Chordata Flashcards
What characterizes the phylum Chordata?
4 anatomic features
What does studying invertebrates in Chordata allow for?
Clues to the origins of vertebrates
What are the 3 subphyla of the phylum Chordata? Examples
1- Urochordata = tunicates
2- Cephalochordata = lancelets
3- Vertebrata = vertebrates
What are the 4 common features that all Chordatas have at some stage in their life?
1- Notochord
2- Dorsal hollow nerve cord
3- Pharyngeal slits
4- Post-anal tail
What is the notochord? When is it present? Where is it?
Present in all chordate embryos
Longitudinal, flexible rod
Between digestive tube and nerve cord
What is the notochord made from?
Large fluid-filled cells in stiff fibrous tissue
What does the notochord do?
Skeletal support
What does the notochord turn into in humans?
Gelatinous (Jelly) material of the disks between vertebrae
How does the dorsal hallow nerve cord develop?
In embryo - from plate of ectoderm that rolls into a tube
What does the dorsal hollow nerve cord develop into?
Central nervous system = brain and spinal cord
Where are the pharyngeal gill slits found? (3)
Connected to the pharynx, behind the mouth and to the outside of the animal
What does the pharyngeal gill slits do?
Allows water to enter mouth and exit without going through digestive tract
What does the pharyngeal slits function as in invertebrates of Chordata?
Suspension feeding devices
What does the pharyngeal gill slits turn into?
Slits and structures become - modified gas exchange (water vertebrates), jaw support, hearing and more
What is the post-anal tail?
Muscular tail that extends past the anus
What does the post-anal tail contain?
Skeletal elements and muscles
What does the post-anal tail do?
Pushing force for aquatic species
What is an example of the subphylum Urochordata?
Tunicates = sea squirt
Where are Urochordata found? How do they move?
Marine - sessile
How do Urochordata feed?
Suspension-feeders
Explain the process of suspension-feeding for Urochordatas
Water passes inside animal by
incurrent siphon -> gill slits -> ciliated chamber (atrium) -> food is trapped here -> water exits through excurrent siphon
What are Urochordata encased in?
In a tunic of cellulose-like carbohydrate
What of the 4 characteristics of Chordata are seen in young and adult Urochordata?
Young - all 4
Adult - only pharyngeal gill slits retained
What is an example of Cephalochordata?
Lancelets
What of the 4 characteristics of Chordata are seen in young and adult Cephalochordata?
Young = all 4 Adult = retain all 4
How do Cephalochordata feed? Explain
Suspension feeders - mucus nets across gills trap particles