Chordate Basics Flashcards
What are the 5 basic chordate characteristics?
perforated pharynx / pharyngeal gill slits
notochord
dorsal, hollow nerve cord
endostyle/thyroid
post-anal, muscular tail
T or F: every chordate, at every stage, has all 5 characteristics
false
the 5 characteristics are present at any life stage of all chordates
Describe perforated pharynx/pharyngeal gill slits
slits/holes in pharynx (posterior to mouth)
What is the major function of a perforated pharynx?
to allow water that has entered the animal’s mouth to leave without passing through the digestive tract
How is a perforated pharynx used in chordates?
for suspension-feeding
For what functions have perforated pharynxes been modified?
gas exchange (aquatic vertebrates, ex. fish)
jaw support
hearing
Describe the notochord
a skeletal structure between the digestive tube and nerve cord
elastic, laterally flexible, but composed of pretty stiff tissues
In vertebrates, which life stage is the notochord often present?
embryo
What does the notochord become in vertebrate adults?
remnants - ex. vertebral disks
Where is the dorsal, hollow nerve cord located?
dorsal to the notochord
What does the dorsal, hollow nerve cord develop from? develop into?
from: ectoderm
into: brain and spinal cord
What is the muscular, post-anal tail made of? what does it do?
made of muscular and skeletal elements
used for propulsion in aquatic animals
What is the endostyle/thyroid gland?
a ciliated groove in the floor of the pharynx used to trap food particles
thyroid glands metabolize iodine
What are the 2 invertebrate groups of Chordates?
Cephalochordata (lancelets/amphioxus)
Urochordata (Tunicates)
Which is the major genus of Cephalochordates?
Branchiostoma
What are two other names for Cephalochordates?
lancelets
amphioxus
What are the basic characteristics of Cephalochordates (lancelets)?
small
blade-like
retain chordate characteristics into adulthood
T or F: lancelets are the only chordates that retain chordate characteristics into adulthood
true
Compare the larval stage and adult stage of Cephalochordates (lancelets)
larvae: planktonic, feeding
adults: can swim, but mostly burrow
How do Cephalochordates (lancelets) conduct gas exchange?
across external body surface
What function do pharyngeal gill slits have in Cephalochordates (lancelets)?
used for filter-feeding
Describe Urochordates (Tunicates)
small
marine
sessile
suspension feeding
solitary or colonial
What are the distinguishing features of Urochordates (tunicates)?
body is fully enclosed in a tunic (composed of tunicin and other proteins)
U-shaped gut
endostyle present
ganglion nervous system
tubular heart can reverse direction of blood flow
What class do most tunicates belong to?
Ascidiacea
What type of chordate can reverse its blood flow?
Urochordates (Tunicates)
Compare the larval stage and adult stage of Urochordates (Tunicates)
larvae:
tadpole
short-lived
non-feeding
tail with notochord and dorsal hollow nerve cord
adults:
no notochord, nerve cord, or tail
Describe reproduction in Urochordates (tunicates)
individuals are hermaphroditic (one ovary, one testis)
reproduce tadpole larva
T or F: adult Urochordates (tunicates) look very similar to larvae and retain many of the chordate characteristics
false
they look very different and have lost the tail, nerve cord, and notochord
retain pharyngeal slits for filter feeding
Which of the basic chordate features do humans retain as an adult? which are modified?
lost:
post-anal tail
retained:
endostyle = thyroid
nerve cord = brain and spine
notochord = vertebral disks
gill slits = jaws, ear bones
What are the major advantages for paired pharyngeal gill slits?
allows filter feeding - not everything sucked into the mouth goes through the digestive tract
allows external gas exchange
What are the major advantages for brain and dorsal nerve cord?
to sense and navigate and respond to environment
What are the major advantages for segmented muscles?
for movement to catch prey and avoid predators
to navigate environment
What are the major advantages for the notochord?
structural support
What are the major advantages for post-anal tail?
for movement, especially if aquatic, to use as a propulsive force
for balance on land
What are the major advantages for endostyle or thyroid?
endostyle assists in filter feeding
thyroid assists in iodine metabolism
