Lesson 5 Flashcards
origin of jaws
number one most important evolution in vertebrate history
uses of jaws
- can facilitate breathing
- grasping prey
- chewing food - breaking it into tiny particles
- defense
- manipulating things
- movement of vocal tract
earliest existance of vertebrates
myllokunminga
- from early cambrian
- dorsal fin is more derived than the dorsal fin in lamprey
- know that the fossil has a notochord so it is at least a chordate
clues that the moyllokunminga was a vertebrae
- paired sensory structures in the head
- can infer from ^^^ that it had a neural crest
- ^^ can’t see the neural crest cells - can infer based on paired sensory structures and the cranium
- W shaped myomeres
conodonts
- not sure where they branch off from
- not sure if they broke off before the cyclosomes or not - about 4 cm long
- extinct
- lack pharyngeal slits
- myomeres have V shape, not W shape
environment during early vertebrate evolution (an abundance of extractoderms)
jawless forms of osteognathostomes
environment during early vertebrate evolution (mor likely to be freshwater or marine)
- vast majority of experts feel most likely from marine origins
- earliest fossil from marine deposits
- earliest known specimiens are all in marine deposits
- all invertebrates, chordates, as well as all deuterstomes that are not vertebrate are marine
t/f: all extant deuterostomes except the vertebrates are marine
true?
deuterostomes
anus forming before mouth
collecting evidence for marine animals coming first
!!!!!
- the ability of the modern kidney to excrete excess water
- the need to do so would be more important for a saltwater organisms
- suggesting that it is very old because the kidney is amazing at what it does
agnathans
- jawless vertebates
- lack jaws and 2 sets of faired fins
- lack specilized reproductive groups
hagfishes
- do have neural crests
- distributed worldwide
- marine
- deep sea dwelling
- often found in cold water
- individuals are not wide ranging –> live and breath very locally
- range –> singal individual
- disribution –> hagfishes as a group
- scavangers
- ## very good olfaction for detecting dead things
if hagfishes have no jaws, how will they bite dead animals
- gets a hold of the flesh and ties its posterior region in a knot
- tightening of knot helps to tear off fish
hagfish slime
glands - predtor deterrent
hagfish populaiton
sex ration of 100 females to 1 male
- might be hermaphroditic
unfortunately humans are hurting hagfish – eel skin
lamprey
- about 40 species, 2 genus
- most are parasitic on other animals
- attaches to a live fish and feed off its blood – secrets an anticoagulant so the blood doesn’t stop flowing
- found in many types of salinites
how are lamprey similar to salmon
- ascent freshater streams to spawn and breed
- young lamprey will swim out to the salt water
- anadromous (like salmon )
anadromous
migrating up rivers to spawn
lamprey (title ventilation)
- spend a lot of time in suction
- how will it ventiliate if it cannot open its mouth to breathe?
- doesn’t have flow through ventilation —–> have title ventilation
MEANING - almost like the flow of air in out lungs
- blind respiratory tube
- water is pumped through the gills – gas exchange occurs – then it is pumped back through the gills
what might have driven extractoderm to extinction
- never evolved jaws – were simply outcompeted by those with jaws
- if you look at phylogeny dats – notice that extracoderms coxisted with jawed fish for a pretty long time so notion has casted doubt on the previous hypothesis^^
- new ONE –> sea levels lowering and loss of habitat that extractoderms perferred
- obligates of coastal marine habitat
how did jaws evolve
evolved out of gill arches (we think)
- look at ancestral agnathous (jawless) - gnathostome look very similar – looks as though the first gill arch formed mandible and upper jaw
what did the 2nd gill become
hyoid arch
nostril
- presence of single nostril instead of 2 might have played a very evolutionary role in the formation of jaws
- anterior position of nasal placodes
- in jawed organisms - are anterior to () which leave space for neural crest cells
in a single nostril
there is no room for the neural crest cells to go to form the jaws
because of the presence of jaws, organisms have
- a true stomach
- a more complex rib
- distinct pancreas
why is having a true stomach, more complex rib, and a distinct pancrease associated with having jaws
- jaws open up many opportunitis –> diet choices
- paved the way for a more active lifestyle that required more energy
- NEED to FUEL
- a more complex skeleton is needed to sustain a more comlpex lifestyle
origin of fins
- acanthodians had structures similar to fins that aided in the movements of pitch, roll, and yaw
