L12: Phyla Hemichordata and Chordata Flashcards
Describe the general body structure of hemichordates What anatomical feature is shared by echinoderms and hemichordates? How does the nervous system of hemichordates differ from the nervous system of annelids and arthropods? Name five anatomical features that are unique to chordates Why is the evolution of jaws and paired fins considered to be a major evolutionary development? Describe counter-current exchange and understand why it is important
What animals are in the phylum Hemichordata?
Acron worms and pterobranchs (small animals that live in deep water)
T/F Hemichordates are protosomes
False: Deuterostomes
Hemichordates are divided into three body parts:
Proboscis, collar, trunk
Regarding Hemichordates..
T/F Open circulatory system
True
What are gill slits? What are their function?
Act as like a throat
Connect digestive tract to ourside
Aids in gas exchange
What differentiates chordate and hemichordate nervous systems from other animals?
Dorsal nerve cord
Rather than ventral in other animals
Describe a tripartite coelom
Three body cavities that are separated
What are the three subphylums in phylum chordata?
Cephalochordata (head chordates)
Urochordata (tail chordates)
Craniata (animals with skulls)
What are the 5 features all Chordata have?
Notochord
Dorsal, hollow nerve tube
Pharyngeal slits
Postanal tail
Endostyle
What is the notochord? What is its function?
Contains cells with large vacules containing water and fluid. Creates an internal pressure that pushes against membrane
Supportive structure often only present in embryonic development
What is the endostyle?
Thickening of ventral region of pharync that generates mucus for feeding in primitive forms and the thyroid in adult mammals
T/F: Terrestrial chordates maintain their gill slits throughout their entire life
False: they are only present in embryonic development before disappearing
Describe water/food movement through subphylum Chephalochordata
Water -> gill slits -> atrium -> out through atrial slits
Atrium = cavity enclosing digestive tract
Describe water/food movement through subphylum Urochordata
Water enters via incurrent siphon -> pharyngeal slits -> atrium -> out through excurrent siphons
Atrium = cavity enclosing digestive tract
What does the paedomorphosis hypothesis for vertebrate evolution describe?
The retention of juvenile structures in adult form
Describe the evolution of jaws and paired fins
Derived from gill arches
Counter-current exchange is to do what
Permits transfer of solutes - especially oxygen - across membranes
How do freshwater fish control their salt/water balance?
Don’t actively swallow water
Kidney actively reaborbes NaCl while filtering lots of water
Large amount of dilute urine
How do saltwater fish control their salt/water balance?
Drink seawater
Reduced/absent golerulus
Kidney and gills secrete salts
Small volume of urine, highly concentrated
