Chordata Flashcards
what evolutionary path did they take and most of them are what?
.path of deuterostomes (anus then mouth)
. most = vertebrates
key points of chordata evolution
. cranium
. head wth big sensory organs
. columna vertebralis
. neural crest
.chroda
. neural tube
. postnatal tail
. blastopore becomes anus
. Pharyngeal slits
. flagellum on back of cell
what are the 6 characteristics
- Neural tube
- Notochord
- pharyngeal slits
- Postnatal tail
- Segmentation
- Thyroid gland
what are pharyngeal slits
Earliest feature - og func to filter waterfrom mouth + trap food particles
(POuches) connects pharynx with outside gills in sharks + fish.
disappears in animal embryos except the Eustachian tube (connects throat + mid ear)
what are the thyroid gland
(or endostyle)
groove which secretes mucous substance (contains iodine from seawater) to trap food particles
Hormones regulates metabolism + development
what are the notochord
flexible rod on dorsal side of gut . in vertebrates its displaced after embryonic dvlpmnt by vertebral column (forms round nerve cord) due to notochord only supports small body.
. Remnants of it is nucleus pulposus in mid intervertebral discs
. secretes molecular signals for differentiation + migration of other cells + directs formation of nervous system. (embryonic induction)
what is the postnatal tail
present in embryo but some chordates lose it after. regresses into tailbone in humans.
in chrodates notochord, neural tube+ muscles continue beyond anus + forms tail.
. main locomotary organ of aquatic chordates + balance organ fro terrestrial vertebrates.
what is neural tube
in vertebrates it differnetiates into brain + spinal chord.
located dorsallyin chordates
it is a fluid filled cavity that ensures nervous system has its own internal fluid envirmoment.
neuraltaion is after gastrulation
. ectodermal cells elongate + form neural plate then transfprms to neural groove. its walls grow dorsally + forms the tube
. its cavity makes central canal of spinal cord, filled with cerebrospinal fluid.
what is the neural crest
Derives from lateral edges of neural plate.
During neuralation they produce dorsally + come close to fuse + forms neural tube.
Also forms neural folds.
. The neural crest migrates to generate many differentiated cell types.
. In vertebrates soon after NC formation its cells become mesenchymal. these later differentiate to form various structures like visceral skull cartilages.
whats the subdivisions of mesoderm.
. axial - chordamesoderm, forms notochord
. paraxial - flanks the notochord + neural tube
. intermediate - located laterally
. lateral plate - located ventrally
lateral plate of mesoderm splits into 2 sheets:
*outer = somatic mesoderm (forms dermis in ventral part body)
*inner - visceral/splanchnic mesoderm (lines bod cavity from inside + forms eg circulatory systm)
what are somites subdivided into
- dermatome - forms dermis in dorsal part body
- myotome - forms skeletal muscles
- sclerotome - forms vertebrae + ribs of vertebrates.
Aquatic verts, myotomes persist in adult as muscle segments
how is cartilage created
*** dont acc know
cartilage in cuttlefish + horseshoe crabs revea commonalities with chordate chondrocytes, suggesting common evolutionary origin.
Origin + evo of mineralised skeleton
verts hv 2 sets of skeleton like hard structures:
- exoskeleton (dermal skull armour, teeth, scales, fin rays…)
- endoskeleton ( neurocranium, vertebra..)
endoskeleton has:
. endochondral bones formed by cartilage + replaced by miniralized bones.
. dermal bones that dvlp in dermis only by membranous ossification.
bony fishs retain exoskelton structores. terrestrial evo, hard structures are reduced.
What is the thyroid gland known as in chordates
endostyle
groove that secretes mucous substance to trap food particles
