Lec 5: Jawless fish, amphibians Flashcards
Craniates
“chordates w/ a head” (animals w/ skull) neural crest develops into front part of skull (sensory) well developed brain (larger) increase in behavior complexity, increased metabolism, 2 chambered heart (all fish) and hemoglobin like blood pigments
Myxini (hagfish) - most primitive class (most ancestrally similar)
“Slimefish” Use slime as defense mechanism, scavengers, jawless. One of the most primitive forms of craniates
Vertebrates
Craniates w/ vertical column (spine) cranium (skull) greater support (fins)
Most primitive vertebrate class
Petromyzontida. Lampreys, jawless fish, parasitic, sucker mouth used for fluid feeding thru other fish
Gnathostomes
Vertebrates w jaws, calcified teeth, enlarged forebrain (enhanced smell/vision) lateral line (sensory sys that detects pressure waves/movement in water)
450 MYA
Gnathostomes appear (Silurian period)
Most primitive class of Gnathostomes:
Chondrichthyes. Sharks, rays, *cartilage based skeleton, placoid scales (rough scales used for reducing drag thru water) predators
Osteichthyans (bony fish)
Gnathosomes w/ calcified endoskeleton, swim bladder (gas filled organ for buoyancy) operculum (flap to protect gills)
Class actinopterygii
Ray finned fish, swim bladder, bony skeleton, ctneoid scales (overlapping)
400 MYA
Appearance of ray finned fish (Actinoypterygii) - Devonian period
Class Sarcopterygii
Lobed finned fish, fleshy fins, muscularized pelvic/pectoral fins. Coelacanths (group that resembles limbs of tetrapods) and lungfish (group that has aerial respiration and can live in low oxygen environments) **the form capable of invading land “walking” (most primitive class)
Tetrapods
4 limbs, digits, neck (head/body move independently) **Tiktaalik: link between lobe finned fish/tetrapods, showed evolution of carpel bones (wrist)
365 MYA
Tiktaalik transition from aquatic to terrestrial life (devonian period)
Order Urodela
Salamanders
Order anura
Frogs
Order apoda
Caecillians (legless, worm-like)
Class Amphibia
most primitive class of tetrapods. 3 chambered heart, respiration thru lungs/skin, tied to water (susceptible to desiccation (drying out)) Lay eggs in water (reproduction)
