1. Chordata All Chordates have 4 unique and very
specific characteristics:
Notochord- Supportive rod extending the dorsal length of the body.
Pharyngeal Slits- Series of slits in this region between the digestive tract and exterior. (filter feeding)
Dorsal nerve cord- Nerve cord running along longitudinal axis.
Postanal tail- Tail extending beyond anal opening.

3. Section 1: Early Chordates & Fish
Subphylum Urochordata (tail + cord)
Sea Squirts (Tunicates)
Sessile as adults
Respond to external stimuli but no complex
nervous response

4. Video

5. Monoecious- Adult contains both male and female
gametes.
Self- fertilization does occur but is rare.

7. Subphylum Cephalochordata (head + cord)
Lancelets
~45 species
Up to 5cm long
Distinct features
include 4 characteristics of a chordate.

8. Spends a majority of it’s time burrowed in sand, filter feeding.
Dioecious- male and
female gametes on
separate organisms

10. Cephalochordata
Urochordata
Vertebrata
Endoskeleton
4 chordata traits

12. Subphylum Vertebrata
Development bony vertebrae to replace the notochord.
Increased fossil record of this group
More distinct cephalization
Anterior skull develops to enclose brain.

13. Jawless fish were among the first vertebrates.
~500 mya
Developed into “true fish” and eventually into
terrestrial vertebrates.

14. Class Osteichthyes (bone + fish)
Any fish that has at least some bone
~20,000 species
Freshwater or marine

15. Locomotion Fish have a streamline body with scales
Excrete fluids that reduce friction as they move
through the water.

17. Gas exchange & Respiration
Gills-aquatic respiratory organ found in fish
Ram Ventilation-movement of water across the
gills by swimming with mouth open.

18. Maintaining the proper balance of water and
Osmoregulation
Maintaining the proper balance of water and
ions (electrolytes) in their tissues.

19. Freshwater- Environment has lower salt concentration.
Water wants to enter tissue.
These fish never drink. Only while eating.
Obtain salts(ions) from food
Produce high quantities of dilute urine.
Marine- Environment has high salt concentration
Water wants to leave tissue.
Drink water
Excrete salts through tissue
Produce concentrated urine