BIO Exam 4: Hemichordates and Early Chordates

Why were species in the Phylum Hemichordata originally thought to be Chordates?

they have gill slits, dorsal nerve cord, and notochord

What kind of feeders are Phylum Hemichordata?

deposit feeders

What is the embryonic development of the Phylum Chordata?

triploblastic, deuterostomes (radial cleavage), enterocoely

True or false: The Phylum Chordata is a single phylum

True

What species are included in Phylum Chordata?

lancelets, fishes, amphibians, reptiles, birds, and mammals

What type of symmetry does the Phylum Chordata have?

bilateral

What are the 5 distinctive traits of the Phylum Chordata?

1. Notochord

2. Dorsal hollow nerve cord

3. Pharyngeal slits

4. Postanal tail

5. Endostyle (thyroid gland)

What are the characteristics of the notochord?

• flexible rod, first appear in embryo

• replaced by vertebrae in most

What are the characteristics of the dorsal hollow nerve cord?

• sits dorsal

• enlarges to form brain

What are the characteristics of the pharyngeal slits?

• connects to outside

• developed for filter feeding, then gills

What are the characteristics of the postanal tail?

• evolved for locomotion in water

What are the characteristics of the endostyle (thyroid gland)?

• filter feeding with mucous

What is the distinguishing trait of Chordata? What function does it provide?

Notochord: supports and stiffens the body, acts as a base for trunk muscles, and provides axis around vertebral column develops

What are the characteristics of Subphylum Urochordata?

tunicates, both sessile and free-living forms, only the larvae have all 5 chordate traits, space dominated by the pharynx

What are tunicates?

colonies

What are the characteristics of Subphylum Cephalochordata?

burrow in sand, notochord extends to head, all chordate traits are present, segmented trunk, bilaterally compressed