EARTH 7 Lecture Notes - Lecture 6: Tyrannosaurus, Tyrannosauroidea, Binomial Nomenclature
10/17/17
● Cladograms
○ You can swivel branches
○ You can prune branches
○ We only apply scientific names at NODES
● A taxon is a group of organisms
○ Ex. Animalia » Dinosauria » Vertebrata » Tyrannosauroidea
● Species
○ Binomial nomenclature
■Tyrannosaurus rex
● Genus
● Specific epithet
● Genus
○ Tyrannosaurus
■ Can have multiple species in one genus
● How do we figure out relationships?
○ Need to determine shared derived characters
■ Aka evolutionary novelties
1. Animals with backbones
2. Animals with 4 bony limbs
3. Animals with feathers
● Examples of characters
○ Physical features
■ Wings, hair color, backbone
○ Behavioral features
■ Maternal care
○ Biochemical features
■ DNA or Protein sequence
● Homologous vs. Convergent Characters
○ Homologous character: similar due to inheritance from common ancestor
○ Convergent character: similar but NOT inherited from a common ancestor
■ Independently acquires
● Convergent Characters
○ Usually these characters are only superficially similar
○ Similarity is often due to similar FUNCTION
● Homologous characters
○ Arms, legs, fins, and wings in these groups are all pretty different, but their
underlying similarity is indicative of their shared ancestry
● Groups are “Defined” by the evolutionary novelties that set them apart from other
species
● Feather are DERIVED for birds, but ANCESTRAL for an eagle. Backbones are
DERIVED for vertebrates, but ANCESTRAL for birds
Document Summary
We only apply scientific names at nodes. A taxon is a group of organisms. Can have multiple species in one genus. Aka evolutionary novelties: animals with backbones, animals with 4 bony limbs, animals with feathers. Homologous character : similar due to inheritance from common ancestor. Convergent character : similar but not inherited from a common ancestor. Usually these characters are only superficially similar. Similarity is often due to similar function. Arms, legs, fins, and wings in these groups are all pretty different, but their underlying similarity is indicative of their shared ancestry. Groups are defined by the evolutionary novelties that set them apart from other species. Feather are derived for birds, but ancestral for an eagle. Four limbs is an evolutionary novelty that defines tetrapods. As long as the ancestors of snakes had limbs (they did), snakes are tetrapods. Include ancestor + all descendants = good. Origin and diversification in the water, and the evolution of jaws.
