Phylum Chordata

SDC characteristics

1. notochord

2. hollow, dorsal nerve cord

3. pharyngeal slits (pharynx w/ slits)

4. post-anal tail

5. endostyle

notochord

runs down the dorsal portion of the body, homologous to intervertebral disk that cushion the vertebra of the vertebral column

hollow dorsal nerve cord

tube that runs dorsal to the notochord

pharyngeal slits

• In lower chordates its’s referred to as the pharyngeal basket and is a site for filter feeding and gas exchange, and is supported by gill bars

• In aquatic jawed vertebrates, it gives rise to gills and is used for gas exchange

• In jawed vertebrates, it has been modified into homologous structures, including the jaw and ear bones, tonsils, and the thymus gland

post-anal tail

used for locomotion

endostyle

• produces mucus in lower chordates, that coats the gill bars and used for filter feeding

• in vertebrate chordates, has been modified and is homologues to the thyroid gland

myotomes

most chordates have segmented muscles that occur in blocks

subphylum Urochordata

tunicate; adult form lacks many of the phylums 5 SDC but the larva still exhibit the characteristics. includes 3 classes, one planktonic, one sessile, and one pelagic

adhesive papillae

used to anchor larva onto substrate to metamorph into adult form

visceral cavity

contains the stomach, intestines and gonads

tunacates

monoecious, open circulatory system

tunic

tough coating that surrounds the body of the tunicate

tunicin

modified cellulose polysaccharides that is apart of the tunic

subphylum Cephalochordata

lancelets, demonstrate all 5 of the phylum SDC; also show beginning of a ventral heart and segmented muscle, diecious. closed circulatory system

caudal fin

tail fin

atriopore

where water from the internal atrium exits the body of lancelets

myosepta

walls

adult tunicate digestion

food enters the esophagus, through the septum into the visceral cavity to the stomach. stomach is the site of digestion then to the intestines where nutrients are absorbed and undigested waste go to the rectum which passes through the septum into the atrium then passed out through the anus. feces is deposited from the anus to the atrium closes to the excurrent canal to be removed from the water

velum

thin vertically oriented membrane that surrounds the true mouth of lancets

hepatic ceacum

homologues to vertebrae liver, site of chemical digestion for ancelets

subphylum Vertebrata

Possession of segmented vertebrae, which replaces the notochord, possession of a cranium that surrounds the brain, a closed circulatory system, and a distinct heart. smaller pharyns and a smaller number of gill slits. highly cephalized

• class Agnatha - jawless fishes

• class Actinopterygii

• class Sacropterygii

lampreys

specialized ectoparasites of other fishes. posses a rasping tongue, anadromous fish

ammocoetes larva

the larval form of lampreys

anadromous fishes

fishes that spawn in fresh water but mature in the ocean

Class Actinopterygii

ray finned fishes, characterized by the possession of a bony skeleton and gill slits covered by operculum

swim bladder

gas filled chamber in bony fishes used to manipulate internal density to control buoyancy

operculum

protects the gills and opens and closes to ensures that water flows through the pharynx and gills in a one way direction

nairs

external feature, for smelling

lateral line system

a groove that includes many pores that lead to hair cells, which are sensitive to mechanical disturbances in the water which allow for fishes to sense splashes and other movements from predators and prey.

cycloid scales

rounded

ctenoid scales

square w/ jagged edge on one side

peritoneal cavity

abdominal organs

pericardial cavity

hold the heart

parietal peritoneum

lining of the peritoneal cavity wall

viceral peritonium

membrane that lines the organs

serous membrane

parietals and visceral membrane that serve to prevent organs from sticking to each other and to the walls

mesenteries

membranes that suspend internal organs and hold them in position

oviparous

lay eggs

ovoviviparous

live birth but fetus is nourished by egg yolk instead of placenta

viviparous

live birth from placenta

liver

produces bile

galbladder

stores bile

bile duct

delivers bile from the gallbladder to the duodenum

pyloric caecae

functions in chemical digestion

spleen

site of blood filtration

single circuit of blood flow in fishes and sharks

Gills to body to sinus venosus, then to atrium, ventricle, and conus arteriosus, returning to gills.

Class Chondrichthyes

cartilaginous fishes , characterized by the cartilaginous skeletons and exposed gill slits

claspers

serve as the copulatory organ to transfer sperm into females for internal fertilization

hair cells

sensory receptior cells

ampullae of lorenzini

electroreceptors that detect electrical currents

electrical sensory system

modification to the lateral line system for advanced sensory in cartilaginous fishes, uses ampullae of lorenzini receptors

oily liver in sharks

provide buoyancy

spiracles

modification of the gill slit associated with the anterior gill arch

spiral valve

increase surface area for absorption

pyloric sphincter

regulates food that passes from stomach to the intestines