Please enable JavaScript.
Coggle requires JavaScript to display documents.
A220 - Coggle Diagram
A220
Chondrichthyes (Cartilaginous fish)
about 750 extant species
2 subclasses
Holocephali
Ratfish & Chimera
Around 34 species
Most are deep water inhabitants
oviparous
holostylic jaw suspension
operculum covering 1 pair of gills slits
bottom feeder
crustaceans
molluscs
united teeth (crushing plates)
fins
fin rays
1 ventral fin
2 dorsal fins
elasmorbranchii
Sharks (selachimorpha)
Galeomorphii
Squalomorphii
rays
skates (Batoidea)
Characteristics
monophyletic group of fish due to shared common evolutionary ancestors and distinctive characteristics that set them apart from other fish groups.
jaws and 2 pairs of fins
Flexible cartilaginous endoskeletons not replaced by bone
placoid scales (tiny tooth like scales)
Teeth aren't attached to jawbones but embedded in flesh, allowing for continuous development in rows, moving forward to replace lost teeth.
gills for gaseous exchange
seperate sexes and internal fertelization
male have claspers to transfer sperm into females
modes of reproduction
Oviparous
give birth by laying eggs
Ovoviviparous
eggs incubate and hatch inside the mother's body and babies are born
viviparous
young develop inside the mother's placenta and are born live
Subclass Elasmobranchii (sharks and rays)
key characteristics
over 1000 species
5-7gill openings
rigid dorsal fins
upper jaw is not fused to their skull
lack swim bladder but have large livers that are full of oil to provide buoyancy
Superorders
Galeomorphii (shark)
Largest living vertebrate other than whales
Most are predatory while some are filter feeders
shorter digestive tracks
Complex brains with a spinal cord protected by vertebrate
Reproduction modes include Oviparous, Ovoviviparous, viviparous
Acute senses
Sharp vision
electroreceptors
lateral line system
nostrils
Adaptations for swimming
Streamlined body
powerful swimming muscles
Dorsal fins that functions as stabilizers and pectoral fins that provide lift
Large amount of oils and fats in liver provides buoyancy
Continuous swimming for gas exchange
Squalomorphii (squalean shark)
About 157 species
Mostly found in cold, deep waters
1 or 2 dorsal fins
may or may not be proceded by spine
lacks anal fin
some species may be dorsoventrally flattened
Zones they are found in:
Mostly benthic zone
few found in:
mesopelagic
bathypelagic
Batoeidea (Rays, and skates)
dorsoventrally flattened body shape
small dorsal and caudal fins
whip-like tail and some having venomous barbs on the tail to act as defense mechanism
Rays give birth to young while skates lay eggs
feed by using jaws to crush mollusks and crustaceans