Phylum Hemichordata and Chordata Flashcards
Do Hemichordates share deuterostome characteristics with echinoderms and chordates?
Yes
Characteristics of the Phylum Hemichordata
-Marine, deuterostomes – body divided into proboscis, collar and trunk; coelom with three cavities
-Ciliated pharyngeal slits
-Open circulatory system
-Complete digestive tract
-Dorsal (sometimes tubular) nerve cord
What are the 2 classes of Hemichordata
-Class Enteropneusta (acorn worms)
-Class Pterobranchia
What class of hemichordates live in burrows or under stones in mud or sand flats?
Class Enteropneusta or Acorn worms
In Class Enteropneusta, mucous covered body in what three regions?
Proboscis
Collar
Trunk
Describe Branchial system in Class Enteropneusta
-Gill pores open from ciliated gill chambers > connect to u-shaped gill slits in side of pharynx
-No gills on gill slits; some gas exchange via branchial epithelium and skin
-Similar structure to enteropneusts (proboscis, collar, trunk) but some structural differences reflect sedentary lifestyle
-Live in secreted tubes
-Branching arms with tentacles with ciliated grooves
Class Pterobranchia
What are the 5 characteristics of Phylum Chordata?
-notochord
-dorsal tubular nerve chord
-pharyngeal pouches and slits
-endostyle or thyroid gland
-postanal tail
Characteristic of Chordate that:
-is a supportive rod
-made of connective tissue sheath surrounding cells with large fluid-filled vacuoles
-resists anteroposterior axis compression
-allows lateral bending
Notochord
What replaces notochords in most adults in phylum chordata
bone or cartilage
Characteristic of Chordate that:
-is the main reason for vertebrae success
-runs along longitudinal axis of body, dorsal to notochord
-usually expands anteriorly as brain
-forms central nervous system
Dorsal Tubular nerve cord
Characteristic of Chordate:
-openings between pharyngeal region of digestive tract and outside of body
-earliest chordate used them for filter feeding (some modern ones still do)
-other chordates developed gills in pharyngeal pouches for gas exchange
Pharyngeal slits or pouches
What is the characteristic of Chordate that:
-occurs in all chordates but no other animals (found in protochordates and lamprey larvae)
-secretes mucus; traps food
Endostyle or Thyroid Gland
What is the characteristic of Chordate that:
-Extends posteriorly beyond anal opening
-Evolved for propulsion in water
-Either notochord or vertebral column support tail
-Present only in embryonic forms in many chordates
Postanal tail
Describe Subphylum Urochordata
-Tunicates or sea squirts
-Most sessile, some free-living
-Body wall made of connective-tissue-like covering
-Many with sac-like bodies lined with mantle
What are the “root-like” extensions of tunic, help to anchor to substrate or connect individuals of colony
Stolons
In Subphylum Urochordata, feeding involves _____?
endostyle; a ventral ciliated groove
Describe feeding in Subphylum Urochordata
-Endostyle forms mucous sheet
-Food gets trapped in mucous sheet and incorporated into mucous string that is moved to gut via cilia
-Digestive enzymes in stomach added to food
Free-swimming tadpole-like larva forms only have two chordate characters but adult urochordates have more
True/False
False; Adults urochordates have two but free-swimming tadpole-like larva forms have more
Larva settles to substrate via _____?
adhesive papillae
-Outer epidermis shrinks – pulls notochord/tail structures internally
-Internal structures rotate 180° - digestive tract bends into U-shape
Lancelets are in what Subphylum?
Subphylum Cephalochordata
Lancelets show ___ chordate characteristics
4
Subphylum Cephalochordata has what type of circulatory system?
-Closed circulatory system very similar to fish but no true heart
-Blood moved by contractile waves in walls of major vessels
Subphylum Vertebrata are in ____phyletic group?
Vertebrates are monophyletic group
Give some Musculoskeletal Modifications of Subphylum Vertebrata
Most with endoskeleton of cartilage or bone
Cranium
Vertebrae or rudimentary vertebrae
Give some physiology upgrade of Subphylum Vertebrata
-Addition of muscles to pharynx
-Highly vascularized gills
-Muscular gut instead of gut thatuses ciliary action
-Specialized digestive glands > liver, pancreas
-Chambered heart, RBCs with hemoglobin
-Paired glomerular kidneys
New Head, Brain and Sensory Systems of Vertebrates
-Parallels switch from filter-feeding to active predation
-Anterior nerve cord enlarged into tripartite brain
-Evolution of paired special sense organs for distance reception
Development of head and sense organs mainly attributed to ________ and ________
-neural crest
-ectodermal placodes
Neural crest consists of
-cranium
-pharyngeal skeleton
-tooth dentine
-endocrine glands
Ectodermal placodes consists of
-olfactory epithelium -lens of eye
-inner ear epithelium
-some ganglia and cranial nerves
-lateral-line receptors -electroreceptors
The Earliest Vertebrates
that are:
-Jawless, armoured with bone in dermis
-No paired fins
-Filter-feeders with muscular, pumping pharynx
Ostracoderms
What are the three groups of ostracoderms?
-Osteostracans
-Heterostracans
-Anapsids
Which group of ostracoderms have:
-Paired pectoral fins
-Heavy dermal boney armour with single head shield
-Sophisticated nervous system
Osteostracans
Which group of ostracoderms are:
-likely poor swimmers
-Maybe filter-feeders; muscular pharynx suggests predation on soft-bodies animals
Heterostracans
Which group of ostracoderms are more streamlined
Anapsids
What was one of the most significant events in vertebrate evolution?
Origin of jaws
What species are the early Jawed Vertebrates
-Placoderms
-Acanthodians
