Lesson 6 Flashcards
internal fertilization
you don’t give live birth if you don’t have internal fertilization, but you can have internal fertilization and not have a live birth
placoderms
- covered in this thick boney shield
- ancestral of these were primarily marine, but some were form a freshwater environment
- pelvic fins
—distinct in modern condrichthiean
—males have clapers to internally fertilitze
——- internal fertilization suggests complex mating
extant clades of neoselachii *sharks and rays)
- sharks
- skates
- rays
- rabbit fishes
- ^^^^ living descendants of the entire radtiation of gnathostomes
^^^^ cartilaginous fishes
chondrichthyes
- cartilagineous fishes
- primary a freshwater group a longggggg time ago
- now –> mainly marine
- scales are possible remenant of dermal bone
- kind of like teeth – dentine
- constant string of replacement teeth when a tooth falls out
cladoselache
- mouth opening is terminal
- extinct chondrithye fish
- jaw support is not hyostylic – its anphostilic
- upper jaw is firmly attached to the chondochrnium
- body is only supported by a notochord
- basal elements anchor fin into place – not the mobility of a fin
- proabably pelagic predators (open ocean)
- lacked body scales and calcification to possibly increase bouyancy
damocles
- shark head with a clasper
- nuchal spine (only in males_ –> might be a sexually selective trait, we don’t know
helicoprion
no one knows how to arrange this fossil
– has a tooth whorl – teeth wrap into spiral
xenacanthus
- calcified cartilaginous skeleton
- bone vs. cartilage
- bone is vasularized – can remodel itself
– cartilage is not really healable
hybodus
- terminal mouth
- amphystylic jaw suspension
- heterodonts
- 3 basal cartilages supporting each fin
- triblastic fin attachment –> probably makes it more moveable
- claspers for courtship
heterodonts
different forms of teeth that serve different purposes
hybodus (heterocercal tail)
- caudal fin with 2 asymmetrical lobes
lobe on tail influenes swimming pattern – how it propels and generates lift - pterolepis had a hypochrodal tail
leading edge tail on tip
lift is upward right at the tail
leading edge of tail on bottom
- vertical component is downard
- lift is downward
evolution and radiation of extant sharks
- overhanging ventral position of mouth
- solid calcified vertebra
- sensory systems
sensory system of extant sharks
- neural masts of lateral line system
- ampulaie of lorrenzii (use electric fields to sense prey)
think about how you hear and can find out where things are – how do you know the direction of sound
– for sound that comes from the right, it takes longer for sound to reach the left ear
— interaural time difference
what allows you to identify location (sound detection –> similar mechanism in other vertebrates
if sharks are following an odor plume of a bleeding surfer, how do they know which direction the smell is coming from
there could be a time idfference between the odor hitting each nostril which could be used to identify direcion
^^^Hypothesis for what gives rise to the wide heads in hammer head sharks
disconnected skull bone movement: cranial kinesis
why it appears that sharks can kind of shoot their jaws out
true/fasle: internal fetilization is universal for sharks
true – they can lay eggs or have live birth
what kind of species is the shark
- K species
- only so much energy to go around
- no evidence of parental care in sharks
evidence of a social network in the tiger shark
- 2 individual sharks had acoustic receivers on them –> when they got close enough they sent a signal and were able to find out that some sharks have “friends” “bestfriends” and “mutual firends_
– fission and fusion behavior - social groups would undergo fission and fusion (thought to only occur in mammals)
fission and fusion behavior
describes the movement of social groups
life history traits
- life span
- annual mortality rates
- fecundity
- size at maturity
sharks life history
- sharks have a life history that does not allow for rapid population recovery
- huge fecundity difference
- many in danger - tend to cross international boundaries and it’s hard to regulate in more than one country