Phylogenies and Fossils Lecture
Textbook Reference: Chapter 23 in Biology How Life Works (2nd ed.)
Sections 23.1 – 23.2; pp.464 to 474
Required Reading: Required Reading: Sections 23.3 and 23.4 (pages
474 to 483)
Systematics
What is systematics?
The study of biological diversity and its origins
What is the main difference between phylogenetics and taxonomy?
- Phylogenetics: study of evolutionary and genetic relationships among
organisms
- Taxonomy: classification and naming of organisms
Phylogeny
• The process of speciation can be depicted in a phylogenetic tree
Process of speciation can be depicted in a phylogenetic tree
On a phylogenetic tree:
• What do the branches represent?
Diverging populations
• What do nodes represent?
Last common ancestors
• What are descendent species?
Have risen from ancestral forms
Phylogenetic Trees are Hypotheses
• What does the branching order represent?
Hypothesizes the evolutionary relationship within a group
Page | 1
, • The tree below proposes:
1. closest living relatives of birds are crocodiles and alligators
2. closest relatives of all tetrapod vertebras are lungfish
Sister Groups
• What are sister groups?
2 groups that are each other’s closest relatives
How are sister groups determined?
Looking to see how recently two groups share a common ancestor (node)
Explain why the three trees below are the same
Nodes can be rotated without changing evolutionary relationships
**Order DOESN’T matter, relationship DOES matter
Page | 2
Textbook Reference: Chapter 23 in Biology How Life Works (2nd ed.)
Sections 23.1 – 23.2; pp.464 to 474
Required Reading: Required Reading: Sections 23.3 and 23.4 (pages
474 to 483)
Systematics
What is systematics?
The study of biological diversity and its origins
What is the main difference between phylogenetics and taxonomy?
- Phylogenetics: study of evolutionary and genetic relationships among
organisms
- Taxonomy: classification and naming of organisms
Phylogeny
• The process of speciation can be depicted in a phylogenetic tree
Process of speciation can be depicted in a phylogenetic tree
On a phylogenetic tree:
• What do the branches represent?
Diverging populations
• What do nodes represent?
Last common ancestors
• What are descendent species?
Have risen from ancestral forms
Phylogenetic Trees are Hypotheses
• What does the branching order represent?
Hypothesizes the evolutionary relationship within a group
Page | 1
, • The tree below proposes:
1. closest living relatives of birds are crocodiles and alligators
2. closest relatives of all tetrapod vertebras are lungfish
Sister Groups
• What are sister groups?
2 groups that are each other’s closest relatives
How are sister groups determined?
Looking to see how recently two groups share a common ancestor (node)
Explain why the three trees below are the same
Nodes can be rotated without changing evolutionary relationships
**Order DOESN’T matter, relationship DOES matter
Page | 2
