Craniata & Vertebrara Flashcards
What are the 5 characteristics of Chordates?
Pharyngeal slits, notochord, hollow nerve cord, post-anal tail, endostyle
What were the pharyngeal slits originally used for?
Filter/suspension feeding of early chordates
What is the notochord? What is it made out of and what benefit did it provide evolutionarily? What has it evolved into in modern vertebrates?
A structure running dorsally along the truck and tail of all chordates. It is made of fibrous material with a fluid filled center that supported movement. It has evolved into the bones of the vertebral column, but is still present in embryonic form.
What is the post-anal tail and what benefits does it have?
It is an extension of muscle and the notochord that runs past the anus. Allows greater movements.
What is the endostyle? What was its original purpose?
The endostyle binds iodine to make hormones and is a precursor to the thyroid gland. It was originally used for filter feeding and digestion.
What are characteristics that are found in, but not exclusive to, Chordates?
Segmented body columns, coelom (true body cavity), bilateral symmetry, cephalization
What are plesiomorphic traits?
Primitive or ancestral characteristics
What are apomorphic traits?
Unique, or derived, characteristics
“This animal has a head.”
What type of trait is this? Why?
It is a plesiomorphic trait because it is not unique or specific to any particular group.
“This animal has feathers.”
What type of trait is this and why?
It is an apomorphic trait because it is a derived character that is unique to that specific group.
What are synamorphic traits?
Shared derived characteristics
In cladistics, what type of traits are used to establish clades?
Apomorphic and synamorphic traits are used to create monophyletic lineages/clades
________ lineages, which include all organisms in a lineage plus their common ancestor(s). Give an example.
Monophyletic. Ex) avians must be included with all other reptiles
What are the “protochordates?” Why are they called that?
Hemichordates, urochordates, and cephalochordates. They share all or some of the chordate characteristics and are often referred to as “pre-Chordates.”
