1. Higher Chordates: Fishes & Amphibians
Chapter 34

2. Phylum Chordata

3. Recall: Subphylum Urochordata Subphylum Cephalochordata Class Myxini
Tunicates
Subphylum Cephalochordata
Lancelets
Class Myxini
Hagfish
Least derived craniate lineage still surviving
Chordates with a head

4. Subphyla Vertebrata Endoskeleton Closed circulatory system
Vertebrae: bone or cartilage
Closed circulatory system
Single well developed heart
Skull with a brain
Anterior to the spinal cord
Extinct vertebrate:
Conodont

5. Class Agnatha Jawless fish Lack paired fins, scales
Ostracoderms
extinct
Cyclostomes
Lampreys, hagfish
Lack paired fins, scales
First organisms with a backbone
Appeared 500 mya

6. Class Acanthodia Spiny fish Developed jaws with bony edges
Gnathostomes
Internal skeletons of cartilage
Extinct
Appeared 430 mya

7. Class Placodermi
Fish with massive heads
Extinct
Appeared 410 mya

8. Class Chondricthyes Cartilage fish (bone in teeth & scales)
Sharks, skates, rays, ratfish & chimeras
Appeared 400 mya

9. Chondricthyes characteristics
Premier Predators
Streamlined body (power, not grace)
Oil bladder (buoyancy)
Acute vision (but colorblind)
Detect electric fields

10. Chondricthyes characteristics
Reproduction (variety)
Oviparous
lay eggs externally
Ovoviviparous
keep eggs in uterus until hatching
Viviparous
Placenta – live birth

11. Class Osteichthyes Ossification of the skeleton (Bone)
Draw H2O across gills
Operculum bony covering
Swim bladder (buoyancy)
Mostly oviparous
Appeared 400 mya
95% of today’s fishes

12. Subclass Actinopterygii
Ray finned fish
Bony rays in fins for maneuvering, defense, and other functions

13. Subclass Sarcopterygii
Lobe finned fish
Rod-shaped bones in fins surrounded with thickened layer of muscle
Swim or “walk” across substrate
Actinista (coelacanth)
Dipnoi (lungfish)

14. Evolution of tetrapods
One of the most significant events in vertebrate history was when the fins of some lobe-finned organism evolved into the limbs and feet of tetrapods

15. Class Amphibia “Two lives” Gas exchange
aquatic larva develops into a terrestrial adult
Gas exchange
Lungs and moist skin
All amphibians must lay eggs in water

16. Order Urodela
Salamanders
tails

17. Order Anura
Frogs and toads
No tail

18. Order Apoda
Caecilians
Legless
Wormlike
Burrowing

19. Amphibian Metamorphosis