A phylogenetic tree is a diagram that shows the evolutionary relationships between different organisms, with the common ancestor at the base and more recently evolved organisms at the top. It is based on evidence from fossils, comparative anatomy, DNA, and geology. The tree illustrates the order in which organisms evolved over time and whether they contain certain traits that evolved in ancestral populations.

1. Unit 7:
Phylogenetic
Trees

2. (1) What is a Phylogenetic Tree?
• A diagram used to show the evolutionary
relationships between different organisms.
• Also Includes:
– The common ancestor.
– The order organisms evolved in.
• Based off of Evidence:
– Fossils + Comparative Anatomy
– DNA
– Geology

3. (2) The Common Ancestor
• The organism by which all other organisms
evolved from.
• The most primitive ancestor for that type of
organism.

4. (3) The Parts
• Bottom / Base = Oldest Organism/s
• Top = Most recently evolved organisms
• Organisms after a trait:
– Evolved after that trait existed in populations.
– Contain those traits.
• Organisms before a trait:
– Evolved before that trait existed in populations.
– Do NOT contain those traits.

5. (4) Example
1
2 3 4 5 6
Multicellular
Gills
Lungs
Wings
Live Birth
LimbsFins
Eggs
On 4 On 2