Evidence of Evolution
Part II
The study of living organisms
reveals secrets of ancestry
Theory of Evolution
 All life on Earth descended from a common
ancestor
 Life originated as a simple form, and
became more diverse and complex over
time
Evidence in Organisms
 “Evolution proceeds by modifications of
organisms which already exist”
Evidence in Organisms
I.
Homologous Structures
* Definition
* Examples (Can you give detailed descriptions of
homologous bones?)
I. Homologous Structures

Homologous Structures

Evidence in Organisms
II. Similarities in Embryonic
Development
•
All animals:
 cleavage, morula, blastula,
layering after blastula (gastrula)
•
All Vertebrates: What did you observe?
Similarities in Embryonic
Development
The limbs of all tetrapods develop from limb
buds in similar ways (see below).
Similarities in Embryonic
Development
How evidence of Evolution?
Evidence in Organisms
III. Vestigial Structures
• definition:
• Examples:
•
•
•
•
Eyes on blind cavefish
Human coccyx (tailbone)
Femurs on pythons, whales
Wings on a Kiwi bird
• How evidence of evolution?
Evidence in Organisms
 What evidence suggests that life forms
today share a common ancestor?
 Animal life:
– Bone homology
– Embryological comparisons
 All life:
– Biochemical evidence
 DNA/Proteins
 Energy reactions
Question
 Why do scientists believe that all life on
Earth descended from a SINGLE common
ancestor?
 Why don’t we think that several “trees of life”
exist? (One for vertebrates, one for
invertebrates, one for plants, one for fungi,
etc?)
ANSWER
D
–N
A
II. Evidence in Organisms
 Evidence that Life forms change over time
 Vestigial Structures
– Definition
– Examples
 Artificial Selection
 Peppered Moth