17. Agnatha and Sharks Flashcards
what are four important features of a craniate?
craniates are CHORDATES WITH A HEAD
have two clusters of hox genes (cephalachordates only have one)
has a neural crest allowing diversity
a heart with at least two chambers
what group is hagfish (most basal group of craniates) apart of and what are six features of it?
hagfish are known as myxini. they have
no jaw (gnthastomes) with teeth like projections - no real teeth
the notochord persists in adults
no paired fins
smooth skin
skelton and skull made of cartilage
what is a defining characeristic of vertebrates and what is their basal group?
vertibrates are craniates with a backbone! petromyzontida (lamphreys) are the basal group
what are five derived characteristics of vertibrates?
innovations in the nervous system
skull
jointed skeleton
fin ray in aquatic system
closed circulatory system
what are important characteristics of petromyzonida? four points
marine and freshwater
true skeleton
no jaws
notochord persists into adulthood
what is the lifestyle of a petromyzonida? two points
they are ectoparasites that drink blood
what are 6 types of clades that are gnthostomes?
bony fish
amphibians
reptiles
birds
mammals
sharks and rays
what is a defining character of a gnthastome?
vertebrates that have jaws
what is a chondrichthyan? four points
(con-drick-these)
cartiligous skeleton (not bone)
jaws
paired fins
scales and teeth
where did jaws evolve from (species name and when)
placoderms, 470 MYA. placoderms where the first jawed fish. jaws are beleived to have evolved from skeletal rods that previously supported anterior phanygeal (gill) slits
why are jaws so important?
the changed feeding behaviour from filtering to active predetation
whats the main difference between a placoderms and chimera jaw?
placoid have teeth made from placoid (which is the same as their scales) it sheds and regrows. chimera dont have teeth that shed, instead have three pairs of hard grinding tooth plates
how do chondrichthymes feed? three points
swallow prey whole or tear chunks off them
some have filter feeder lifestyles which evolved independantley
what do the scales, cartilage skeleton, paired fins, dorsal fins and trunk and tail do for locomotion
scales lower resistance
cartilage skeleton is very flexible
paired fins provide lift
dorsal fins as stabilisers
trunk and tail movement for thrust
what are importnat features of the senses of chondrichthymes? four points
colour vision
acute smell
electro receptors to detect electro field to navigate
low frequency vibrations
