Deuterostomia

Question 1

What are the 3 phyla of Deuterostomia?

Answer 1

Hemichordata, Echinodermata, Chordata

Question 2

Shared characteristics of Deuterostomia?

Answer 2

Deuterostome embryo development:
- raidial, indeterminate cleavage
- anus forms first from blastopore
- Coelom forms from outpocketing of mesoderm from archenteron

Question 3

Which non-Deuterostomia undergo deuterostome development?

Answer 3

Brachiopoda and Ectoprota

Question 4

What are the 5 characteristics of Echinoderms?

Answer 4

Radial symmetry in adults
Epidermis covers exoskeleton of ossicles
Unique water vascular system
Diffuse nervous system, no centralized brain
Separate sexes, broadcast spawners

Question 5

What are ossicles?

Answer 5

calcareous plates which may have spines embedded in the dermis
the body wall can contain 1000s of ossicles

Question 6

How does the water vascular system of echinoderms work?

Answer 6

• Derived from the coelom and consists of a ring canal in the central disk and a network of hydraulic canals running down each arm
• radial canals branch into hundreds of fluid-filled, muscular tube feet that can be adapted for locomotion, feeding, respiration etc
• tube feet are controlled by water pressure acting on the ampulla and podium allowing them to attach to substrates via suction and adhesive mucus production
• water vascular system is connected to sea water via a porous ossicle called the madreoporite
• system also used for circulation and respiration
• gas exchange occurs through gills and diffusion through feet

Question 7

What is the structure of echnioderm nervous system?

Answer 7

A central disk with a nerve rung and radial nerves extending into the arms

Question 8

How do echinoderms reproduce?

Answer 8

Gametes are released into the water for external fertilization
- no parental care of planktonic larvae
- in some species males free-spawn and female retains and broods eggs

Question 9

What are the 5 clades of Echinodermata?

Answer 9

Crinoidea, Asteroidea, Ophiuroidea, Echinoidea, Holothuroidea

Question 10

Asteroidea characteristics? anatomy? feeding? reproduction?

Answer 10

• 5 or more arms radiating from central disk
• each arm has tube feet on its undersurface to grip substrate
• predators that feed by prying open molluscs with tube feet
• evert stomach onto prey to engulf and digest food
• reproduce asexually via fission of central disk
• can regenerate lost arms

Question 11

Echinoidea characteristics? Anatomy? Movement? Feeding?

Answer 11

• no arms, 5 rows of tube feet
• slow-moving, use spines (jointed ossicles) for locomotion and protection
• herbivorous, use jaw-like plates around mouth to grasp and grind algae

Question 12

Holothuroidea characteristics? Anatomy? Symmetry? Feeding?

Answer 12

• tube-shaped and secondarily bilaterally symmetrical
• rows of tube feet along body
• may have tube feet around mouth as feeding tentacles
• detritivores; deposit or filter feeders
• no external spines, reduced endoskeleton with scattered osicles

Question 13

What 3 groups are Chordates made of?

Answer 13

Vertebrata, Cephalochordata, Urochordata

Question 14

Shared derived characteristics of Chordata (4)?

Answer 14

Notochord
Dorsal, hollow nerve cord
Pharyngeal slits
Muscular, post-anal tail

Question 15

What is the notochord, how is it formed and what does it do?

Answer 15

Longitudinal, flexible rod located dorsally between digestive tract and nerve cord
- provides flexible skeletal support throughout the length of invertebrate chordates
- forms during embryogenesis when organ systems develop from embryonic layers

Question 16

Do vertebrates have a notochord, explain?

Answer 16

Vertebral column replaces notochord before birth
- embryonic notochord retained as parts of the vertebral discs between vertebrae

Question 17

How is the dorsal, hollow nerve cord developed?

Answer 17

• signalling molecules secreted by notochord and mesodermal cells induce neural plate formation from ectoderm
• neural plate curves inward forming the neural tube which develops into the CNS
• found ony in chordates, others have centrally located, hollow nerve cords

Question 18

What are pharyngeal slits and what do they do?

Answer 18

embryonic arches in the pharynx
- in invertebrates they function as filter-feeding structures
- in aquatic vertebrates they facilitate gas exchange as gills develop along the pharyngeal arch and are ventilated when water is forced through gill slits
- allow water entering mouth to exit, preventing it from entering digestive tract
- only present during embryonic development in tetrapods

Question 19

What kind of segmentation is present in Chordates and which group lacks it?

Answer 19

Not in Urochordata
- segmentally arranged muscle blocks in adult chordates develop from blockes of mesoderm called somites which flank the notochord
- arranged in chevron patterns
- alternating contractions of muscle blocks cause the notochord or vertebral column to flex side-side

Question 20

Cephalochordata characteristics? Anatomy? Feeding? Relationships?

Answer 20

• blade-like body shape, resemble bony fish but are invertebrates
• sedentary suspension feeders
• wiggle backwards into sand and draw water into mouth via ciliary action
• particles extracted using mucus-covered pharyngeal slits
• mucus net and food is ingested
• water exits body through atriopore
• retain chordate body plan as adults

Question 21

Urochordata characteristics? Movement? Relationships? development? anatomy? feeding? reproduction?

Answer 21

• more closely related to vertebrates
• larval stages have chordate body plan
• sessile suspension feeders either free-floating (pelagic) or attached to substrate
• after brief swimming phase, larvae attach to substrate by the head and metamorphose into sessile form
• adults have tough polysachharide tunic
• draw water in through incurrent siphon and filter through mucus-covered pharyngeal basket which collects food particles
• water exits through excurrent siphon
• may reproduce asexually by budding