An Introduction to the Vertebrates Flashcards
Agnathans
A small group of jawless vertebrates
- not a taxonomic group
- include much extinct or armoured fish (octraderms)
Cyclostomata
living groups include hagfish and lamprey
- look similar
Hagfish
- about 40 species
- feed on invertebrates or are scavengers
- skull but no vertebrae
Lamprey
- about 40 species
- feed on the fluid or blood of fish
- can cause problem to fisheries
- mouth designed for attaching, scraping
Gnathostomes
- all the other vertebrates that have jaws
Advantages of Gnathostome
Different food Resources
Defence
Other uses
Advantages of Gnathostome - Different food Resources
- grip becomes surer
- food can be broken down
- carnivory and omnivory
Advantages of Gnathostome - other uses
- digging holes
- holding mates
What does natural selection often tinker with?
Preexisting structures
Where did the pharyngeal arch originate?
in filter feeders, but these arches have a number of anatomical components that can be tinkered with muscle, bone, nerves and blood vessels
How did pharyngeal arches occur?
- first 2 arches lost
- 3rd arch modified into upper and lower jaws
- 4th arch (hyoid arch) supports the jaw
- subsequent arch modified (usually) for respiration
What were the opportunities that jaws opened up?
- fish were no longer limited to prey that were smaller than their mouths
- the small ones could also protect themselves from larger fish
Jaws diversified quickly, largely at the expense of the jawless fishes
What are Chondrichthyes?
- cartilaginous fishes
- skeletal is cartilaginous
- bone restricted to teeth and scales
- in most groups notochord replaced by vertebral column
- unique scale type
- variable development
- fertilization always internal
- development can be oviparous, ovoviviparous or viviparous
Placoid scales?
Provide tough but aerodynamic skin
Clasper of the male
- an intermittent organ
- delivers sperm
- modified pelvic fins
