Phylum Chordata - 5 Important Hallmarks

We have moved on to Phylum Chordata but before studying the characteristics of this diverse group make sure you are able to draw a phylogeny including all of the following:

Animalia (Metazoa)
Protostomia
Deuterostomia
Echinodermata
Asteroidea
Holothuroidea
Crinoidea
Ophiuroidea
Echinoidea
Chordata

After placing each of these group names at a node make a list of the unique characteristics for each node. An example would be under the node that contains Asteroidea you could list; madreporite on aboral side, podia contain suckers, open ambulacral groove. Hopefully you can do this activity without looking at notes or the book. If not do it again until you can.

*** If these characteristics seem foreign, you need to study more ***

5 Hallmark Characteristics of Chordata:

1.  Notochord - flexible, rod like structure that is replaced by a vertebrae in most vertebrates.
2. Dorsal Nerve Cord - dorsal to the digestive tract and hollow. The anterior end becomes enlarged to form the brain in vertebrates
3. Pharyngeal Slits (or Pouches) - slits evolved as a filter-feeding apparatus (still used for this in protochordates). Adaptations to this filter-feeding characteristic led to the evolution of a respiratory organ (internal gills) in aquatic vertebrates
4. Endostyle - secretes mucus that traps small food particles brought into the pharyngeal cavity. In ancestral chordates, endostyle and perforated (slits) pharynx work together to create an efficient filter-feeding apparatus. The thyroid gland in chordates is derived from the endostyle.
5. Postanal Tail - this tail along with muscle and stiffening of the notochord provided the motility for chordates. Its efficiency is later increased in fishes with the addition of fins.