What characteristics are responsible for the branching off of the arthropods from earlier animals?
eucoelomates with a hard segmented body
What characteristics do all arthropods have in common?
hard exoskeleton called a cuticle
What level of organization do these organisms demonstrate?
organ system level
How many tissue layers do these organisms have?
triploblastic
What are the 5 recognized subphyla in this phylum?
Trilobita
Checlicerata
Crustacea
Myriapoda
Hexapoda
When do they show up in the evolutionary history?
Precambrian
Where are they found?
worlwide
Type of Excretory System
excretory glands
Type of Circulatory System
Open system with dorsal contractile heart
Type of Respiratory system
body surfaces
Type of Nervous System
dorsal ganglia