chordates Flashcards
tow character states chordates have that are nit synapomorphies are?
bilateral symmetry and segmentation
the phylum chordata has four synapomorphies (shared derived characteristics), what are they?
- notochords
- dorsal, hollow nerve cord
- pharyngeal clefts
- muscular, post-anal tail
what is the notochord?
a flexible rod located dorsally between the digestive tube and the nerve cord that provides structural support and allows for muscle attachment
what is a chordata’s notochord made out of?
cartilage
how does the hollow nerve cord develop?
from the neural plate of the ectoderm
what does the chordates nerve cord turn into among vertebrates?
brain tissue, nervous tissue and spinal cord
in most chordates, the pharyngeal clefts turn into?
pharyngeal slits
what purpose does the pharyngeal cleft serve?
allows water entering the mouth to exit without continuing through the entire digestive tract
what do the chordates pharyngeal slits turn into for vertebrates?
gas exchange/breathing
in terrestrial vertebrates, the pharyngeal cleft does not turn into slits! what does it turn into?
jaw support and parts of the ear
what is the function of chordates having a post-anal tail?
provides propulsive forces in swimming and for balance as a rudder
the first group to diverge from the chordates is called the?
cephalochordata (lancelets)
what are some characteristics of landcelets?
segmented
minimal cephalization
sedentary suspension feeders
breathe through the surface of their body wall
what are hox genes?
a highly conserved (relatively unchanged) nucleotide sequence to has regulatory genes!
what are regulatory genes?
proteins that turn other genes on or off; they determine what genes to express
what did lancelets help scientists discover?
lancelets do not have a well-developed brain, but they have the same genes you would see in the brain of a well-developed vertebrate, meaning that the brain evolved from something similar to a lancelets simple notochord
following cephalochordata came..?
urochordata (tunicates)
in urochordata’s larval stage, they possess?
all four synapomorphies
tunicates undergo metamorphosis, meaning?
chordate characters begin to disappear
tunicates notochord is a ______________ characteristic?
homologous
chordates subphylum vertebrata posses what new structure?
vertebral column (backbone)
what is the vertebrata’s backbone replacing?
the function of the notochord
what does the backbone provide vertebrates with?
rigidity and attachment site for muscles and other skeletal elements, can grow against gravity, strength
chordates subphylum vertebrata also has hox gene duplication. what does this allow chordates to have?
more complex body structures
how many sets of hox genes are in hox gene duplication?
two or more
what two groups make up our jawless vertebrates?
hagfish and lampreys
what are some characteristics of the class myxini (hagfish)?
- skull and cranium composed of cartilage
- notochord
- tiny eyes that lack lenses
- protection by exuding slime from glands on the sides of their bodies. when it interacts with water, it expands
what are some characteristics of the class petromyzontida (lampreys)
- sucker like mouth with hooks
- single lens eyes
- skeleton is made of cartilage that is not mineralized
- skulls are incomplete but made of cartilage
- notochord is surrounded by a cartilaginous tube that partially encloses the nerve chord
what phylum includes fish with jaws?
gnathostomes
gnathostomes have two pairs of?
limbs or fins
gnathostomes had further duplication of ___ ______ which added?
hox genes which added genetic diversity
what traits did the duplication of hox genes allow in gnathostomes?
sensory characteristics, larger brains, jaws, vision, smell
how did jaws evolve?
modifications of two pairs of skeletal rods that had supported pharyngeal slits (skeletal rods began to move forward which allowed them to become larger and form into the jaw)
what did gnathostomes have some of their posterior slits specialized for?
gas exchange (gill slits)
the class chondrichthyes were some of the first early jawed fish; this included animals such as?
sharks, rays and chimeras
chondrichthyes had an ___________ made of cartilage and ____ teeth
endoskeleton, bony
chondrichthyes cartilaginous skeleton what what kind of character state?
derived!
development of most vertebrates occurs when..?
the skeleton is first cartilaginous and then becomes ossified (bony)
does all cartilage in chondrichthyes become ossified?
no!
what is the function of sharks, rays and chimeras nostrils?
only for smelling and capturing scent, not breathing
through chonrichthyes pores around their head, they are able to detect?
electrical signals emitted by their surroundings that are generated by muscular movement of other animals
sharks, rays and chimeras are able to detect vibrations in the water due to their?
lateral line
how do sharks reproduce?
sperm transfers through copulation (internal fertilization)
