1. Systematics and the Phylogenetic Revolution
Cladograms

2. Cladistics Derived Ancestral Cladistics
Similarity that is inherited from the most recent common ancestor of an entire group
Ancestral
Similarity that arose prior to the common ancestor of the group
Cladistics
Compare derived and ancestral similarities
Only shared derived characters are considered informative in determining evolutionary relationships

3. Identification of Derived vs. Ancestral Characters
Comparison of any pheno- or genotype
Recognizable character states
“teeth” amniote vertebrates (birds, reptiles, mammals)
Presence in most mammals and reptiles
Absent in birds and turtles

4. “Teeth” Nearest outgroups of amniotes (amniotic eggs)
Amphibians and Fish
Teeth are present (in many others as well)
Presence of teeth in mammals and reptiles (came after amniotes) considered ancestral
Absent in birds and turtles = derived

5. Example of Derived vs. Ancestral Mammal common ancestry
Hair
Shared derived character in mammals
Only seen in the most recent common ancestor
Lungs
Ancestral character
Also present in amphibians and reptiles
Evolved prior to the common ancestor or mammals
Lungs don’t show a closer relationship between mammals than reptiles or amphibians
Doesn’t set mammals apart
Hair suggests that all mammal species share a common ancestor that existed more recently than the common ancestor of mammals, amphibians and reptiles
Sets mammals apart from other species

6. Constructing a Cladogram – Step 1
Depicts hypothesis of evolutionary relationships
Polarize the data
Determine whether or not the characters are derived or ancestral
Comparison to an outgroup
Species or group of species that is closely related to, but not a member of, the group of study
Lamprey, Shark, Salamander, Lizard, Tiger, Gorilla, Human
Lamprey = outgroup

7. Constructing a Cladogram – Step 2
Construction
Clade
Species that share a common ancestor (evolutionary units)
Shown by derived characteristics
Group of clades that share derived characteristics
Amniotes  amniotic membrane
Mammals  hair

8. What about convergent evolution?
Characteristic has evolved independently
No common ancestor
Shows a false relationship
Homoplasy
Shared character state that has not been inherited from a common ancestor
Frogs  no tail
Should be related to Gorillas, humans  no tail ???????
However, Frogs  no amniotic membrane and hair  gorillas, humans have amniotic membrane and hair
Frogs are closer to salamanders because one less change occurred (just loss of tail)

9. Phylogenetics and Comparative Biology
Homologous  common ancestor  divergent evolution
Analogous  homoplastic structures  no common ancestor  convergent evolution
Parental care  homologous
Dinosaurs, Crocodiles and birds
Saber teeth  homoplastic
Many cat like animals, carnivores