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Flashcards in Zoology Test 3d Deck (50)
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Subphyla of Chordates

- Urochordates
- Cephalochordates
- Vertebrata


types of Urochordates

- tunicates or sea squirts


types of Cephalochordates

- lancelets or amphioxus


super classes of Vertebrata

- Agnatha
- Gnathostomata



- hagfish
- lamprey
- jawless vertebrates (primitive characteristic: came from jawless ancestors)


classes of Gnathostomata

- Chondrichthyes
- Actinopterygii
- Sarcopterygii
jawed vertebrates


types of Chondrichthyes

- sharks
- skates
- rays
- chimeras


types of Actinopterygii

ray-finned bony fish


types of Sarcopterygii

lobe-fined bony fish


five features of chordates

- notochord
- dorsal nerve cord
- pharyngeal gill slits
- postanal tail
- endostyle or thyroid gland


characteristics of notochord

- supporting structure of chordate body
- present in all life stages of primitive chordates
- present only in early stages of advanced chordates
- replaced by vertebral column during development of advanced vertebrates


characteristics of dorsal nerve cord

- dorsal, hollow nerve cors
- clusters of ganglia at anterior end of nerve cord (brain or CNS)


characteristics of pharyngeal gill slits

- outer ectoderm comes into contact with endoderm of pharynx and openings are formed
- original use was pharyngeal filter feeding, later, gills were added to arches between slits
- been retained and put to other uses
- forms jaws and inner ear; forms tonsils, parathyroid, thymus and eustachian tube


what are the arches?

supportive structure that lies between each gill opening


characteristics of endostyle/thyroid gland

- secretes mucus that traps small food particles brought into pharyngeal cavity
- secretes iodine-contianing porteins
- homologous to thyroid gland in vertebrates


characteristics of postanal tail

- tail extends beyond anus
- used in propulsion through water
- retains this function in many chordates, but is present in embryo of all chordates


characteristics of Urochordates

- "tunicata" because a covering ("tunic") containing cellulose surrounds body
- some species forcefully discharge a jet of water from excurrent siphons when irritated
- about 2000 species
- marine
- mostly sessile
- solitary, colonial and compound forms all occur, compound forms share single tunic
- closed circulatory system


why do tunicates have excurrent siphon?

they are pharyngeal filter feeders that pull water into basket-like pharynx via action of cilia
- water exits via the excurrent siphon


postanal tail in tunicates?

- free swimming larva posses all five chordate characteristics
- undergoes metamorphosis and loses tail and notochord, dorsal nerve cord reduced
- becomes sessile adult


characteristics of cephalochordates

- 2-3 inches long
- inhabits sandy bottoms of marine coastal areas around world
- anchors itself into bottom via tail
- filter feeds
- only 25 species
- have all five characteristics
- closed circulatory system
- sexes separate
- simple nervous system
- simple sense organs


feeding in cephalochordates

- water in mouth, then through pharyngeal slits
- endostyle produces mucus to capture particles
- water exits pharynx then leaves body thru atriopore
- food in mucus cord enters digestive tract


chordate evolution

- all current evidence points to fee-swimming creature as ancestral chordate, with sessile tunicates representing secondary condition


characteristics of vertebrata

- cranium (braincase)
- 3 part brain
- head with paired sense organs
- 2+ chambered heart
- other physiological changes to support high metabolism


characteristics of lampreys

- smooth, scaleless skin
- paired pectoral and pelvic fins are absent
- only have single dorsal fin
- notochord persists throughout development and present as main supporting structure in adult
- ventrally located circulatory system with two chambered heart


what is unique about lampreys?

- undergo metamorphosis from ammocoete larva to adult
- ammocoete larvae probably resembles ancient ancestor


feeding in lampreys

- some use their sucker-like moth to parasitize fish; can kill host because they don't stay long
- others eat vegetation


What is a fish?

- aquatic vertebrate with gills
- appendages in form of fins
- skin with scales of dermal origin
- gnathostomes


jaw evolution in Gnathostomes

- jaws formed from the gill supports (gill arches)
- considerable anatomical evidence supports idea-relics of this transformation are seen during development of modern sharks


characteristics of appendages in Chondrichthyes

paired pectoral and pelvic appendages


Chondrichthyes skeleton

- a living endoskeleton, no need to molt
- is totally cartilaginous
- cartilaginous skeleton is secondarily derived, since ancestors of sharks had true bone
- skeleton can grow with the organism