Phylum Hemichordata and Chordata

Question 1

Do Hemichordates share deuterostome characteristics with echinoderms and chordates?

Answer 1

Yes

Question 2

Characteristics of the Phylum Hemichordata

Answer 2

-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

Question 3

What are the 2 classes of Hemichordata

Answer 3

-Class Enteropneusta (acorn worms)
-Class Pterobranchia

Question 4

What class of hemichordates live in burrows or under stones in mud or sand flats?

Answer 4

Class Enteropneusta or Acorn worms

Question 5

In Class Enteropneusta, mucous covered body in what three regions?

Answer 5

Proboscis
Collar
Trunk

Question 6

Describe Branchial system in Class Enteropneusta

Answer 6

-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

Question 7

-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

Answer 7

Class Pterobranchia

Question 8

What are the 5 characteristics of Phylum Chordata?

Answer 8

-notochord
-dorsal tubular nerve chord
-pharyngeal pouches and slits
-endostyle or thyroid gland
-postanal tail

Question 9

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

Answer 9

Notochord

Question 10

What replaces notochords in most adults in phylum chordata

Answer 10

bone or cartilage

Question 11

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

Answer 11

Dorsal Tubular nerve cord

Question 12

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

Answer 12

Pharyngeal slits or pouches

Question 13

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

Answer 13

Endostyle or Thyroid Gland

Question 14

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

Answer 14

Postanal tail

Question 15

Describe Subphylum Urochordata

Answer 15

-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

Question 16

What are the “root-like” extensions of tunic, help to anchor to substrate or connect individuals of colony

Answer 16

Stolons

Question 17

In Subphylum Urochordata, feeding involves _____?

Answer 17

endostyle; a ventral ciliated groove

Question 18

Describe feeding in Subphylum Urochordata

Answer 18

-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

Question 19

Free-swimming tadpole-like larva forms only have two chordate characters but adult urochordates have more

True/False

Answer 19

False; Adults urochordates have two but free-swimming tadpole-like larva forms have more

Question 20

Larva settles to substrate via _____?

Answer 20

adhesive papillae
-Outer epidermis shrinks – pulls notochord/tail structures internally
-Internal structures rotate 180° - digestive tract bends into U-shape

Question 21

Lancelets are in what Subphylum?

Answer 21

Subphylum Cephalochordata

Question 22

Lancelets show ___ chordate characteristics

Answer 22

4

Question 23

Subphylum Cephalochordata has what type of circulatory system?

Answer 23

-Closed circulatory system very similar to fish but no true heart
-Blood moved by contractile waves in walls of major vessels

Question 24

Subphylum Vertebrata are in ____phyletic group?

Answer 24

Vertebrates are monophyletic group

Question 25

Give some Musculoskeletal Modifications of Subphylum Vertebrata

Answer 25

Most with endoskeleton of cartilage or bone
Cranium
Vertebrae or rudimentary vertebrae

Question 26

Give some physiology upgrade of Subphylum Vertebrata

Answer 26

-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

Question 27

New Head, Brain and Sensory Systems of Vertebrates

Answer 27

-Parallels switch from filter-feeding to active predation
-Anterior nerve cord enlarged into tripartite brain
-Evolution of paired special sense organs for distance reception

Question 28

Development of head and sense organs mainly attributed to ________ and ________

Answer 28

-neural crest
-ectodermal placodes

Question 29

Neural crest consists of

Answer 29

-cranium
-pharyngeal skeleton
-tooth dentine
-endocrine glands

Question 30

Ectodermal placodes consists of

Answer 30

-olfactory epithelium -lens of eye
-inner ear epithelium
-some ganglia and cranial nerves
-lateral-line receptors -electroreceptors

Question 31

The Earliest Vertebrates
that are:
-Jawless, armoured with bone in dermis
-No paired fins
-Filter-feeders with muscular, pumping pharynx

Answer 31

Ostracoderms

Question 32

What are the three groups of ostracoderms?

Answer 32

-Osteostracans
-Heterostracans
-Anapsids

Question 33

Which group of ostracoderms have:
-Paired pectoral fins
-Heavy dermal boney armour with single head shield
-Sophisticated nervous system

Answer 33

Osteostracans

Question 34

Which group of ostracoderms are:
-likely poor swimmers
-Maybe filter-feeders; muscular pharynx suggests predation on soft-bodies animals

Answer 34

Heterostracans

Question 35

Which group of ostracoderms are more streamlined

Answer 35

Anapsids

Question 36

What was one of the most significant events in vertebrate evolution?

Answer 36

Origin of jaws

Question 37

What species are the early Jawed Vertebrates

Answer 37

-Placoderms
-Acanthodians