what does diffusion require?
What is the fish gill designed for?
gas exchange in water
What are the closest relatives to the phylum chordata?
- phylum echinodermata (star fish)
what makes up the deutrostoma?
chordata, hemichordata, echinodermata
why is the phylum hemichordata considered closely related to the chordata?
they share pharyngeal gills
what is the phylum echinodermata?
marine deuterostomes with radial symmetry as adults, bilateral symmetry as larvae
what are the 3 subphyla of the phylum chordata?
Urochordata, cephalochordata, vertebrata
5 characteristics of chordates
notochord dorsal, hollow nerve cord pharyngeal slits postanal tail endostyle/thyroid gland
describe the structure of the notochord
- dorsal to gut tube and ventral to the nerve cord
what is the function of the notochord?
what takes over the function of the notochord in more recently evolved species?
the vertebral column
how is the hollow nerve cord formed?
formed by invagination of the surface cells in embryo
true or false: the neural tube is dorsal to the gut tube
true
describe the structure and location of the pharyngeal slits
What is the function of pharyngeal slits in aquatic species
slits and pouches create water current between mouth and pharynx for feeding and respiration
What is the function of pharyngeal slits in terrestrial species
transient embryo structures and slits not opened in pouch all
describe the structure of the postanal tail
located posterior to anus
what is the function of the postanal tail?
swimming
describe the structure of the endostyle
granular groove on the floor of the pharynx
what is the function of the endostyle
what is the endostyle an early version of
the thyroid gland
What era were the oldest vertebrates found?
early Cambrian (540 mya)
what are the 5 major innovations of vertebrates?
what is the head derived from?
neural crest cells and ectodermal placodes