Bio 108 topic 26

What clade do chordates belong to?

Clade Deuterostomia.

Which animals are in Phylum Chordata?

All vertebrates, plus urochordates and cephalochordates (invertebrates).

Do all chordates have backbones?

no, only vertebrates do; urochordates and cephalochordates do not.

What is the notochord?

A flexible, dorsal rod for skeletal support; forms from dorsal mesoderm.

What is the dorsal hollow nerve cord?

A nerve cord that forms from ectoderm; it runs dorsally and is hollow.

What are pharyngeal slits or clefts used for?

• Invertebrates: filter feeding.

• Vertebrates (except tetrapods): gas exchange.

• Tetrapods: develop into parts of the head and neck.

What is the post-anal tail?

A muscular tail extending beyond the anus; used for movement in many aquatic chordates.

What type of body plan do chordates show?

Segmented, at least in embryo (e.g., muscle blocks, vertebral column).

Cephalochordata (Lancelets):

• Resemble small fish.

• Retain all chordate traits as adults.

• Filter-feed: water enters mouth → mucus-covered pharyngeal slits trap food → exits via atriopore.

Urochordata (Tunicates):

• Marine filter-feeders (sessile or pelagic adults).

• Larvae show all chordate traits.

• Adults lose most traits; use pharyngeal basket to filter food with mucus.