Comparative Vertebrate Anatomy
Hypothesizing Evolutionary Relationships
I. Vertebrate Classification (Review)
Kingdom Animalia
• Common Characteristics: Multicellular;
eukaryotic; heterotrophs that ingest their food; lack
cell walls; reproduce sexually
Phylum Chordata
• Common Characteristics: Notochord,
Pharyngeal Gill Slits, Dorsal Nerve Cord
Subphylum Vertebrata
• Common Characteristics: Backbone
(vertebral column), Endoskeleton, Brain
and Skull
Classes:
• Chrondrichthyes,
Osteichthyes, Amphibia,
Reptilia, Aves, Mammalia
II. Evolutionary Relationships
A. Organisms are classified using 2 main assumptions:
1. The more similar the genes and physical traits of two species are,
the more closely related they are.
2. The similarities were inherited from a common ancestor.
B. Predicting Evolutionary Relationships
1. Evolutionary relationships can be predicted using diagrams. Each
diagram is a hypothesis of how groups of organisms are related to
one another.
a. Phylogenetic Trees - Hypothesize evolutionary relationships
among organisms and predicts when important traits evolved.
b. Cladograms - Hypothesize evolutionary relationships among
organisms based on significant physical traits.
Phylogenetic Tree
Figure 36-2, MillerLevine, Biology
Cladograms
Family tree that branches systematically at points (nodes) representing specific
trait possessed by some groups, but not others.
Evolution of Individuals in the Workplace (Matt Groening, 1985)
III. How To Make a Cladogram
More Complex
Branch:
Name or Type of Organism
Derived Traits
Organisms branching to right
HAVE this trait.
Node:
Organisms
branching to left
DO NOT have this
trait.
Specific trait or traits
Primitive Traits
Less Complex
Example
AIRPLANE
CAR
BIKE
SLEIGH
wheels
modes of transportation
travels at 17,500 mph
wings
engine
SPACE
SHUTTLE
Vertebrate Cladogram
Dinosaurs?
BIRDS
Dinosaurs?
REPTILES
AMPHIBIANS
Mammary
Glands; Hair
4-Chambered Heart; Endothermy;
Up and Down Movement
FISH
Amnion; Internal Fertilization
4 Limbs; Lungs; Double-Loop Circulatory
System; Highly Complex Digestive System
Brain Case and Backbone;
Endoskeleton; Dorsal Nerve Cord
(primitive traits)
MAMMALS