1. Evidences of Evolution

2. How old is the Earth?
Geological records reveal that Earth is about 4.5 billion years old.
Fossils of single cell bacteria have been found from 3.5 billion years ago.

3. I-Fossils
Fossils can be found in a variety of substances and can be made from a variety of objects such as:
Ice
Amber (solidified tree sap)
Tar
Shells
Bone

4. Fossils cont’d.
Fossils are found in layers of sedimentary rock such as shale
The fossils found in lower layers of rock are older than those in layers closest to the top
Newest
Oldest

5. II- Comparative Anatomy
Parts such as bones and organs are examined and compared between organisms
The more similar the structure, the more likely the two share a common ancestor
Homologous structures = those with similar structure, but may have different function
Example: the bones of the wing of a bat are similar in type and layout to those of our arm, but they are used differently

6. Homologous Structures

7. Analogous Structures
These structures have similar function, but when examined do NOT have similar structure
These do NOT provide evidence for common ancestry
Why do whales and sharks both have fins?
One is a fish and one is a mammal
However they live in the same environment

8. Vestigial Structures
These are structures that no longer have a function in a species
Since they are not harmful to survival they are not selected against and continue to be passed on
What structures do we have that could be considered vestigial?

9. III-Comparative Embryology
While adults of different species do not resemble each other, the embryos shed light on unexpected common ancestry
Early on it is difficult to distinguish the embryos of humans from that of chickens and salamanders!
The more stages of development in common, the more closely related the two species are
Examine the diagram on the next slide, who is our closest relative?

11. IV- Comparative Cytology
Cyto- sounds like cytoplasm, which is found in cells
-ology = study of
Cytology therefore is the study of cells
The more similar the cell parts between two species, the more closely related they are
For example two cells that have chloroplasts and cell walls are more closely related than one with chloroplasts and one without

12. V- Comparative Biochemistry
Biochemistry is the field of science that focuses on chemicals and their reactions in living things
If two organisms have similar chemical compounds (such as a particular enzyme) they are closely related
DNA is a chemical compound, therefore the more similar the sequence of bases between two species, the more closely related they are

13. What do these forms of evidence tell us?
The more of these items two organisms have in common, the more closely related they are
If organisms share structures and substances they are said to have a….
COMMON ANCESTOR!