structures
Distantly related species have different structures that have the same function.
Ex: wing of butterfly & bird
These “look different”
But have “same function”

12. Vestigial Structures Vestigial structures
Structures reduced in size & often unused
Remains of functional structures inherited from an ancestor
Ex: leg & hip bones in pythons & whales

13. 3. How Molecular Evidence shows Evolution of Organisms

14. DNA and Protein Homology
Also called biochemical evidence
Compares biomolecules such as DNA, RNA or amino acid sequences between organisms
Related organisms have
more of the same
molecules in common

15. 4. Developmental Homology shows evidence of evolution

16. Embryonic Development
Common development of the organism throughout it’s
embryonic development before being born.