what is a shark? Flashcards
how long have sharks been around?
sharks date back to the Devonian times
class Chondrichthyes - what happened to the endo skeletons?
bones were absent from the cartilaginous endoskeleton
prismatic calcification of surface layers of cartilage matrix
bones in teeth and scales
what is a clade?
a defining character
why is shark skin rough to the touch?
placoid scales or dermal denticles
what are placoid scales?
form in dermis
project through the epidermis to surface
tooth-like structures:
enamel tip
dentin
pulp activity
what is special about the dogfish teeth and scales?
homologous structures to the placoid scales
what type of teeth do dogfish have?
tooth whorls - spirally arranged clusters of the individuals’ teeth
what are the characteristics of dogfish mouth?
the ligamentous band along the jaw
cartilage beneath flesh
developing teeth in the file behind each functional tooth
tooth replacement occurs weekly in young shaks
what is cranial kinesis in sharks?
the upper jaw can unhinge and extend, protruding outwards
how does cranial kinesis work?
hyostylic jaw suspension
cartilage - firm but movable attachment to the cranium
elastic ligament- allows protrusion of the upper jaw
how do sharks breathe?
ram ventilation:
when the shark is moving - water comes in via the mouth - out via the gills
5-gill pairs in most sharks and rays
buccal pumping:
sharks at rest - water in via mouth and spiracles
- out via gills
flap valves - no water in via gills
what is ram ventilation?
when the shark is moving - water comes in via the mouth - out via the gills
5-gill pairs in most sharks and rays
what is buccal pumping?
sharks at rest - water in via mouth and spiracles
- out via gills
flap valves - no water in via gills
how do filter feeders eat?
gill filaments contain gill rakers which
how have filter feeders evolved?
they have evolved independently in 3 shark species
