Biology 124 SI
Chapter 34
1. What are the four chordate characteristics?
Presence of a notochord, doraal hollow nerve cord, muscular post anal tail with muscle
segments called (soma) and pharyngeal gill slits.
2. Where is the notochord located in humans?
Intervertebral discs
3. What did the dorsal hollow nerve cord become in humans?
Spinal cord
4. What happened to the gill slits and muscular post-anal tail in humans?
Humans start with a tail and with gill slits, but during embtyonic development the tail is
reabsorbed and the gill slits are altered to form parts of the ear and neck while lungs develop.
5. Describe the characteristics of a lancelet. How many of the cordate characteristics does it have
as a larva? How many does it have as an adult?
It has all characteristics as a larva and as an adult. This is a suspension feeder. It takes water in
through its mouth where ciri are to sift through the food, then the water enters the atrium of
the animal where it is filtered through the parangeal slits and the food particles pas through the
rest of the digestive tract while the water is sent to the atria, and it then leaves through the
atrial pore. This prevents excess water needing to pass through the digestive tract. This animal
has no vertebral column, no jaws, and no legs.
6. What animal was mentioned as belonging to Urochordata? What chordate characteristics does
it display as a larva and as an adult?
The tunicate (or water squirt). Larva has all 4 characteristics. Adult only has pharangeal slits. It is
sessile, and suspension feeding. It has an incurrent siphon where water enters the animal, and
food particles are gathered through the filter, and the water is ejected through the excurrent
siphon. It can also jet water at its predators for defence.
7. What trait arises with class myxini?
A cartalagenous skull, so we are now in craniates. These also have neural crest cells. Neural crest
cells must be present for something to be a craniate.
8. Where and when do neural crest cells arise?
During embryonic development during neurlation, the neural crest cells are extra cells that form
between the notochord and the developing neural tube. They then go to form parts of the face
and skull.
9. What are some other characteristics of craniates?
They have a high metabolism, they have a heart with at least 2 chambers, and they have closed
circulatory systems. They have red blood cells with hemoglobin, and they have real kidneys.
10. Give an example of an animal from myxini.
The hagfish. They have a cartilaginous skull and an axial rod of cartilage derived from the
notochord. They lack jaws and vertebrae, and have small brain, eyes, ears, and tooth like
formations made of keratin. (so not real teeth) They are marine bottom dwellers and
scavengers.
11. What are fibrous proteins usually used for? Are they soluble or insoluble, and give an example.
Structure or support in function, insoluble, keratin, cartilage, and elastin
12. What are globular proteins usually for, are they soluble or insoluble, and give an example.
Functional, soluble, and hemoglobin.
13. What is special about petromyzontida?
First presence of vertebral column and skull. They are the first vertebrates.
14. Describe an example from petromyzontida.
Lampreys, they are mostly marine, have heads and keratineized teeth. No jaws. They are
predators that attach to fish and suck their blood. They have a cartilaginous skeleton.
15. What is the meaning of gnathostomes and agnathostomes.
Gnathostomes have a jaw, and agnathostomes don’t have a jaw. This means that everything we
have talked about today is a agnathostome.